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[unleashed.git] / kernel / os / kmem.c

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 * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
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/*
 * Kernel memory allocator, as described in the following two papers and a
 * statement about the consolidator:
 *
 * Jeff Bonwick,
 * The Slab Allocator: An Object-Caching Kernel Memory Allocator.
 * Proceedings of the Summer 1994 Usenix Conference.
 * Available as /shared/sac/PSARC/1994/028/materials/kmem.pdf.
 *
 * Jeff Bonwick and Jonathan Adams,
 * Magazines and vmem: Extending the Slab Allocator to Many CPUs and
 * Arbitrary Resources.
 * Proceedings of the 2001 Usenix Conference.
 * Available as /shared/sac/PSARC/2000/550/materials/vmem.pdf.
 *
 * kmem Slab Consolidator Big Theory Statement:
 *
 * 1. Motivation
 *
 * As stated in Bonwick94, slabs provide the following advantages over other
 * allocation structures in terms of memory fragmentation:
 *
 *  - Internal fragmentation (per-buffer wasted space) is minimal.
 *  - Severe external fragmentation (unused buffers on the free list) is
 *    unlikely.
 *
 * Segregating objects by size eliminates one source of external fragmentation,
 * and according to Bonwick:
 *
 *   The other reason that slabs reduce external fragmentation is that all
 *   objects in a slab are of the same type, so they have the same lifetime
 *   distribution. The resulting segregation of short-lived and long-lived
 *   objects at slab granularity reduces the likelihood of an entire page being
 *   held hostage due to a single long-lived allocation [Barrett93, Hanson90].
 *
 * While unlikely, severe external fragmentation remains possible. Clients that
 * allocate both short- and long-lived objects from the same cache cannot
 * anticipate the distribution of long-lived objects within the allocator's slab
 * implementation. Even a small percentage of long-lived objects distributed
 * randomly across many slabs can lead to a worst case scenario where the client
 * frees the majority of its objects and the system gets back almost none of the
 * slabs. Despite the client doing what it reasonably can to help the system
 * reclaim memory, the allocator cannot shake free enough slabs because of
 * lonely allocations stubbornly hanging on. Although the allocator is in a
 * position to diagnose the fragmentation, there is nothing that the allocator
 * by itself can do about it. It only takes a single allocated object to prevent
 * an entire slab from being reclaimed, and any object handed out by
 * kmem_cache_alloc() is by definition in the client's control. Conversely,
 * although the client is in a position to move a long-lived object, it has no
 * way of knowing if the object is causing fragmentation, and if so, where to
 * move it. A solution necessarily requires further cooperation between the
 * allocator and the client.
 *
 * 2. Move Callback
 *
 * The kmem slab consolidator therefore adds a move callback to the
 * allocator/client interface, improving worst-case external fragmentation in
 * kmem caches that supply a function to move objects from one memory location
 * to another. In a situation of low memory kmem attempts to consolidate all of
 * a cache's slabs at once; otherwise it works slowly to bring external
 * fragmentation within the 1/8 limit guaranteed for internal fragmentation,
 * thereby helping to avoid a low memory situation in the future.
 *
 * The callback has the following signature:
 *
 *   kmem_cbrc_t move(void *old, void *new, size_t size, void *user_arg)
 *
 * It supplies the kmem client with two addresses: the allocated object that
 * kmem wants to move and a buffer selected by kmem for the client to use as the
 * copy destination. The callback is kmem's way of saying "Please get off of
 * this buffer and use this one instead." kmem knows where it wants to move the
 * object in order to best reduce fragmentation. All the client needs to know
 * about the second argument (void *new) is that it is an allocated, constructed
 * object ready to take the contents of the old object. When the move function
 * is called, the system is likely to be low on memory, and the new object
 * spares the client from having to worry about allocating memory for the
 * requested move. The third argument supplies the size of the object, in case a
 * single move function handles multiple caches whose objects differ only in
 * size (such as zio_buf_512, zio_buf_1024, etc). Finally, the same optional
 * user argument passed to the constructor, destructor, and reclaim functions is
 * also passed to the move callback.
 *
 * 2.1 Setting the Move Callback
 *
 * The client sets the move callback after creating the cache and before
 * allocating from it:
 *
 *      object_cache = kmem_cache_create(...);
 *      kmem_cache_set_move(object_cache, object_move);
 *
 * 2.2 Move Callback Return Values
 *
 * Only the client knows about its own data and when is a good time to move it.
 * The client is cooperating with kmem to return unused memory to the system,
 * and kmem respectfully accepts this help at the client's convenience. When
 * asked to move an object, the client can respond with any of the following:
 *
 *   typedef enum kmem_cbrc {
 *           KMEM_CBRC_YES,
 *           KMEM_CBRC_NO,
 *           KMEM_CBRC_LATER,
 *           KMEM_CBRC_DONT_NEED,
 *           KMEM_CBRC_DONT_KNOW
 *   } kmem_cbrc_t;
 *
 * The client must not explicitly kmem_cache_free() either of the objects passed
 * to the callback, since kmem wants to free them directly to the slab layer
 * (bypassing the per-CPU magazine layer). The response tells kmem which of the
 * objects to free:
 *
 *       YES: (Did it) The client moved the object, so kmem frees the old one.
 *        NO: (Never) The client refused, so kmem frees the new object (the
 *            unused copy destination). kmem also marks the slab of the old
 *            object so as not to bother the client with further callbacks for
 *            that object as long as the slab remains on the partial slab list.
 *            (The system won't be getting the slab back as long as the
 *            immovable object holds it hostage, so there's no point in moving
 *            any of its objects.)
 *     LATER: The client is using the object and cannot move it now, so kmem
 *            frees the new object (the unused copy destination). kmem still
 *            attempts to move other objects off the slab, since it expects to
 *            succeed in clearing the slab in a later callback. The client
 *            should use LATER instead of NO if the object is likely to become
 *            movable very soon.
 * DONT_NEED: The client no longer needs the object, so kmem frees the old along
 *            with the new object (the unused copy destination). This response
 *            is the client's opportunity to be a model citizen and give back as
 *            much as it can.
 * DONT_KNOW: The client does not know about the object because
 *            a) the client has just allocated the object and not yet put it
 *               wherever it expects to find known objects
 *            b) the client has removed the object from wherever it expects to
 *               find known objects and is about to free it, or
 *            c) the client has freed the object.
 *            In all these cases (a, b, and c) kmem frees the new object (the
 *            unused copy destination).  In the first case, the object is in
 *            use and the correct action is that for LATER; in the latter two
 *            cases, we know that the object is either freed or about to be
 *            freed, in which case it is either already in a magazine or about
 *            to be in one.  In these cases, we know that the object will either
 *            be reallocated and reused, or it will end up in a full magazine
 *            that will be reaped (thereby liberating the slab).  Because it
 *            is prohibitively expensive to differentiate these cases, and
 *            because the defrag code is executed when we're low on memory
 *            (thereby biasing the system to reclaim full magazines) we treat
 *            all DONT_KNOW cases as LATER and rely on cache reaping to
 *            generally clean up full magazines.  While we take the same action
 *            for these cases, we maintain their semantic distinction:  if
 *            defragmentation is not occurring, it is useful to know if this
 *            is due to objects in use (LATER) or objects in an unknown state
 *            of transition (DONT_KNOW).
 *
 * 2.3 Object States
 *
 * Neither kmem nor the client can be assumed to know the object's whereabouts
 * at the time of the callback. An object belonging to a kmem cache may be in
 * any of the following states:
 *
 * 1. Uninitialized on the slab
 * 2. Allocated from the slab but not constructed (still uninitialized)
 * 3. Allocated from the slab, constructed, but not yet ready for business
 *    (not in a valid state for the move callback)
 * 4. In use (valid and known to the client)
 * 5. About to be freed (no longer in a valid state for the move callback)
 * 6. Freed to a magazine (still constructed)
 * 7. Allocated from a magazine, not yet ready for business (not in a valid
 *    state for the move callback), and about to return to state #4
 * 8. Deconstructed on a magazine that is about to be freed
 * 9. Freed to the slab
 *
 * Since the move callback may be called at any time while the object is in any
 * of the above states (except state #1), the client needs a safe way to
 * determine whether or not it knows about the object. Specifically, the client
 * needs to know whether or not the object is in state #4, the only state in
 * which a move is valid. If the object is in any other state, the client should
 * immediately return KMEM_CBRC_DONT_KNOW, since it is unsafe to access any of
 * the object's fields.
 *
 * Note that although an object may be in state #4 when kmem initiates the move
 * request, the object may no longer be in that state by the time kmem actually
 * calls the move function. Not only does the client free objects
 * asynchronously, kmem itself puts move requests on a queue where thay are
 * pending until kmem processes them from another context. Also, objects freed
 * to a magazine appear allocated from the point of view of the slab layer, so
 * kmem may even initiate requests for objects in a state other than state #4.
 *
 * 2.3.1 Magazine Layer
 *
 * An important insight revealed by the states listed above is that the magazine
 * layer is populated only by kmem_cache_free(). Magazines of constructed
 * objects are never populated directly from the slab layer (which contains raw,
 * unconstructed objects). Whenever an allocation request cannot be satisfied
 * from the magazine layer, the magazines are bypassed and the request is
 * satisfied from the slab layer (creating a new slab if necessary). kmem calls
 * the object constructor only when allocating from the slab layer, and only in
 * response to kmem_cache_alloc() or to prepare the destination buffer passed in
 * the move callback. kmem does not preconstruct objects in anticipation of
 * kmem_cache_alloc().
 *
 * 2.3.2 Object Constructor and Destructor
 *
 * If the client supplies a destructor, it must be valid to call the destructor
 * on a newly created object (immediately after the constructor).
 *
 * 2.4 Recognizing Known Objects
 *
 * There is a simple test to determine safely whether or not the client knows
 * about a given object in the move callback. It relies on the fact that kmem
 * guarantees that the object of the move callback has only been touched by the
 * client itself or else by kmem. kmem does this by ensuring that none of the
 * cache's slabs are freed to the virtual memory (VM) subsystem while a move
 * callback is pending. When the last object on a slab is freed, if there is a
 * pending move, kmem puts the slab on a per-cache dead list and defers freeing
 * slabs on that list until all pending callbacks are completed. That way,
 * clients can be certain that the object of a move callback is in one of the
 * states listed above, making it possible to distinguish known objects (in
 * state #4) using the two low order bits of any pointer member (with the
 * exception of 'char *' or 'short *' which may not be 4-byte aligned on some
 * platforms).
 *
 * The test works as long as the client always transitions objects from state #4
 * (known, in use) to state #5 (about to be freed, invalid) by setting the low
 * order bit of the client-designated pointer member. Since kmem only writes
 * invalid memory patterns, such as 0xbaddcafe to uninitialized memory and
 * 0xdeadbeef to freed memory, any scribbling on the object done by kmem is
 * guaranteed to set at least one of the two low order bits. Therefore, given an
 * object with a back pointer to a 'container_t *o_container', the client can
 * test
 *
 *      container_t *container = object->o_container;
 *      if ((uintptr_t)container & 0x3) {
 *              return (KMEM_CBRC_DONT_KNOW);
 *      }
 *
 * Typically, an object will have a pointer to some structure with a list or
 * hash where objects from the cache are kept while in use. Assuming that the
 * client has some way of knowing that the container structure is valid and will
 * not go away during the move, and assuming that the structure includes a lock
 * to protect whatever collection is used, then the client would continue as
 * follows:
 *
 *      // Ensure that the container structure does not go away.
 *      if (container_hold(container) == 0) {
 *              return (KMEM_CBRC_DONT_KNOW);
 *      }
 *      mutex_enter(&container->c_objects_lock);
 *      if (container != object->o_container) {
 *              mutex_exit(&container->c_objects_lock);
 *              container_rele(container);
 *              return (KMEM_CBRC_DONT_KNOW);
 *      }
 *
 * At this point the client knows that the object cannot be freed as long as
 * c_objects_lock is held. Note that after acquiring the lock, the client must
 * recheck the o_container pointer in case the object was removed just before
 * acquiring the lock.
 *
 * When the client is about to free an object, it must first remove that object
 * from the list, hash, or other structure where it is kept. At that time, to
 * mark the object so it can be distinguished from the remaining, known objects,
 * the client sets the designated low order bit:
 *
 *      mutex_enter(&container->c_objects_lock);
 *      object->o_container = (void *)((uintptr_t)object->o_container | 0x1);
 *      list_remove(&container->c_objects, object);
 *      mutex_exit(&container->c_objects_lock);
 *
 * In the common case, the object is freed to the magazine layer, where it may
 * be reused on a subsequent allocation without the overhead of calling the
 * constructor. While in the magazine it appears allocated from the point of
 * view of the slab layer, making it a candidate for the move callback. Most
 * objects unrecognized by the client in the move callback fall into this
 * category and are cheaply distinguished from known objects by the test
 * described earlier. Because searching magazines is prohibitively expensive
 * for kmem, clients that do not mark freed objects (and therefore return
 * KMEM_CBRC_DONT_KNOW for large numbers of objects) may find defragmentation
 * efficacy reduced.
 *
 * Invalidating the designated pointer member before freeing the object marks
 * the object to be avoided in the callback, and conversely, assigning a valid
 * value to the designated pointer member after allocating the object makes the
 * object fair game for the callback:
 *
 *      ... allocate object ...
 *      ... set any initial state not set by the constructor ...
 *
 *      mutex_enter(&container->c_objects_lock);
 *      list_insert_tail(&container->c_objects, object);
 *      membar_producer();
 *      object->o_container = container;
 *      mutex_exit(&container->c_objects_lock);
 *
 * Note that everything else must be valid before setting o_container makes the
 * object fair game for the move callback. The membar_producer() call ensures
 * that all the object's state is written to memory before setting the pointer
 * that transitions the object from state #3 or #7 (allocated, constructed, not
 * yet in use) to state #4 (in use, valid). That's important because the move
 * function has to check the validity of the pointer before it can safely
 * acquire the lock protecting the collection where it expects to find known
 * objects.
 *
 * This method of distinguishing known objects observes the usual symmetry:
 * invalidating the designated pointer is the first thing the client does before
 * freeing the object, and setting the designated pointer is the last thing the
 * client does after allocating the object. Of course, the client is not
 * required to use this method. Fundamentally, how the client recognizes known
 * objects is completely up to the client, but this method is recommended as an
 * efficient and safe way to take advantage of the guarantees made by kmem. If
 * the entire object is arbitrary data without any markable bits from a suitable
 * pointer member, then the client must find some other method, such as
 * searching a hash table of known objects.
 *
 * 2.5 Preventing Objects From Moving
 *
 * Besides a way to distinguish known objects, the other thing that the client
 * needs is a strategy to ensure that an object will not move while the client
 * is actively using it. The details of satisfying this requirement tend to be
 * highly cache-specific. It might seem that the same rules that let a client
 * remove an object safely should also decide when an object can be moved
 * safely. However, any object state that makes a removal attempt invalid is
 * likely to be long-lasting for objects that the client does not expect to
 * remove. kmem knows nothing about the object state and is equally likely (from
 * the client's point of view) to request a move for any object in the cache,
 * whether prepared for removal or not. Even a low percentage of objects stuck
 * in place by unremovability will defeat the consolidator if the stuck objects
 * are the same long-lived allocations likely to hold slabs hostage.
 * Fundamentally, the consolidator is not aimed at common cases. Severe external
 * fragmentation is a worst case scenario manifested as sparsely allocated
 * slabs, by definition a low percentage of the cache's objects. When deciding
 * what makes an object movable, keep in mind the goal of the consolidator: to
 * bring worst-case external fragmentation within the limits guaranteed for
 * internal fragmentation. Removability is a poor criterion if it is likely to
 * exclude more than an insignificant percentage of objects for long periods of
 * time.
 *
 * A tricky general solution exists, and it has the advantage of letting you
 * move any object at almost any moment, practically eliminating the likelihood
 * that an object can hold a slab hostage. However, if there is a cache-specific
 * way to ensure that an object is not actively in use in the vast majority of
 * cases, a simpler solution that leverages this cache-specific knowledge is
 * preferred.
 *
 * 2.5.1 Cache-Specific Solution
 *
 * As an example of a cache-specific solution, the ZFS znode cache takes
 * advantage of the fact that the vast majority of znodes are only being
 * referenced from the DNLC. (A typical case might be a few hundred in active
 * use and a hundred thousand in the DNLC.) In the move callback, after the ZFS
 * client has established that it recognizes the znode and can access its fields
 * safely (using the method described earlier), it then tests whether the znode
 * is referenced by anything other than the DNLC. If so, it assumes that the
 * znode may be in active use and is unsafe to move, so it drops its locks and
 * returns KMEM_CBRC_LATER. The advantage of this strategy is that everywhere
 * else znodes are used, no change is needed to protect against the possibility
 * of the znode moving. The disadvantage is that it remains possible for an
 * application to hold a znode slab hostage with an open file descriptor.
 * However, this case ought to be rare and the consolidator has a way to deal
 * with it: If the client responds KMEM_CBRC_LATER repeatedly for the same
 * object, kmem eventually stops believing it and treats the slab as if the
 * client had responded KMEM_CBRC_NO. Having marked the hostage slab, kmem can
 * then focus on getting it off of the partial slab list by allocating rather
 * than freeing all of its objects. (Either way of getting a slab off the
 * free list reduces fragmentation.)
 *
 * 2.5.2 General Solution
 *
 * The general solution, on the other hand, requires an explicit hold everywhere
 * the object is used to prevent it from moving. To keep the client locking
 * strategy as uncomplicated as possible, kmem guarantees the simplifying
 * assumption that move callbacks are sequential, even across multiple caches.
 * Internally, a global queue processed by a single thread supports all caches
 * implementing the callback function. No matter how many caches supply a move
 * function, the consolidator never moves more than one object at a time, so the
 * client does not have to worry about tricky lock ordering involving several
 * related objects from different kmem caches.
 *
 * The general solution implements the explicit hold as a read-write lock, which
 * allows multiple readers to access an object from the cache simultaneously
 * while a single writer is excluded from moving it. A single rwlock for the
 * entire cache would lock out all threads from using any of the cache's objects
 * even though only a single object is being moved, so to reduce contention,
 * the client can fan out the single rwlock into an array of rwlocks hashed by
 * the object address, making it probable that moving one object will not
 * prevent other threads from using a different object. The rwlock cannot be a
 * member of the object itself, because the possibility of the object moving
 * makes it unsafe to access any of the object's fields until the lock is
 * acquired.
 *
 * Assuming a small, fixed number of locks, it's possible that multiple objects
 * will hash to the same lock. A thread that needs to use multiple objects in
 * the same function may acquire the same lock multiple times. Since rwlocks are
 * reentrant for readers, and since there is never more than a single writer at
 * a time (assuming that the client acquires the lock as a writer only when
 * moving an object inside the callback), there would seem to be no problem.
 * However, a client locking multiple objects in the same function must handle
 * one case of potential deadlock: Assume that thread A needs to prevent both
 * object 1 and object 2 from moving, and thread B, the callback, meanwhile
 * tries to move object 3. It's possible, if objects 1, 2, and 3 all hash to the
 * same lock, that thread A will acquire the lock for object 1 as a reader
 * before thread B sets the lock's write-wanted bit, preventing thread A from
 * reacquiring the lock for object 2 as a reader. Unable to make forward
 * progress, thread A will never release the lock for object 1, resulting in
 * deadlock.
 *
 * There are two ways of avoiding the deadlock just described. The first is to
 * use rw_tryenter() rather than rw_enter() in the callback function when
 * attempting to acquire the lock as a writer. If tryenter discovers that the
 * same object (or another object hashed to the same lock) is already in use, it
 * aborts the callback and returns KMEM_CBRC_LATER. The second way is to use
 * rprwlock_t (declared in kernel/fs/zfs/sys/rprwlock.h) instead of rwlock_t,
 * since it allows a thread to acquire the lock as a reader in spite of a
 * waiting writer. This second approach insists on moving the object now, no
 * matter how many readers the move function must wait for in order to do so,
 * and could delay the completion of the callback indefinitely (blocking
 * callbacks to other clients). In practice, a less insistent callback using
 * rw_tryenter() returns KMEM_CBRC_LATER infrequently enough that there seems
 * little reason to use anything else.
 *
 * Avoiding deadlock is not the only problem that an implementation using an
 * explicit hold needs to solve. Locking the object in the first place (to
 * prevent it from moving) remains a problem, since the object could move
 * between the time you obtain a pointer to the object and the time you acquire
 * the rwlock hashed to that pointer value. Therefore the client needs to
 * recheck the value of the pointer after acquiring the lock, drop the lock if
 * the value has changed, and try again. This requires a level of indirection:
 * something that points to the object rather than the object itself, that the
 * client can access safely while attempting to acquire the lock. (The object
 * itself cannot be referenced safely because it can move at any time.)
 * The following lock-acquisition function takes whatever is safe to reference
 * (arg), follows its pointer to the object (using function f), and tries as
 * often as necessary to acquire the hashed lock and verify that the object
 * still has not moved:
 *
 *      object_t *
 *      object_hold(object_f f, void *arg)
 *      {
 *              object_t *op;
 *
 *              op = f(arg);
 *              if (op == NULL) {
 *                      return (NULL);
 *              }
 *
 *              rw_enter(OBJECT_RWLOCK(op), RW_READER);
 *              while (op != f(arg)) {
 *                      rw_exit(OBJECT_RWLOCK(op));
 *                      op = f(arg);
 *                      if (op == NULL) {
 *                              break;
 *                      }
 *                      rw_enter(OBJECT_RWLOCK(op), RW_READER);
 *              }
 *
 *              return (op);
 *      }
 *
 * The OBJECT_RWLOCK macro hashes the object address to obtain the rwlock. The
 * lock reacquisition loop, while necessary, almost never executes. The function
 * pointer f (used to obtain the object pointer from arg) has the following type
 * definition:
 *
 *      typedef object_t *(*object_f)(void *arg);
 *
 * An object_f implementation is likely to be as simple as accessing a structure
 * member:
 *
 *      object_t *
 *      s_object(void *arg)
 *      {
 *              something_t *sp = arg;
 *              return (sp->s_object);
 *      }
 *
 * The flexibility of a function pointer allows the path to the object to be
 * arbitrarily complex and also supports the notion that depending on where you
 * are using the object, you may need to get it from someplace different.
 *
 * The function that releases the explicit hold is simpler because it does not
 * have to worry about the object moving:
 *
 *      void
 *      object_rele(object_t *op)
 *      {
 *              rw_exit(OBJECT_RWLOCK(op));
 *      }
 *
 * The caller is spared these details so that obtaining and releasing an
 * explicit hold feels like a simple mutex_enter()/mutex_exit() pair. The caller
 * of object_hold() only needs to know that the returned object pointer is valid
 * if not NULL and that the object will not move until released.
 *
 * Although object_hold() prevents an object from moving, it does not prevent it
 * from being freed. The caller must take measures before calling object_hold()
 * (afterwards is too late) to ensure that the held object cannot be freed. The
 * caller must do so without accessing the unsafe object reference, so any lock
 * or reference count used to ensure the continued existence of the object must
 * live outside the object itself.
 *
 * Obtaining a new object is a special case where an explicit hold is impossible
 * for the caller. Any function that returns a newly allocated object (either as
 * a return value, or as an in-out paramter) must return it already held; after
 * the caller gets it is too late, since the object cannot be safely accessed
 * without the level of indirection described earlier. The following
 * object_alloc() example uses the same code shown earlier to transition a new
 * object into the state of being recognized (by the client) as a known object.
 * The function must acquire the hold (rw_enter) before that state transition
 * makes the object movable:
 *
 *      static object_t *
 *      object_alloc(container_t *container)
 *      {
 *              object_t *object = kmem_cache_alloc(object_cache, 0);
 *              ... set any initial state not set by the constructor ...
 *              rw_enter(OBJECT_RWLOCK(object), RW_READER);
 *              mutex_enter(&container->c_objects_lock);
 *              list_insert_tail(&container->c_objects, object);
 *              membar_producer();
 *              object->o_container = container;
 *              mutex_exit(&container->c_objects_lock);
 *              return (object);
 *      }
 *
 * Functions that implicitly acquire an object hold (any function that calls
 * object_alloc() to supply an object for the caller) need to be carefully noted
 * so that the matching object_rele() is not neglected. Otherwise, leaked holds
 * prevent all objects hashed to the affected rwlocks from ever being moved.
 *
 * The pointer to a held object can be hashed to the holding rwlock even after
 * the object has been freed. Although it is possible to release the hold
 * after freeing the object, you may decide to release the hold implicitly in
 * whatever function frees the object, so as to release the hold as soon as
 * possible, and for the sake of symmetry with the function that implicitly
 * acquires the hold when it allocates the object. Here, object_free() releases
 * the hold acquired by object_alloc(). Its implicit object_rele() forms a
 * matching pair with object_hold():
 *
 *      void
 *      object_free(object_t *object)
 *      {
 *              container_t *container;
 *
 *              ASSERT(object_held(object));
 *              container = object->o_container;
 *              mutex_enter(&container->c_objects_lock);
 *              object->o_container =
 *                  (void *)((uintptr_t)object->o_container | 0x1);
 *              list_remove(&container->c_objects, object);
 *              mutex_exit(&container->c_objects_lock);
 *              object_rele(object);
 *              kmem_cache_free(object_cache, object);
 *      }
 *
 * Note that object_free() cannot safely accept an object pointer as an argument
 * unless the object is already held. Any function that calls object_free()
 * needs to be carefully noted since it similarly forms a matching pair with
 * object_hold().
 *
 * To complete the picture, the following callback function implements the
 * general solution by moving objects only if they are currently unheld:
 *
 *      static kmem_cbrc_t
 *      object_move(void *buf, void *newbuf, size_t size, void *arg)
 *      {
 *              object_t *op = buf, *np = newbuf;
 *              container_t *container;
 *
 *              container = op->o_container;
 *              if ((uintptr_t)container & 0x3) {
 *                      return (KMEM_CBRC_DONT_KNOW);
 *              }
 *
 *              // Ensure that the container structure does not go away.
 *              if (container_hold(container) == 0) {
 *                      return (KMEM_CBRC_DONT_KNOW);
 *              }
 *
 *              mutex_enter(&container->c_objects_lock);
 *              if (container != op->o_container) {
 *                      mutex_exit(&container->c_objects_lock);
 *                      container_rele(container);
 *                      return (KMEM_CBRC_DONT_KNOW);
 *              }
 *
 *              if (rw_tryenter(OBJECT_RWLOCK(op), RW_WRITER) == 0) {
 *                      mutex_exit(&container->c_objects_lock);
 *                      container_rele(container);
 *                      return (KMEM_CBRC_LATER);
 *              }
 *
 *              object_move_impl(op, np); // critical section
 *              rw_exit(OBJECT_RWLOCK(op));
 *
 *              op->o_container = (void *)((uintptr_t)op->o_container | 0x1);
 *              list_link_replace(&op->o_link_node, &np->o_link_node);
 *              mutex_exit(&container->c_objects_lock);
 *              container_rele(container);
 *              return (KMEM_CBRC_YES);
 *      }
 *
 * Note that object_move() must invalidate the designated o_container pointer of
 * the old object in the same way that object_free() does, since kmem will free
 * the object in response to the KMEM_CBRC_YES return value.
 *
 * The lock order in object_move() differs from object_alloc(), which locks
 * OBJECT_RWLOCK first and &container->c_objects_lock second, but as long as the
 * callback uses rw_tryenter() (preventing the deadlock described earlier), it's
 * not a problem. Holding the lock on the object list in the example above
 * through the entire callback not only prevents the object from going away, it
 * also allows you to lock the list elsewhere and know that none of its elements
 * will move during iteration.
 *
 * Adding an explicit hold everywhere an object from the cache is used is tricky
 * and involves much more change to client code than a cache-specific solution
 * that leverages existing state to decide whether or not an object is
 * movable. However, this approach has the advantage that no object remains
 * immovable for any significant length of time, making it extremely unlikely
 * that long-lived allocations can continue holding slabs hostage; and it works
 * for any cache.
 *
 * 3. Consolidator Implementation
 *
 * Once the client supplies a move function that a) recognizes known objects and
 * b) avoids moving objects that are actively in use, the remaining work is up
 * to the consolidator to decide which objects to move and when to issue
 * callbacks.
 *
 * The consolidator relies on the fact that a cache's slabs are ordered by
 * usage. Each slab has a fixed number of objects. Depending on the slab's
 * "color" (the offset of the first object from the beginning of the slab;
 * offsets are staggered to mitigate false sharing of cache lines) it is either
 * the maximum number of objects per slab determined at cache creation time or
 * else the number closest to the maximum that fits within the space remaining
 * after the initial offset. A completely allocated slab may contribute some
 * internal fragmentation (per-slab overhead) but no external fragmentation, so
 * it is of no interest to the consolidator. At the other extreme, slabs whose
 * objects have all been freed to the slab are released to the virtual memory
 * (VM) subsystem (objects freed to magazines are still allocated as far as the
 * slab is concerned). External fragmentation exists when there are slabs
 * somewhere between these extremes. A partial slab has at least one but not all
 * of its objects allocated. The more partial slabs, and the fewer allocated
 * objects on each of them, the higher the fragmentation. Hence the
 * consolidator's overall strategy is to reduce the number of partial slabs by
 * moving allocated objects from the least allocated slabs to the most allocated
 * slabs.
 *
 * Partial slabs are kept in an AVL tree ordered by usage. Completely allocated
 * slabs are kept separately in an unordered list. Since the majority of slabs
 * tend to be completely allocated (a typical unfragmented cache may have
 * thousands of complete slabs and only a single partial slab), separating
 * complete slabs improves the efficiency of partial slab ordering, since the
 * complete slabs do not affect the depth or balance of the AVL tree. This
 * ordered sequence of partial slabs acts as a "free list" supplying objects for
 * allocation requests.
 *
 * Objects are always allocated from the first partial slab in the free list,
 * where the allocation is most likely to eliminate a partial slab (by
 * completely allocating it). Conversely, when a single object from a completely
 * allocated slab is freed to the slab, that slab is added to the front of the
 * free list. Since most free list activity involves highly allocated slabs
 * coming and going at the front of the list, slabs tend naturally toward the
 * ideal order: highly allocated at the front, sparsely allocated at the back.
 * Slabs with few allocated objects are likely to become completely free if they
 * keep a safe distance away from the front of the free list. Slab misorders
 * interfere with the natural tendency of slabs to become completely free or
 * completely allocated. For example, a slab with a single allocated object
 * needs only a single free to escape the cache; its natural desire is
 * frustrated when it finds itself at the front of the list where a second
 * allocation happens just before the free could have released it. Another slab
 * with all but one object allocated might have supplied the buffer instead, so
 * that both (as opposed to neither) of the slabs would have been taken off the
 * free list.
 *
 * Although slabs tend naturally toward the ideal order, misorders allowed by a
 * simple list implementation defeat the consolidator's strategy of merging
 * least- and most-allocated slabs. Without an AVL tree to guarantee order, kmem
 * needs another way to fix misorders to optimize its callback strategy. One
 * approach is to periodically scan a limited number of slabs, advancing a
 * marker to hold the current scan position, and to move extreme misorders to
 * the front or back of the free list and to the front or back of the current
 * scan range. By making consecutive scan ranges overlap by one slab, the least
 * allocated slab in the current range can be carried along from the end of one
 * scan to the start of the next.
 *
 * Maintaining partial slabs in an AVL tree relieves kmem of this additional
 * task, however. Since most of the cache's activity is in the magazine layer,
 * and allocations from the slab layer represent only a startup cost, the
 * overhead of maintaining a balanced tree is not a significant concern compared
 * to the opportunity of reducing complexity by eliminating the partial slab
 * scanner just described. The overhead of an AVL tree is minimized by
 * maintaining only partial slabs in the tree and keeping completely allocated
 * slabs separately in a list. To avoid increasing the size of the slab
 * structure the AVL linkage pointers are reused for the slab's list linkage,
 * since the slab will always be either partial or complete, never stored both
 * ways at the same time. To further minimize the overhead of the AVL tree the
 * compare function that orders partial slabs by usage divides the range of
 * allocated object counts into bins such that counts within the same bin are
 * considered equal. Binning partial slabs makes it less likely that allocating
 * or freeing a single object will change the slab's order, requiring a tree
 * reinsertion (an avl_remove() followed by an avl_add(), both potentially
 * requiring some rebalancing of the tree). Allocation counts closest to
 * completely free and completely allocated are left unbinned (finely sorted) to
 * better support the consolidator's strategy of merging slabs at either
 * extreme.
 *
 * 3.1 Assessing Fragmentation and Selecting Candidate Slabs
 *
 * The consolidator piggybacks on the kmem maintenance thread and is called on
 * the same interval as kmem_cache_update(), once per cache every fifteen
 * seconds. kmem maintains a running count of unallocated objects in the slab
 * layer (cache_bufslab). The consolidator checks whether that number exceeds
 * 12.5% (1/8) of the total objects in the cache (cache_buftotal), and whether
 * there is a significant number of slabs in the cache (arbitrarily a minimum
 * 101 total slabs). Unused objects that have fallen out of the magazine layer's
 * working set are included in the assessment, and magazines in the depot are
 * reaped if those objects would lift cache_bufslab above the fragmentation
 * threshold. Once the consolidator decides that a cache is fragmented, it looks
 * for a candidate slab to reclaim, starting at the end of the partial slab free
 * list and scanning backwards. At first the consolidator is choosy: only a slab
 * with fewer than 12.5% (1/8) of its objects allocated qualifies (or else a
 * single allocated object, regardless of percentage). If there is difficulty
 * finding a candidate slab, kmem raises the allocation threshold incrementally,
 * up to a maximum 87.5% (7/8), so that eventually the consolidator will reduce
 * external fragmentation (unused objects on the free list) below 12.5% (1/8),
 * even in the worst case of every slab in the cache being almost 7/8 allocated.
 * The threshold can also be lowered incrementally when candidate slabs are easy
 * to find, and the threshold is reset to the minimum 1/8 as soon as the cache
 * is no longer fragmented.
 *
 * 3.2 Generating Callbacks
 *
 * Once an eligible slab is chosen, a callback is generated for every allocated
 * object on the slab, in the hope that the client will move everything off the
 * slab and make it reclaimable. Objects selected as move destinations are
 * chosen from slabs at the front of the free list. Assuming slabs in the ideal
 * order (most allocated at the front, least allocated at the back) and a
 * cooperative client, the consolidator will succeed in removing slabs from both
 * ends of the free list, completely allocating on the one hand and completely
 * freeing on the other. Objects selected as move destinations are allocated in
 * the kmem maintenance thread where move requests are enqueued. A separate
 * callback thread removes pending callbacks from the queue and calls the
 * client. The separate thread ensures that client code (the move function) does
 * not interfere with internal kmem maintenance tasks. A map of pending
 * callbacks keyed by object address (the object to be moved) is checked to
 * ensure that duplicate callbacks are not generated for the same object.
 * Allocating the move destination (the object to move to) prevents subsequent
 * callbacks from selecting the same destination as an earlier pending callback.
 *
 * Move requests can also be generated by kmem_cache_reap() when the system is
 * desperate for memory and by kmem_cache_move_notify(), called by the client to
 * notify kmem that a move refused earlier with KMEM_CBRC_LATER is now possible.
 * The map of pending callbacks is protected by the same lock that protects the
 * slab layer.
 *
 * When the system is desperate for memory, kmem does not bother to determine
 * whether or not the cache exceeds the fragmentation threshold, but tries to
 * consolidate as many slabs as possible. Normally, the consolidator chews
 * slowly, one sparsely allocated slab at a time during each maintenance
 * interval that the cache is fragmented. When desperate, the consolidator
 * starts at the last partial slab and enqueues callbacks for every allocated
 * object on every partial slab, working backwards until it reaches the first
 * partial slab. The first partial slab, meanwhile, advances in pace with the
 * consolidator as allocations to supply move destinations for the enqueued
 * callbacks use up the highly allocated slabs at the front of the free list.
 * Ideally, the overgrown free list collapses like an accordion, starting at
 * both ends and ending at the center with a single partial slab.
 *
 * 3.3 Client Responses
 *
 * When the client returns KMEM_CBRC_NO in response to the move callback, kmem
 * marks the slab that supplied the stuck object non-reclaimable and moves it to
 * front of the free list. The slab remains marked as long as it remains on the
 * free list, and it appears more allocated to the partial slab compare function
 * than any unmarked slab, no matter how many of its objects are allocated.
 * Since even one immovable object ties up the entire slab, the goal is to
 * completely allocate any slab that cannot be completely freed. kmem does not
 * bother generating callbacks to move objects from a marked slab unless the
 * system is desperate.
 *
 * When the client responds KMEM_CBRC_LATER, kmem increments a count for the
 * slab. If the client responds LATER too many times, kmem disbelieves and
 * treats the response as a NO. The count is cleared when the slab is taken off
 * the partial slab list or when the client moves one of the slab's objects.
 *
 * 4. Observability
 *
 * A kmem cache's external fragmentation is best observed with 'mdb -k' using
 * the ::kmem_slabs dcmd. For a complete description of the command, enter
 * '::help kmem_slabs' at the mdb prompt.
 */

#include <sys/kmem_impl.h>
#include <sys/vmem_impl.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/vm.h>
#include <sys/proc.h>
#include <sys/tuneable.h>
#include <sys/systm.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/sdt.h>
#include <sys/mutex.h>
#include <sys/bitmap.h>
#include <sys/atomic.h>
#include <sys/kobj.h>
#include <sys/disp.h>
#include <vm/seg_kmem.h>
#include <sys/log.h>
#include <sys/callb.h>
#include <sys/taskq.h>
#include <sys/modctl.h>
#include <sys/reboot.h>
#include <sys/id32.h>
#include <sys/zone.h>
#include <sys/netstack.h>
#ifdef  DEBUG
#include <sys/random.h>
#endif

extern void streams_msg_init(void);
extern int segkp_fromheap;
extern void segkp_cache_free(void);
extern int callout_init_done;

struct kmem_cache_kstat {
        kstat_named_t   kmc_buf_size;
        kstat_named_t   kmc_align;
        kstat_named_t   kmc_chunk_size;
        kstat_named_t   kmc_slab_size;
        kstat_named_t   kmc_alloc;
        kstat_named_t   kmc_alloc_fail;
        kstat_named_t   kmc_free;
        kstat_named_t   kmc_depot_alloc;
        kstat_named_t   kmc_depot_free;
        kstat_named_t   kmc_depot_contention;
        kstat_named_t   kmc_slab_alloc;
        kstat_named_t   kmc_slab_free;
        kstat_named_t   kmc_buf_constructed;
        kstat_named_t   kmc_buf_avail;
        kstat_named_t   kmc_buf_inuse;
        kstat_named_t   kmc_buf_total;
        kstat_named_t   kmc_buf_max;
        kstat_named_t   kmc_slab_create;
        kstat_named_t   kmc_slab_destroy;
        kstat_named_t   kmc_vmem_source;
        kstat_named_t   kmc_hash_size;
        kstat_named_t   kmc_hash_lookup_depth;
        kstat_named_t   kmc_hash_rescale;
        kstat_named_t   kmc_full_magazines;
        kstat_named_t   kmc_empty_magazines;
        kstat_named_t   kmc_magazine_size;
        kstat_named_t   kmc_reap; /* number of kmem_cache_reap() calls */
        kstat_named_t   kmc_defrag; /* attempts to defrag all partial slabs */
        kstat_named_t   kmc_scan; /* attempts to defrag one partial slab */
        kstat_named_t   kmc_move_callbacks; /* sum of yes, no, later, dn, dk */
        kstat_named_t   kmc_move_yes;
        kstat_named_t   kmc_move_no;
        kstat_named_t   kmc_move_later;
        kstat_named_t   kmc_move_dont_need;
        kstat_named_t   kmc_move_dont_know; /* obj unrecognized by client ... */
        kstat_named_t   kmc_move_hunt_found; /* ... but found in mag layer */
        kstat_named_t   kmc_move_slabs_freed; /* slabs freed by consolidator */
        kstat_named_t   kmc_move_reclaimable; /* buffers, if consolidator ran */
} kmem_cache_kstat = {
        { "buf_size",           KSTAT_DATA_UINT64 },
        { "align",              KSTAT_DATA_UINT64 },
        { "chunk_size",         KSTAT_DATA_UINT64 },
        { "slab_size",          KSTAT_DATA_UINT64 },
        { "alloc",              KSTAT_DATA_UINT64 },
        { "alloc_fail",         KSTAT_DATA_UINT64 },
        { "free",               KSTAT_DATA_UINT64 },
        { "depot_alloc",        KSTAT_DATA_UINT64 },
        { "depot_free",         KSTAT_DATA_UINT64 },
        { "depot_contention",   KSTAT_DATA_UINT64 },
        { "slab_alloc",         KSTAT_DATA_UINT64 },
        { "slab_free",          KSTAT_DATA_UINT64 },
        { "buf_constructed",    KSTAT_DATA_UINT64 },
        { "buf_avail",          KSTAT_DATA_UINT64 },
        { "buf_inuse",          KSTAT_DATA_UINT64 },
        { "buf_total",          KSTAT_DATA_UINT64 },
        { "buf_max",            KSTAT_DATA_UINT64 },
        { "slab_create",        KSTAT_DATA_UINT64 },
        { "slab_destroy",       KSTAT_DATA_UINT64 },
        { "vmem_source",        KSTAT_DATA_UINT64 },
        { "hash_size",          KSTAT_DATA_UINT64 },
        { "hash_lookup_depth",  KSTAT_DATA_UINT64 },
        { "hash_rescale",       KSTAT_DATA_UINT64 },
        { "full_magazines",     KSTAT_DATA_UINT64 },
        { "empty_magazines",    KSTAT_DATA_UINT64 },
        { "magazine_size",      KSTAT_DATA_UINT64 },
        { "reap",               KSTAT_DATA_UINT64 },
        { "defrag",             KSTAT_DATA_UINT64 },
        { "scan",               KSTAT_DATA_UINT64 },
        { "move_callbacks",     KSTAT_DATA_UINT64 },
        { "move_yes",           KSTAT_DATA_UINT64 },
        { "move_no",            KSTAT_DATA_UINT64 },
        { "move_later",         KSTAT_DATA_UINT64 },
        { "move_dont_need",     KSTAT_DATA_UINT64 },
        { "move_dont_know",     KSTAT_DATA_UINT64 },
        { "move_hunt_found",    KSTAT_DATA_UINT64 },
        { "move_slabs_freed",   KSTAT_DATA_UINT64 },
        { "move_reclaimable",   KSTAT_DATA_UINT64 },
};

static kmutex_t kmem_cache_kstat_lock;

/*
 * The default set of caches to back kmem_alloc().
 * These sizes should be reevaluated periodically.
 *
 * We want allocations that are multiples of the coherency granularity
 * (64 bytes) to be satisfied from a cache which is a multiple of 64
 * bytes, so that it will be 64-byte aligned.  For all multiples of 64,
 * the next kmem_cache_size greater than or equal to it must be a
 * multiple of 64.
 *
 * We split the table into two sections:  size <= 4k and size > 4k.  This
 * saves a lot of space and cache footprint in our cache tables.
 */
static const int kmem_alloc_sizes[] = {
        1 * 8,
        2 * 8,
        3 * 8,
        4 * 8,          5 * 8,          6 * 8,          7 * 8,
        4 * 16,         5 * 16,         6 * 16,         7 * 16,
        4 * 32,         5 * 32,         6 * 32,         7 * 32,
        4 * 64,         5 * 64,         6 * 64,         7 * 64,
        4 * 128,        5 * 128,        6 * 128,        7 * 128,
        P2ALIGN(8192 / 7, 64),
        P2ALIGN(8192 / 6, 64),
        P2ALIGN(8192 / 5, 64),
        P2ALIGN(8192 / 4, 64),
        P2ALIGN(8192 / 3, 64),
        P2ALIGN(8192 / 2, 64),
};

static const int kmem_big_alloc_sizes[] = {
        2 * 4096,       3 * 4096,
        2 * 8192,       3 * 8192,
        4 * 8192,       5 * 8192,       6 * 8192,       7 * 8192,
        8 * 8192,       9 * 8192,       10 * 8192,      11 * 8192,
        12 * 8192,      13 * 8192,      14 * 8192,      15 * 8192,
        16 * 8192
};

#define KMEM_MAXBUF             4096
#define KMEM_BIG_MAXBUF_32BIT   32768
#define KMEM_BIG_MAXBUF         131072

#define KMEM_BIG_MULTIPLE       4096    /* big_alloc_sizes must be a multiple */
#define KMEM_BIG_SHIFT          12      /* lg(KMEM_BIG_MULTIPLE) */

static kmem_cache_t *kmem_alloc_table[KMEM_MAXBUF >> KMEM_ALIGN_SHIFT];
static kmem_cache_t *kmem_big_alloc_table[KMEM_BIG_MAXBUF >> KMEM_BIG_SHIFT];

#define KMEM_ALLOC_TABLE_MAX    (KMEM_MAXBUF >> KMEM_ALIGN_SHIFT)
static size_t kmem_big_alloc_table_max = 0;     /* # of filled elements */

static kmem_magtype_t kmem_magtype[] = {
        { 1,    8,      3200,   65536   },
        { 3,    16,     256,    32768   },
        { 7,    32,     64,     16384   },
        { 15,   64,     0,      8192    },
        { 31,   64,     0,      4096    },
        { 47,   64,     0,      2048    },
        { 63,   64,     0,      1024    },
        { 95,   64,     0,      512     },
        { 143,  64,     0,      0       },
};

static uint32_t kmem_reaping;
static uint32_t kmem_reaping_idspace;

/*
 * kmem tunables
 */
clock_t kmem_reap_interval;     /* cache reaping rate [15 * HZ ticks] */
int kmem_depot_contention = 3;  /* max failed tryenters per real interval */
pgcnt_t kmem_reapahead = 0;     /* start reaping N pages before pageout */
int kmem_panic = 1;             /* whether to panic on error */
int kmem_logging = 1;           /* kmem_log_enter() override */
uint32_t kmem_mtbf = 0;         /* mean time between failures [default: off] */
size_t kmem_transaction_log_size; /* transaction log size [2% of memory] */
size_t kmem_content_log_size;   /* content log size [2% of memory] */
size_t kmem_failure_log_size;   /* failure log [4 pages per CPU] */
size_t kmem_slab_log_size;      /* slab create log [4 pages per CPU] */
size_t kmem_content_maxsave = 256; /* KMF_CONTENTS max bytes to log */
size_t kmem_lite_minsize = 0;   /* minimum buffer size for KMF_LITE */
size_t kmem_lite_maxalign = 1024; /* maximum buffer alignment for KMF_LITE */
int kmem_lite_pcs = 4;          /* number of PCs to store in KMF_LITE mode */
size_t kmem_maxverify;          /* maximum bytes to inspect in debug routines */
size_t kmem_minfirewall;        /* hardware-enforced redzone threshold */

#ifdef _LP64
size_t  kmem_max_cached = KMEM_BIG_MAXBUF;      /* maximum kmem_alloc cache */
#else
size_t  kmem_max_cached = KMEM_BIG_MAXBUF_32BIT; /* maximum kmem_alloc cache */
#endif

#ifdef DEBUG
int kmem_flags = KMF_AUDIT | KMF_DEADBEEF | KMF_REDZONE | KMF_CONTENTS;
#else
int kmem_flags = 0;
#endif
int kmem_ready;

static kmem_cache_t     *kmem_slab_cache;
static kmem_cache_t     *kmem_bufctl_cache;
static kmem_cache_t     *kmem_bufctl_audit_cache;

static kmutex_t         kmem_cache_lock;        /* inter-cache linkage only */
static list_t           kmem_caches;

static taskq_t          *kmem_taskq;
static kmutex_t         kmem_flags_lock;
static vmem_t           *kmem_metadata_arena;
static vmem_t           *kmem_msb_arena;        /* arena for metadata caches */
static vmem_t           *kmem_cache_arena;
static vmem_t           *kmem_hash_arena;
static vmem_t           *kmem_log_arena;
static vmem_t           *kmem_oversize_arena;
static vmem_t           *kmem_va_arena;
static vmem_t           *kmem_default_arena;
static vmem_t           *kmem_firewall_va_arena;
static vmem_t           *kmem_firewall_arena;

/*
 * kmem slab consolidator thresholds (tunables)
 */
size_t kmem_frag_minslabs = 101;        /* minimum total slabs */
size_t kmem_frag_numer = 1;             /* free buffers (numerator) */
size_t kmem_frag_denom = KMEM_VOID_FRACTION; /* buffers (denominator) */
/*
 * Maximum number of slabs from which to move buffers during a single
 * maintenance interval while the system is not low on memory.
 */
size_t kmem_reclaim_max_slabs = 1;
/*
 * Number of slabs to scan backwards from the end of the partial slab list
 * when searching for buffers to relocate.
 */
size_t kmem_reclaim_scan_range = 12;

/* consolidator knobs */
boolean_t kmem_move_noreap;
boolean_t kmem_move_blocked;
boolean_t kmem_move_fulltilt;
boolean_t kmem_move_any_partial;

#ifdef  DEBUG
/*
 * kmem consolidator debug tunables:
 * Ensure code coverage by occasionally running the consolidator even when the
 * caches are not fragmented (they may never be). These intervals are mean time
 * in cache maintenance intervals (kmem_cache_update).
 */
uint32_t kmem_mtb_move = 60;    /* defrag 1 slab (~15min) */
uint32_t kmem_mtb_reap = 1800;  /* defrag all slabs (~7.5hrs) */
#endif  /* DEBUG */

static kmem_cache_t     *kmem_defrag_cache;
static kmem_cache_t     *kmem_move_cache;
static taskq_t          *kmem_move_taskq;

static void kmem_cache_scan(kmem_cache_t *);
static void kmem_cache_defrag(kmem_cache_t *);
static void kmem_slab_prefill(kmem_cache_t *, kmem_slab_t *);


kmem_log_header_t       *kmem_transaction_log;
kmem_log_header_t       *kmem_content_log;
kmem_log_header_t       *kmem_failure_log;
kmem_log_header_t       *kmem_slab_log;

static int              kmem_lite_count; /* # of PCs in kmem_buftag_lite_t */

#define KMEM_BUFTAG_LITE_ENTER(bt, count, caller)                       \
        if ((count) > 0) {                                              \
                pc_t *_s = ((kmem_buftag_lite_t *)(bt))->bt_history;    \
                pc_t *_e;                                               \
                /* memmove() the old entries down one notch */          \
                for (_e = &_s[(count) - 1]; _e > _s; _e--)              \
                        *_e = *(_e - 1);                                \
                *_s = (uintptr_t)(caller);                              \
        }

#define KMERR_MODIFIED  0       /* buffer modified while on freelist */
#define KMERR_REDZONE   1       /* redzone violation (write past end of buf) */
#define KMERR_DUPFREE   2       /* freed a buffer twice */
#define KMERR_BADADDR   3       /* freed a bad (unallocated) address */
#define KMERR_BADBUFTAG 4       /* buftag corrupted */
#define KMERR_BADBUFCTL 5       /* bufctl corrupted */
#define KMERR_BADCACHE  6       /* freed a buffer to the wrong cache */
#define KMERR_BADSIZE   7       /* alloc size != free size */
#define KMERR_BADBASE   8       /* buffer base address wrong */

struct {
        hrtime_t        kmp_timestamp;  /* timestamp of panic */
        int             kmp_error;      /* type of kmem error */
        void            *kmp_buffer;    /* buffer that induced panic */
        void            *kmp_realbuf;   /* real start address for buffer */
        kmem_cache_t    *kmp_cache;     /* buffer's cache according to client */
        kmem_cache_t    *kmp_realcache; /* actual cache containing buffer */
        kmem_slab_t     *kmp_slab;      /* slab accoring to kmem_findslab() */
        kmem_bufctl_t   *kmp_bufctl;    /* bufctl */
} kmem_panic_info;


static void
copy_pattern(uint64_t pattern, void *buf_arg, size_t size)
{
        uint64_t *bufend = (uint64_t *)((char *)buf_arg + size);
        uint64_t *buf = buf_arg;

        while (buf < bufend)
                *buf++ = pattern;
}

static void *
verify_pattern(uint64_t pattern, void *buf_arg, size_t size)
{
        uint64_t *bufend = (uint64_t *)((char *)buf_arg + size);
        uint64_t *buf;

        for (buf = buf_arg; buf < bufend; buf++)
                if (*buf != pattern)
                        return (buf);
        return (NULL);
}

static void *
verify_and_copy_pattern(uint64_t old, uint64_t new, void *buf_arg, size_t size)
{
        uint64_t *bufend = (uint64_t *)((char *)buf_arg + size);
        uint64_t *buf;

        for (buf = buf_arg; buf < bufend; buf++) {
                if (*buf != old) {
                        copy_pattern(old, buf_arg,
                            (char *)buf - (char *)buf_arg);
                        return (buf);
                }
                *buf = new;
        }

        return (NULL);
}

static void
kmem_cache_applyall(void (*func)(kmem_cache_t *), taskq_t *tq, int tqflag)
{
        kmem_cache_t *cp;

        mutex_enter(&kmem_cache_lock);
        for (cp = list_head(&kmem_caches); cp != NULL;
            cp = list_next(&kmem_caches, cp))
                if (tq != NULL)
                        (void) taskq_dispatch(tq, (task_func_t *)func, cp,
                            tqflag);
                else
                        func(cp);
        mutex_exit(&kmem_cache_lock);
}

static void
kmem_cache_applyall_id(void (*func)(kmem_cache_t *), taskq_t *tq, int tqflag)
{
        kmem_cache_t *cp;

        mutex_enter(&kmem_cache_lock);
        for (cp = list_head(&kmem_caches); cp != NULL;
            cp = list_next(&kmem_caches, cp)) {
                if (!(cp->cache_cflags & KMC_IDENTIFIER))
                        continue;
                if (tq != NULL)
                        (void) taskq_dispatch(tq, (task_func_t *)func, cp,
                            tqflag);
                else
                        func(cp);
        }
        mutex_exit(&kmem_cache_lock);
}

/*
 * Debugging support.  Given a buffer address, find its slab.
 */
static kmem_slab_t *
kmem_findslab(kmem_cache_t *cp, void *buf)
{
        kmem_slab_t *sp;

        mutex_enter(&cp->cache_lock);
        for (sp = list_head(&cp->cache_complete_slabs); sp != NULL;
            sp = list_next(&cp->cache_complete_slabs, sp)) {
                if (KMEM_SLAB_MEMBER(sp, buf)) {
                        mutex_exit(&cp->cache_lock);
                        return (sp);
                }
        }
        for (sp = avl_first(&cp->cache_partial_slabs); sp != NULL;
            sp = AVL_NEXT(&cp->cache_partial_slabs, sp)) {
                if (KMEM_SLAB_MEMBER(sp, buf)) {
                        mutex_exit(&cp->cache_lock);
                        return (sp);
                }
        }
        mutex_exit(&cp->cache_lock);

        return (NULL);
}

static void
kmem_error(int error, kmem_cache_t *cparg, void *bufarg)
{
        kmem_buftag_t *btp = NULL;
        kmem_bufctl_t *bcp = NULL;
        kmem_cache_t *cp = cparg;
        kmem_slab_t *sp;
        uint64_t *off;
        void *buf = bufarg;

        kmem_logging = 0;       /* stop logging when a bad thing happens */

        kmem_panic_info.kmp_timestamp = gethrtime();

        sp = kmem_findslab(cp, buf);
        if (sp == NULL) {
                for (cp = list_tail(&kmem_caches); cp != NULL;
                    cp = list_prev(&kmem_caches, cp)) {
                        if ((sp = kmem_findslab(cp, buf)) != NULL)
                                break;
                }
        }

        if (sp == NULL) {
                cp = NULL;
                error = KMERR_BADADDR;
        } else {
                if (cp != cparg)
                        error = KMERR_BADCACHE;
                else
                        buf = (char *)bufarg - ((uintptr_t)bufarg -
                            (uintptr_t)sp->slab_base) % cp->cache_chunksize;
                if (buf != bufarg)
                        error = KMERR_BADBASE;
                if (cp->cache_flags & KMF_BUFTAG)
                        btp = KMEM_BUFTAG(cp, buf);
                if (cp->cache_flags & KMF_HASH) {
                        mutex_enter(&cp->cache_lock);
                        for (bcp = *KMEM_HASH(cp, buf); bcp; bcp = bcp->bc_next)
                                if (bcp->bc_addr == buf)
                                        break;
                        mutex_exit(&cp->cache_lock);
                        if (bcp == NULL && btp != NULL)
                                bcp = btp->bt_bufctl;
                        if (kmem_findslab(cp->cache_bufctl_cache, bcp) ==
                            NULL || P2PHASE((uintptr_t)bcp, KMEM_ALIGN) ||
                            bcp->bc_addr != buf) {
                                error = KMERR_BADBUFCTL;
                                bcp = NULL;
                        }
                }
        }

        kmem_panic_info.kmp_error = error;
        kmem_panic_info.kmp_buffer = bufarg;
        kmem_panic_info.kmp_realbuf = buf;
        kmem_panic_info.kmp_cache = cparg;
        kmem_panic_info.kmp_realcache = cp;
        kmem_panic_info.kmp_slab = sp;
        kmem_panic_info.kmp_bufctl = bcp;

        printf("kernel memory allocator: ");

        switch (error) {

        case KMERR_MODIFIED:
                printf("buffer modified after being freed\n");
                off = verify_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
                if (off == NULL)        /* shouldn't happen */
                        off = buf;
                printf("modification occurred at offset 0x%lx "
                    "(0x%llx replaced by 0x%llx)\n",
                    (uintptr_t)off - (uintptr_t)buf,
                    (longlong_t)KMEM_FREE_PATTERN, (longlong_t)*off);
                break;

        case KMERR_REDZONE:
                printf("redzone violation: write past end of buffer\n");
                break;

        case KMERR_BADADDR:
                printf("invalid free: buffer not in cache\n");
                break;

        case KMERR_DUPFREE:
                printf("duplicate free: buffer freed twice\n");
                break;

        case KMERR_BADBUFTAG:
                printf("boundary tag corrupted\n");
                printf("bcp ^ bxstat = %lx, should be %lx\n",
                    (intptr_t)btp->bt_bufctl ^ btp->bt_bxstat,
                    KMEM_BUFTAG_FREE);
                break;

        case KMERR_BADBUFCTL:
                printf("bufctl corrupted\n");
                break;

        case KMERR_BADCACHE:
                printf("buffer freed to wrong cache\n");
                printf("buffer was allocated from %s,\n", cp->cache_name);
                printf("caller attempting free to %s.\n", cparg->cache_name);
                break;

        case KMERR_BADSIZE:
                printf("bad free: free size (%u) != alloc size (%u)\n",
                    KMEM_SIZE_DECODE(((uint32_t *)btp)[0]),
                    KMEM_SIZE_DECODE(((uint32_t *)btp)[1]));
                break;

        case KMERR_BADBASE:
                printf("bad free: free address (%p) != alloc address (%p)\n",
                    bufarg, buf);
                break;
        }

        printf("buffer=%p  bufctl=%p  cache: %s\n",
            bufarg, (void *)bcp, cparg->cache_name);

        if (bcp != NULL && (cp->cache_flags & KMF_AUDIT) &&
            error != KMERR_BADBUFCTL) {
                int d;
                timestruc_t ts;
                kmem_bufctl_audit_t *bcap = (kmem_bufctl_audit_t *)bcp;

                hrt2ts(kmem_panic_info.kmp_timestamp - bcap->bc_timestamp, &ts);
                printf("previous transaction on buffer %p:\n", buf);
                printf("thread=%p  time=T-%ld.%09ld  slab=%p  cache: %s\n",
                    (void *)bcap->bc_thread, ts.tv_sec, ts.tv_nsec,
                    (void *)sp, cp->cache_name);
                for (d = 0; d < MIN(bcap->bc_depth, KMEM_STACK_DEPTH); d++) {
                        ulong_t off;
                        char *sym = kobj_getsymname(bcap->bc_stack[d], &off);
                        printf("%s+%lx\n", sym ? sym : "?", off);
                }
        }
        if (kmem_panic > 0)
                panic("kernel heap corruption detected");
        if (kmem_panic == 0)
                debug_enter(NULL);
        kmem_logging = 1;       /* resume logging */
}

static kmem_log_header_t *
kmem_log_init(size_t logsize)
{
        kmem_log_header_t *lhp;
        int nchunks = 4 * max_ncpus;
        size_t lhsize = (size_t)&((kmem_log_header_t *)0)->lh_cpu[max_ncpus];
        int i;

        /*
         * Make sure that lhp->lh_cpu[] is nicely aligned
         * to prevent false sharing of cache lines.
         */
        lhsize = P2ROUNDUP(lhsize, KMEM_ALIGN);
        lhp = vmem_xalloc(kmem_log_arena, lhsize, 64, P2NPHASE(lhsize, 64), 0,
            NULL, NULL, VM_SLEEP);
        bzero(lhp, lhsize);

        mutex_init(&lhp->lh_lock, NULL, MUTEX_DEFAULT, NULL);
        lhp->lh_nchunks = nchunks;
        lhp->lh_chunksize = P2ROUNDUP(logsize / nchunks + 1, PAGESIZE);
        lhp->lh_base = vmem_alloc(kmem_log_arena,
            lhp->lh_chunksize * nchunks, VM_SLEEP);
        lhp->lh_free = vmem_alloc(kmem_log_arena,
            nchunks * sizeof (int), VM_SLEEP);
        bzero(lhp->lh_base, lhp->lh_chunksize * nchunks);

        for (i = 0; i < max_ncpus; i++) {
                kmem_cpu_log_header_t *clhp = &lhp->lh_cpu[i];
                mutex_init(&clhp->clh_lock, NULL, MUTEX_DEFAULT, NULL);
                clhp->clh_chunk = i;
        }

        for (i = max_ncpus; i < nchunks; i++)
                lhp->lh_free[i] = i;

        lhp->lh_head = max_ncpus;
        lhp->lh_tail = 0;

        return (lhp);
}

static void *
kmem_log_enter(kmem_log_header_t *lhp, void *data, size_t size)
{
        void *logspace;
        kmem_cpu_log_header_t *clhp = &lhp->lh_cpu[CPU->cpu_seqid];

        if (lhp == NULL || kmem_logging == 0 || panicstr)
                return (NULL);

        mutex_enter(&clhp->clh_lock);
        clhp->clh_hits++;
        if (size > clhp->clh_avail) {
                mutex_enter(&lhp->lh_lock);
                lhp->lh_hits++;
                lhp->lh_free[lhp->lh_tail] = clhp->clh_chunk;
                lhp->lh_tail = (lhp->lh_tail + 1) % lhp->lh_nchunks;
                clhp->clh_chunk = lhp->lh_free[lhp->lh_head];
                lhp->lh_head = (lhp->lh_head + 1) % lhp->lh_nchunks;
                clhp->clh_current = lhp->lh_base +
                    clhp->clh_chunk * lhp->lh_chunksize;
                clhp->clh_avail = lhp->lh_chunksize;
                if (size > lhp->lh_chunksize)
                        size = lhp->lh_chunksize;
                mutex_exit(&lhp->lh_lock);
        }
        logspace = clhp->clh_current;
        clhp->clh_current += size;
        clhp->clh_avail -= size;
        bcopy(data, logspace, size);
        mutex_exit(&clhp->clh_lock);
        return (logspace);
}

#define KMEM_AUDIT(lp, cp, bcp)                                         \
{                                                                       \
        kmem_bufctl_audit_t *_bcp = (kmem_bufctl_audit_t *)(bcp);       \
        _bcp->bc_timestamp = gethrtime();                               \
        _bcp->bc_thread = curthread;                                    \
        _bcp->bc_depth = getpcstack(_bcp->bc_stack, KMEM_STACK_DEPTH);  \
        _bcp->bc_lastlog = kmem_log_enter((lp), _bcp, sizeof (*_bcp));  \
}

static void
kmem_log_event(kmem_log_header_t *lp, kmem_cache_t *cp,
    kmem_slab_t *sp, void *addr)
{
        kmem_bufctl_audit_t bca;

        bzero(&bca, sizeof (kmem_bufctl_audit_t));
        bca.bc_addr = addr;
        bca.bc_slab = sp;
        bca.bc_cache = cp;
        KMEM_AUDIT(lp, cp, &bca);
}

/*
 * Create a new slab for cache cp.
 */
static kmem_slab_t *
kmem_slab_create(kmem_cache_t *cp, int kmflag)
{
        size_t slabsize = cp->cache_slabsize;
        size_t chunksize = cp->cache_chunksize;
        int cache_flags = cp->cache_flags;
        size_t color, chunks;
        char *buf, *slab;
        kmem_slab_t *sp;
        kmem_bufctl_t *bcp;
        vmem_t *vmp = cp->cache_arena;

        ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));

        color = cp->cache_color + cp->cache_align;
        if (color > cp->cache_maxcolor)
                color = cp->cache_mincolor;
        cp->cache_color = color;

        slab = vmem_alloc(vmp, slabsize, kmflag & KM_VMFLAGS);

        if (slab == NULL)
                goto vmem_alloc_failure;

        ASSERT(P2PHASE((uintptr_t)slab, vmp->vm_quantum) == 0);

        /*
         * Reverify what was already checked in kmem_cache_set_move(), since the
         * consolidator depends (for correctness) on slabs being initialized
         * with the 0xbaddcafe memory pattern (setting a low order bit usable by
         * clients to distinguish uninitialized memory from known objects).
         */
        ASSERT((cp->cache_move == NULL) || !(cp->cache_cflags & KMC_NOTOUCH));
        if (!(cp->cache_cflags & KMC_NOTOUCH))
                copy_pattern(KMEM_UNINITIALIZED_PATTERN, slab, slabsize);

        if (cache_flags & KMF_HASH) {
                if ((sp = kmem_cache_alloc(kmem_slab_cache, kmflag)) == NULL)
                        goto slab_alloc_failure;
                chunks = (slabsize - color) / chunksize;
        } else {
                sp = KMEM_SLAB(cp, slab);
                chunks = (slabsize - sizeof (kmem_slab_t) - color) / chunksize;
        }

        sp->slab_cache  = cp;
        sp->slab_head   = NULL;
        sp->slab_refcnt = 0;
        sp->slab_base   = buf = slab + color;
        sp->slab_chunks = chunks;
        sp->slab_stuck_offset = (uint32_t)-1;
        sp->slab_later_count = 0;
        sp->slab_flags = 0;

        ASSERT(chunks > 0);
        while (chunks-- != 0) {
                if (cache_flags & KMF_HASH) {
                        bcp = kmem_cache_alloc(cp->cache_bufctl_cache, kmflag);
                        if (bcp == NULL)
                                goto bufctl_alloc_failure;
                        if (cache_flags & KMF_AUDIT) {
                                kmem_bufctl_audit_t *bcap =
                                    (kmem_bufctl_audit_t *)bcp;
                                bzero(bcap, sizeof (kmem_bufctl_audit_t));
                                bcap->bc_cache = cp;
                        }
                        bcp->bc_addr = buf;
                        bcp->bc_slab = sp;
                } else {
                        bcp = KMEM_BUFCTL(cp, buf);
                }
                if (cache_flags & KMF_BUFTAG) {
                        kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
                        btp->bt_redzone = KMEM_REDZONE_PATTERN;
                        btp->bt_bufctl = bcp;
                        btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_FREE;
                        if (cache_flags & KMF_DEADBEEF) {
                                copy_pattern(KMEM_FREE_PATTERN, buf,
                                    cp->cache_verify);
                        }
                }
                bcp->bc_next = sp->slab_head;
                sp->slab_head = bcp;
                buf += chunksize;
        }

        kmem_log_event(kmem_slab_log, cp, sp, slab);

        return (sp);

bufctl_alloc_failure:

        while ((bcp = sp->slab_head) != NULL) {
                sp->slab_head = bcp->bc_next;
                kmem_cache_free(cp->cache_bufctl_cache, bcp);
        }
        kmem_cache_free(kmem_slab_cache, sp);

slab_alloc_failure:

        vmem_free(vmp, slab, slabsize);

vmem_alloc_failure:

        kmem_log_event(kmem_failure_log, cp, NULL, NULL);
        atomic_inc_64(&cp->cache_alloc_fail);

        return (NULL);
}

/*
 * Destroy a slab.
 */
static void
kmem_slab_destroy(kmem_cache_t *cp, kmem_slab_t *sp)
{
        vmem_t *vmp = cp->cache_arena;
        void *slab = (void *)P2ALIGN((uintptr_t)sp->slab_base, vmp->vm_quantum);

        ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));
        ASSERT(sp->slab_refcnt == 0);

        if (cp->cache_flags & KMF_HASH) {
                kmem_bufctl_t *bcp;
                while ((bcp = sp->slab_head) != NULL) {
                        sp->slab_head = bcp->bc_next;
                        kmem_cache_free(cp->cache_bufctl_cache, bcp);
                }
                kmem_cache_free(kmem_slab_cache, sp);
        }
        vmem_free(vmp, slab, cp->cache_slabsize);
}

static void *
kmem_slab_alloc_impl(kmem_cache_t *cp, kmem_slab_t *sp, boolean_t prefill)
{
        kmem_bufctl_t *bcp, **hash_bucket;
        void *buf;
        boolean_t new_slab = (sp->slab_refcnt == 0);

        ASSERT(MUTEX_HELD(&cp->cache_lock));
        /*
         * kmem_slab_alloc() drops cache_lock when it creates a new slab, so we
         * can't ASSERT(avl_is_empty(&cp->cache_partial_slabs)) here when the
         * slab is newly created.
         */
        ASSERT(new_slab || (KMEM_SLAB_IS_PARTIAL(sp) &&
            (sp == avl_first(&cp->cache_partial_slabs))));
        ASSERT(sp->slab_cache == cp);

        cp->cache_slab_alloc++;
        cp->cache_bufslab--;
        sp->slab_refcnt++;

        bcp = sp->slab_head;
        sp->slab_head = bcp->bc_next;

        if (cp->cache_flags & KMF_HASH) {
                /*
                 * Add buffer to allocated-address hash table.
                 */
                buf = bcp->bc_addr;
                hash_bucket = KMEM_HASH(cp, buf);
                bcp->bc_next = *hash_bucket;
                *hash_bucket = bcp;
                if ((cp->cache_flags & (KMF_AUDIT | KMF_BUFTAG)) == KMF_AUDIT) {
                        KMEM_AUDIT(kmem_transaction_log, cp, bcp);
                }
        } else {
                buf = KMEM_BUF(cp, bcp);
        }

        ASSERT(KMEM_SLAB_MEMBER(sp, buf));

        if (sp->slab_head == NULL) {
                ASSERT(KMEM_SLAB_IS_ALL_USED(sp));
                if (new_slab) {
                        ASSERT(sp->slab_chunks == 1);
                } else {
                        ASSERT(sp->slab_chunks > 1); /* the slab was partial */
                        avl_remove(&cp->cache_partial_slabs, sp);
                        sp->slab_later_count = 0; /* clear history */
                        sp->slab_flags &= ~KMEM_SLAB_NOMOVE;
                        sp->slab_stuck_offset = (uint32_t)-1;
                }
                list_insert_head(&cp->cache_complete_slabs, sp);
                cp->cache_complete_slab_count++;
                return (buf);
        }

        ASSERT(KMEM_SLAB_IS_PARTIAL(sp));
        /*
         * Peek to see if the magazine layer is enabled before
         * we prefill.  We're not holding the cpu cache lock,
         * so the peek could be wrong, but there's no harm in it.
         */
        if (new_slab && prefill && (cp->cache_flags & KMF_PREFILL) &&
            (KMEM_CPU_CACHE(cp)->cc_magsize != 0))  {
                kmem_slab_prefill(cp, sp);
                return (buf);
        }

        if (new_slab) {
                avl_add(&cp->cache_partial_slabs, sp);
                return (buf);
        }

        /*
         * The slab is now more allocated than it was, so the
         * order remains unchanged.
         */
        ASSERT(!avl_update(&cp->cache_partial_slabs, sp));
        return (buf);
}

/*
 * Allocate a raw (unconstructed) buffer from cp's slab layer.
 */
static void *
kmem_slab_alloc(kmem_cache_t *cp, int kmflag)
{
        kmem_slab_t *sp;
        void *buf;
        boolean_t test_destructor;

        mutex_enter(&cp->cache_lock);
        test_destructor = (cp->cache_slab_alloc == 0);
        sp = avl_first(&cp->cache_partial_slabs);
        if (sp == NULL) {
                ASSERT(cp->cache_bufslab == 0);

                /*
                 * The freelist is empty.  Create a new slab.
                 */
                mutex_exit(&cp->cache_lock);
                if ((sp = kmem_slab_create(cp, kmflag)) == NULL) {
                        return (NULL);
                }
                mutex_enter(&cp->cache_lock);
                cp->cache_slab_create++;
                if ((cp->cache_buftotal += sp->slab_chunks) > cp->cache_bufmax)
                        cp->cache_bufmax = cp->cache_buftotal;
                cp->cache_bufslab += sp->slab_chunks;
        }

        buf = kmem_slab_alloc_impl(cp, sp, B_TRUE);
        ASSERT((cp->cache_slab_create - cp->cache_slab_destroy) ==
            (cp->cache_complete_slab_count +
            avl_numnodes(&cp->cache_partial_slabs) +
            (cp->cache_defrag == NULL ? 0 : cp->cache_defrag->kmd_deadcount)));
        mutex_exit(&cp->cache_lock);

        if (test_destructor && cp->cache_destructor != NULL) {
                /*
                 * On the first kmem_slab_alloc(), assert that it is valid to
                 * call the destructor on a newly constructed object without any
                 * client involvement.
                 */
                if ((cp->cache_constructor == NULL) ||
                    cp->cache_constructor(buf, cp->cache_private,
                    kmflag) == 0) {
                        cp->cache_destructor(buf, cp->cache_private);
                }
                copy_pattern(KMEM_UNINITIALIZED_PATTERN, buf,
                    cp->cache_bufsize);
                if (cp->cache_flags & KMF_DEADBEEF) {
                        copy_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
                }
        }

        return (buf);
}

static void kmem_slab_move_yes(kmem_cache_t *, kmem_slab_t *, void *);

/*
 * Free a raw (unconstructed) buffer to cp's slab layer.
 */
static void
kmem_slab_free(kmem_cache_t *cp, void *buf)
{
        kmem_slab_t *sp;
        kmem_bufctl_t *bcp, **prev_bcpp;

        ASSERT(buf != NULL);

        mutex_enter(&cp->cache_lock);
        cp->cache_slab_free++;

        if (cp->cache_flags & KMF_HASH) {
                /*
                 * Look up buffer in allocated-address hash table.
                 */
                prev_bcpp = KMEM_HASH(cp, buf);
                while ((bcp = *prev_bcpp) != NULL) {
                        if (bcp->bc_addr == buf) {
                                *prev_bcpp = bcp->bc_next;
                                sp = bcp->bc_slab;
                                break;
                        }
                        cp->cache_lookup_depth++;
                        prev_bcpp = &bcp->bc_next;
                }
        } else {
                bcp = KMEM_BUFCTL(cp, buf);
                sp = KMEM_SLAB(cp, buf);
        }

        if (bcp == NULL || sp->slab_cache != cp || !KMEM_SLAB_MEMBER(sp, buf)) {
                mutex_exit(&cp->cache_lock);
                kmem_error(KMERR_BADADDR, cp, buf);
                return;
        }

        if (KMEM_SLAB_OFFSET(sp, buf) == sp->slab_stuck_offset) {
                /*
                 * If this is the buffer that prevented the consolidator from
                 * clearing the slab, we can reset the slab flags now that the
                 * buffer is freed. (It makes sense to do this in
                 * kmem_cache_free(), where the client gives up ownership of the
                 * buffer, but on the hot path the test is too expensive.)
                 */
                kmem_slab_move_yes(cp, sp, buf);
        }

        if ((cp->cache_flags & (KMF_AUDIT | KMF_BUFTAG)) == KMF_AUDIT) {
                if (cp->cache_flags & KMF_CONTENTS)
                        ((kmem_bufctl_audit_t *)bcp)->bc_contents =
                            kmem_log_enter(kmem_content_log, buf,
                            cp->cache_contents);
                KMEM_AUDIT(kmem_transaction_log, cp, bcp);
        }

        bcp->bc_next = sp->slab_head;
        sp->slab_head = bcp;

        cp->cache_bufslab++;
        ASSERT(sp->slab_refcnt >= 1);

        if (--sp->slab_refcnt == 0) {
                /*
                 * There are no outstanding allocations from this slab,
                 * so we can reclaim the memory.
                 */
                if (sp->slab_chunks == 1) {
                        list_remove(&cp->cache_complete_slabs, sp);
                        cp->cache_complete_slab_count--;
                } else {
                        avl_remove(&cp->cache_partial_slabs, sp);
                }

                cp->cache_buftotal -= sp->slab_chunks;
                cp->cache_bufslab -= sp->slab_chunks;
                /*
                 * Defer releasing the slab to the virtual memory subsystem
                 * while there is a pending move callback, since we guarantee
                 * that buffers passed to the move callback have only been
                 * touched by kmem or by the client itself. Since the memory
                 * patterns baddcafe (uninitialized) and deadbeef (freed) both
                 * set at least one of the two lowest order bits, the client can
                 * test those bits in the move callback to determine whether or
                 * not it knows about the buffer (assuming that the client also
                 * sets one of those low order bits whenever it frees a buffer).
                 */
                if (cp->cache_defrag == NULL ||
                    (avl_is_empty(&cp->cache_defrag->kmd_moves_pending) &&
                    !(sp->slab_flags & KMEM_SLAB_MOVE_PENDING))) {
                        cp->cache_slab_destroy++;
                        mutex_exit(&cp->cache_lock);
                        kmem_slab_destroy(cp, sp);
                } else {
                        list_t *deadlist = &cp->cache_defrag->kmd_deadlist;
                        /*
                         * Slabs are inserted at both ends of the deadlist to
                         * distinguish between slabs freed while move callbacks
                         * are pending (list head) and a slab freed while the
                         * lock is dropped in kmem_move_buffers() (list tail) so
                         * that in both cases slab_destroy() is called from the
                         * right context.
                         */
                        if (sp->slab_flags & KMEM_SLAB_MOVE_PENDING) {
                                list_insert_tail(deadlist, sp);
                        } else {
                                list_insert_head(deadlist, sp);
                        }
                        cp->cache_defrag->kmd_deadcount++;
                        mutex_exit(&cp->cache_lock);
                }
                return;
        }

        if (bcp->bc_next == NULL) {
                /* Transition the slab from completely allocated to partial. */
                ASSERT(sp->slab_refcnt == (sp->slab_chunks - 1));
                ASSERT(sp->slab_chunks > 1);
                list_remove(&cp->cache_complete_slabs, sp);
                cp->cache_complete_slab_count--;
                avl_add(&cp->cache_partial_slabs, sp);
        } else {
                (void) avl_update_gt(&cp->cache_partial_slabs, sp);
        }

        ASSERT((cp->cache_slab_create - cp->cache_slab_destroy) ==
            (cp->cache_complete_slab_count +
            avl_numnodes(&cp->cache_partial_slabs) +
            (cp->cache_defrag == NULL ? 0 : cp->cache_defrag->kmd_deadcount)));
        mutex_exit(&cp->cache_lock);
}

/*
 * Return -1 if kmem_error, 1 if constructor fails, 0 if successful.
 */
static int
kmem_cache_alloc_debug(kmem_cache_t *cp, void *buf, int kmflag, int construct,
    caddr_t caller)
{
        kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
        kmem_bufctl_audit_t *bcp = (kmem_bufctl_audit_t *)btp->bt_bufctl;
        uint32_t mtbf;

        if (btp->bt_bxstat != ((intptr_t)bcp ^ KMEM_BUFTAG_FREE)) {
                kmem_error(KMERR_BADBUFTAG, cp, buf);
                return (-1);
        }

        btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_ALLOC;

        if ((cp->cache_flags & KMF_HASH) && bcp->bc_addr != buf) {
                kmem_error(KMERR_BADBUFCTL, cp, buf);
                return (-1);
        }

        if (cp->cache_flags & KMF_DEADBEEF) {
                if (!construct && (cp->cache_flags & KMF_LITE)) {
                        if (*(uint64_t *)buf != KMEM_FREE_PATTERN) {
                                kmem_error(KMERR_MODIFIED, cp, buf);
                                return (-1);
                        }
                        if (cp->cache_constructor != NULL)
                                *(uint64_t *)buf = btp->bt_redzone;
                        else
                                *(uint64_t *)buf = KMEM_UNINITIALIZED_PATTERN;
                } else {
                        construct = 1;
                        if (verify_and_copy_pattern(KMEM_FREE_PATTERN,
                            KMEM_UNINITIALIZED_PATTERN, buf,
                            cp->cache_verify)) {
                                kmem_error(KMERR_MODIFIED, cp, buf);
                                return (-1);
                        }
                }
        }
        btp->bt_redzone = KMEM_REDZONE_PATTERN;

        if ((mtbf = kmem_mtbf | cp->cache_mtbf) != 0 &&
            gethrtime() % mtbf == 0 &&
            (kmflag & (KM_NOSLEEP | KM_PANIC)) == KM_NOSLEEP) {
                kmem_log_event(kmem_failure_log, cp, NULL, NULL);
                if (!construct && cp->cache_destructor != NULL)
                        cp->cache_destructor(buf, cp->cache_private);
        } else {
                mtbf = 0;
        }

        if (mtbf || (construct && cp->cache_constructor != NULL &&
            cp->cache_constructor(buf, cp->cache_private, kmflag) != 0)) {
                atomic_inc_64(&cp->cache_alloc_fail);
                btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_FREE;
                if (cp->cache_flags & KMF_DEADBEEF)
                        copy_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
                kmem_slab_free(cp, buf);
                return (1);
        }

        if (cp->cache_flags & KMF_AUDIT) {
                KMEM_AUDIT(kmem_transaction_log, cp, bcp);
        }

        if ((cp->cache_flags & KMF_LITE) &&
            !(cp->cache_cflags & KMC_KMEM_ALLOC)) {
                KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count, caller);
        }

        return (0);
}

static int
kmem_cache_free_debug(kmem_cache_t *cp, void *buf, caddr_t caller)
{
        kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
        kmem_bufctl_audit_t *bcp = (kmem_bufctl_audit_t *)btp->bt_bufctl;
        kmem_slab_t *sp;

        if (btp->bt_bxstat != ((intptr_t)bcp ^ KMEM_BUFTAG_ALLOC)) {
                if (btp->bt_bxstat == ((intptr_t)bcp ^ KMEM_BUFTAG_FREE)) {
                        kmem_error(KMERR_DUPFREE, cp, buf);
                        return (-1);
                }
                sp = kmem_findslab(cp, buf);
                if (sp == NULL || sp->slab_cache != cp)
                        kmem_error(KMERR_BADADDR, cp, buf);
                else
                        kmem_error(KMERR_REDZONE, cp, buf);
                return (-1);
        }

        btp->bt_bxstat = (intptr_t)bcp ^ KMEM_BUFTAG_FREE;

        if ((cp->cache_flags & KMF_HASH) && bcp->bc_addr != buf) {
                kmem_error(KMERR_BADBUFCTL, cp, buf);
                return (-1);
        }

        if (btp->bt_redzone != KMEM_REDZONE_PATTERN) {
                kmem_error(KMERR_REDZONE, cp, buf);
                return (-1);
        }

        if (cp->cache_flags & KMF_AUDIT) {
                if (cp->cache_flags & KMF_CONTENTS)
                        bcp->bc_contents = kmem_log_enter(kmem_content_log,
                            buf, cp->cache_contents);
                KMEM_AUDIT(kmem_transaction_log, cp, bcp);
        }

        if ((cp->cache_flags & KMF_LITE) &&
            !(cp->cache_cflags & KMC_KMEM_ALLOC)) {
                KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count, caller);
        }

        if (cp->cache_flags & KMF_DEADBEEF) {
                if (cp->cache_flags & KMF_LITE)
                        btp->bt_redzone = *(uint64_t *)buf;
                else if (cp->cache_destructor != NULL)
                        cp->cache_destructor(buf, cp->cache_private);

                copy_pattern(KMEM_FREE_PATTERN, buf, cp->cache_verify);
        }

        return (0);
}

/*
 * Free each object in magazine mp to cp's slab layer, and free mp itself.
 */
static void
kmem_magazine_destroy(kmem_cache_t *cp, kmem_magazine_t *mp, int nrounds)
{
        int round;

        ASSERT(!list_link_active(&cp->cache_link) ||
            taskq_member(kmem_taskq, curthread));

        for (round = 0; round < nrounds; round++) {
                void *buf = mp->mag_round[round];

                if (cp->cache_flags & KMF_DEADBEEF) {
                        if (verify_pattern(KMEM_FREE_PATTERN, buf,
                            cp->cache_verify) != NULL) {
                                kmem_error(KMERR_MODIFIED, cp, buf);
                                continue;
                        }
                        if ((cp->cache_flags & KMF_LITE) &&
                            cp->cache_destructor != NULL) {
                                kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
                                *(uint64_t *)buf = btp->bt_redzone;
                                cp->cache_destructor(buf, cp->cache_private);
                                *(uint64_t *)buf = KMEM_FREE_PATTERN;
                        }
                } else if (cp->cache_destructor != NULL) {
                        cp->cache_destructor(buf, cp->cache_private);
                }

                kmem_slab_free(cp, buf);
        }
        ASSERT(KMEM_MAGAZINE_VALID(cp, mp));
        kmem_cache_free(cp->cache_magtype->mt_cache, mp);
}

/*
 * Allocate a magazine from the depot.
 */
static kmem_magazine_t *
kmem_depot_alloc(kmem_cache_t *cp, kmem_maglist_t *mlp)
{
        kmem_magazine_t *mp;

        /*
         * If we can't get the depot lock without contention,
         * update our contention count.  We use the depot
         * contention rate to determine whether we need to
         * increase the magazine size for better scalability.
         */
        if (!mutex_tryenter(&cp->cache_depot_lock)) {
                mutex_enter(&cp->cache_depot_lock);
                cp->cache_depot_contention++;
        }

        if ((mp = mlp->ml_list) != NULL) {
                ASSERT(KMEM_MAGAZINE_VALID(cp, mp));
                mlp->ml_list = mp->mag_next;
                if (--mlp->ml_total < mlp->ml_min)
                        mlp->ml_min = mlp->ml_total;
                mlp->ml_alloc++;
        }

        mutex_exit(&cp->cache_depot_lock);

        return (mp);
}

/*
 * Free a magazine to the depot.
 */
static void
kmem_depot_free(kmem_cache_t *cp, kmem_maglist_t *mlp, kmem_magazine_t *mp)
{
        mutex_enter(&cp->cache_depot_lock);
        ASSERT(KMEM_MAGAZINE_VALID(cp, mp));
        mp->mag_next = mlp->ml_list;
        mlp->ml_list = mp;
        mlp->ml_total++;
        mutex_exit(&cp->cache_depot_lock);
}

/*
 * Update the working set statistics for cp's depot.
 */
static void
kmem_depot_ws_update(kmem_cache_t *cp)
{
        mutex_enter(&cp->cache_depot_lock);
        cp->cache_full.ml_reaplimit = cp->cache_full.ml_min;
        cp->cache_full.ml_min = cp->cache_full.ml_total;
        cp->cache_empty.ml_reaplimit = cp->cache_empty.ml_min;
        cp->cache_empty.ml_min = cp->cache_empty.ml_total;
        mutex_exit(&cp->cache_depot_lock);
}

/*
 * Set the working set statistics for cp's depot to zero.  (Everything is
 * eligible for reaping.)
 */
static void
kmem_depot_ws_zero(kmem_cache_t *cp)
{
        mutex_enter(&cp->cache_depot_lock);
        cp->cache_full.ml_reaplimit = cp->cache_full.ml_total;
        cp->cache_full.ml_min = cp->cache_full.ml_total;
        cp->cache_empty.ml_reaplimit = cp->cache_empty.ml_total;
        cp->cache_empty.ml_min = cp->cache_empty.ml_total;
        mutex_exit(&cp->cache_depot_lock);
}

/*
 * The number of bytes to reap before we call kpreempt(). The default (1MB)
 * causes us to preempt reaping up to hundreds of times per second. Using a
 * larger value (1GB) causes this to have virtually no effect.
 */
size_t kmem_reap_preempt_bytes = 1024 * 1024;

/*
 * Reap all magazines that have fallen out of the depot's working set.
 */
static void
kmem_depot_ws_reap(kmem_cache_t *cp)
{
        size_t bytes = 0;
        long reap;
        kmem_magazine_t *mp;

        ASSERT(!list_link_active(&cp->cache_link) ||
            taskq_member(kmem_taskq, curthread));

        reap = MIN(cp->cache_full.ml_reaplimit, cp->cache_full.ml_min);
        while (reap-- &&
            (mp = kmem_depot_alloc(cp, &cp->cache_full)) != NULL) {
                kmem_magazine_destroy(cp, mp, cp->cache_magtype->mt_magsize);
                bytes += cp->cache_magtype->mt_magsize * cp->cache_bufsize;
                if (bytes > kmem_reap_preempt_bytes) {
                        kpreempt(KPREEMPT_SYNC);
                        bytes = 0;
                }
        }

        reap = MIN(cp->cache_empty.ml_reaplimit, cp->cache_empty.ml_min);
        while (reap-- &&
            (mp = kmem_depot_alloc(cp, &cp->cache_empty)) != NULL) {
                kmem_magazine_destroy(cp, mp, 0);
                bytes += cp->cache_magtype->mt_magsize * cp->cache_bufsize;
                if (bytes > kmem_reap_preempt_bytes) {
                        kpreempt(KPREEMPT_SYNC);
                        bytes = 0;
                }
        }
}

static void
kmem_cpu_reload(kmem_cpu_cache_t *ccp, kmem_magazine_t *mp, int rounds)
{
        ASSERT((ccp->cc_loaded == NULL && ccp->cc_rounds == -1) ||
            (ccp->cc_loaded && ccp->cc_rounds + rounds == ccp->cc_magsize));
        ASSERT(ccp->cc_magsize > 0);

        ccp->cc_ploaded = ccp->cc_loaded;
        ccp->cc_prounds = ccp->cc_rounds;
        ccp->cc_loaded = mp;
        ccp->cc_rounds = rounds;
}

/*
 * Intercept kmem alloc/free calls during crash dump in order to avoid
 * changing kmem state while memory is being saved to the dump device.
 * Otherwise, ::kmem_verify will report "corrupt buffers".  Note that
 * there are no locks because only one CPU calls kmem during a crash
 * dump. To enable this feature, first create the associated vmem
 * arena with VMC_DUMPSAFE.
 */
static void *kmem_dump_start;   /* start of pre-reserved heap */
static void *kmem_dump_end;     /* end of heap area */
static void *kmem_dump_curr;    /* current free heap pointer */
static size_t kmem_dump_size;   /* size of heap area */

/* append to each buf created in the pre-reserved heap */
typedef struct kmem_dumpctl {
        void    *kdc_next;      /* cache dump free list linkage */
} kmem_dumpctl_t;

#define KMEM_DUMPCTL(cp, buf)   \
        ((kmem_dumpctl_t *)P2ROUNDUP((uintptr_t)(buf) + (cp)->cache_bufsize, \
            sizeof (void *)))

/* Keep some simple stats. */
#define KMEM_DUMP_LOGS  (100)

typedef struct kmem_dump_log {
        kmem_cache_t    *kdl_cache;
        uint_t          kdl_allocs;             /* # of dump allocations */
        uint_t          kdl_frees;              /* # of dump frees */
        uint_t          kdl_alloc_fails;        /* # of allocation failures */
        uint_t          kdl_free_nondump;       /* # of non-dump frees */
        uint_t          kdl_unsafe;             /* cache was used, but unsafe */
} kmem_dump_log_t;

static kmem_dump_log_t *kmem_dump_log;
static int kmem_dump_log_idx;

#define KDI_LOG(cp, stat) {                                             \
        kmem_dump_log_t *kdl;                                           \
        if ((kdl = (kmem_dump_log_t *)((cp)->cache_dumplog)) != NULL) { \
                kdl->stat++;                                            \
        } else if (kmem_dump_log_idx < KMEM_DUMP_LOGS) {                \
                kdl = &kmem_dump_log[kmem_dump_log_idx++];              \
                kdl->stat++;                                            \
                kdl->kdl_cache = (cp);                                  \
                (cp)->cache_dumplog = kdl;                              \
        }                                                               \
}

/* set non zero for full report */
uint_t kmem_dump_verbose = 0;

/* stats for overize heap */
uint_t kmem_dump_oversize_allocs = 0;
uint_t kmem_dump_oversize_max = 0;

static void
kmem_dumppr(char **pp, char *e, const char *format, ...)
{
        char *p = *pp;

        if (p < e) {
                int n;
                va_list ap;

                va_start(ap, format);
                n = vsnprintf(p, e - p, format, ap);
                va_end(ap);
                *pp = p + n;
        }
}

/*
 * Called when dumpadm(1M) configures dump parameters.
 */
void
kmem_dump_init(size_t size)
{
        if (kmem_dump_start != NULL)
                kmem_free(kmem_dump_start, kmem_dump_size);

        if (kmem_dump_log == NULL)
                kmem_dump_log = (kmem_dump_log_t *)kmem_zalloc(KMEM_DUMP_LOGS *
                    sizeof (kmem_dump_log_t), KM_SLEEP);

        kmem_dump_start = kmem_alloc(size, KM_SLEEP);

        if (kmem_dump_start != NULL) {
                kmem_dump_size = size;
                kmem_dump_curr = kmem_dump_start;
                kmem_dump_end = (void *)((char *)kmem_dump_start + size);
                copy_pattern(KMEM_UNINITIALIZED_PATTERN, kmem_dump_start, size);
        } else {
                kmem_dump_size = 0;
                kmem_dump_curr = NULL;
                kmem_dump_end = NULL;
        }
}

/*
 * Set flag for each kmem_cache_t if is safe to use alternate dump
 * memory. Called just before panic crash dump starts. Set the flag
 * for the calling CPU.
 */
void
kmem_dump_begin(void)
{
        ASSERT(panicstr != NULL);
        if (kmem_dump_start != NULL) {
                kmem_cache_t *cp;

                for (cp = list_head(&kmem_caches); cp != NULL;
                    cp = list_next(&kmem_caches, cp)) {
                        kmem_cpu_cache_t *ccp = KMEM_CPU_CACHE(cp);

                        if (cp->cache_arena->vm_cflags & VMC_DUMPSAFE) {
                                cp->cache_flags |= KMF_DUMPDIVERT;
                                ccp->cc_flags |= KMF_DUMPDIVERT;
                                ccp->cc_dump_rounds = ccp->cc_rounds;
                                ccp->cc_dump_prounds = ccp->cc_prounds;
                                ccp->cc_rounds = ccp->cc_prounds = -1;
                        } else {
                                cp->cache_flags |= KMF_DUMPUNSAFE;
                                ccp->cc_flags |= KMF_DUMPUNSAFE;
                        }
                }
        }
}

/*
 * finished dump intercept
 * print any warnings on the console
 * return verbose information to dumpsys() in the given buffer
 */
size_t
kmem_dump_finish(char *buf, size_t size)
{
        int kdi_idx;
        int kdi_end = kmem_dump_log_idx;
        int percent = 0;
        int header = 0;
        int warn = 0;
        size_t used;
        kmem_cache_t *cp;
        kmem_dump_log_t *kdl;
        char *e = buf + size;
        char *p = buf;

        if (kmem_dump_size == 0 || kmem_dump_verbose == 0)
                return (0);

        used = (char *)kmem_dump_curr - (char *)kmem_dump_start;
        percent = (used * 100) / kmem_dump_size;

        kmem_dumppr(&p, e, "%% heap used,%d\n", percent);
        kmem_dumppr(&p, e, "used bytes,%ld\n", used);
        kmem_dumppr(&p, e, "heap size,%ld\n", kmem_dump_size);
        kmem_dumppr(&p, e, "Oversize allocs,%d\n",
            kmem_dump_oversize_allocs);
        kmem_dumppr(&p, e, "Oversize max size,%ld\n",
            kmem_dump_oversize_max);

        for (kdi_idx = 0; kdi_idx < kdi_end; kdi_idx++) {
                kdl = &kmem_dump_log[kdi_idx];
                cp = kdl->kdl_cache;
                if (cp == NULL)
                        break;
                if (kdl->kdl_alloc_fails)
                        ++warn;
                if (header == 0) {
                        kmem_dumppr(&p, e,
                            "Cache Name,Allocs,Frees,Alloc Fails,"
                            "Nondump Frees,Unsafe Allocs/Frees\n");
                        header = 1;
                }
                kmem_dumppr(&p, e, "%s,%d,%d,%d,%d,%d\n",
                    cp->cache_name, kdl->kdl_allocs, kdl->kdl_frees,
                    kdl->kdl_alloc_fails, kdl->kdl_free_nondump,
                    kdl->kdl_unsafe);
        }

        /* return buffer size used */
        if (p < e)
                bzero(p, e - p);
        return (p - buf);
}

/*
 * Allocate a constructed object from alternate dump memory.
 */
void *
kmem_cache_alloc_dump(kmem_cache_t *cp, int kmflag)
{
        void *buf;
        void *curr;
        char *bufend;

        /* return a constructed object */
        if ((buf = cp->cache_dumpfreelist) != NULL) {
                cp->cache_dumpfreelist = KMEM_DUMPCTL(cp, buf)->kdc_next;
                KDI_LOG(cp, kdl_allocs);
                return (buf);
        }

        /* create a new constructed object */
        curr = kmem_dump_curr;
        buf = (void *)P2ROUNDUP((uintptr_t)curr, cp->cache_align);
        bufend = (char *)KMEM_DUMPCTL(cp, buf) + sizeof (kmem_dumpctl_t);

        /* hat layer objects cannot cross a page boundary */
        if (cp->cache_align < PAGESIZE) {
                char *page = (char *)P2ROUNDUP((uintptr_t)buf, PAGESIZE);
                if (bufend > page) {
                        bufend += page - (char *)buf;
                        buf = (void *)page;
                }
        }

        /* fall back to normal alloc if reserved area is used up */
        if (bufend > (char *)kmem_dump_end) {
                kmem_dump_curr = kmem_dump_end;
                KDI_LOG(cp, kdl_alloc_fails);
                return (NULL);
        }

        /*
         * Must advance curr pointer before calling a constructor that
         * may also allocate memory.
         */
        kmem_dump_curr = bufend;

        /* run constructor */
        if (cp->cache_constructor != NULL &&
            cp->cache_constructor(buf, cp->cache_private, kmflag)
            != 0) {
#ifdef DEBUG
                printf("name='%s' cache=0x%p: kmem cache constructor failed\n",
                    cp->cache_name, (void *)cp);
#endif
                /* reset curr pointer iff no allocs were done */
                if (kmem_dump_curr == bufend)
                        kmem_dump_curr = curr;

                /* fall back to normal alloc if the constructor fails */
                KDI_LOG(cp, kdl_alloc_fails);
                return (NULL);
        }

        KDI_LOG(cp, kdl_allocs);
        return (buf);
}

/*
 * Free a constructed object in alternate dump memory.
 */
int
kmem_cache_free_dump(kmem_cache_t *cp, void *buf)
{
        /* save constructed buffers for next time */
        if ((char *)buf >= (char *)kmem_dump_start &&
            (char *)buf < (char *)kmem_dump_end) {
                KMEM_DUMPCTL(cp, buf)->kdc_next = cp->cache_dumpfreelist;
                cp->cache_dumpfreelist = buf;
                KDI_LOG(cp, kdl_frees);
                return (0);
        }

        /* count all non-dump buf frees */
        KDI_LOG(cp, kdl_free_nondump);

        /* just drop buffers that were allocated before dump started */
        if (kmem_dump_curr < kmem_dump_end)
                return (0);

        /* fall back to normal free if reserved area is used up */
        return (1);
}

/*
 * Allocate a constructed object from cache cp.
 */
void *
kmem_cache_alloc(kmem_cache_t *cp, int kmflag)
{
        kmem_cpu_cache_t *ccp = KMEM_CPU_CACHE(cp);
        kmem_magazine_t *fmp;
        void *buf;

        mutex_enter(&ccp->cc_lock);
        for (;;) {
                /*
                 * If there's an object available in the current CPU's
                 * loaded magazine, just take it and return.
                 */
                if (ccp->cc_rounds > 0) {
                        buf = ccp->cc_loaded->mag_round[--ccp->cc_rounds];
                        ccp->cc_alloc++;
                        mutex_exit(&ccp->cc_lock);
                        if (ccp->cc_flags & (KMF_BUFTAG | KMF_DUMPUNSAFE)) {
                                if (ccp->cc_flags & KMF_DUMPUNSAFE) {
                                        ASSERT(!(ccp->cc_flags &
                                            KMF_DUMPDIVERT));
                                        KDI_LOG(cp, kdl_unsafe);
                                }
                                if ((ccp->cc_flags & KMF_BUFTAG) &&
                                    kmem_cache_alloc_debug(cp, buf, kmflag, 0,
                                    caller()) != 0) {
                                        if (kmflag & KM_NOSLEEP)
                                                return (NULL);
                                        mutex_enter(&ccp->cc_lock);
                                        continue;
                                }
                        }
                        goto done;
                }

                /*
                 * The loaded magazine is empty.  If the previously loaded
                 * magazine was full, exchange them and try again.
                 */
                if (ccp->cc_prounds > 0) {
                        kmem_cpu_reload(ccp, ccp->cc_ploaded, ccp->cc_prounds);
                        continue;
                }

                /*
                 * Return an alternate buffer at dump time to preserve
                 * the heap.
                 */
                if (ccp->cc_flags & (KMF_DUMPDIVERT | KMF_DUMPUNSAFE)) {
                        if (ccp->cc_flags & KMF_DUMPUNSAFE) {
                                ASSERT(!(ccp->cc_flags & KMF_DUMPDIVERT));
                                /* log it so that we can warn about it */
                                KDI_LOG(cp, kdl_unsafe);
                        } else {
                                if ((buf = kmem_cache_alloc_dump(cp, kmflag)) !=
                                    NULL) {
                                        mutex_exit(&ccp->cc_lock);
                                        goto done;
                                }
                                break;          /* fall back to slab layer */
                        }
                }

                /*
                 * If the magazine layer is disabled, break out now.
                 */
                if (ccp->cc_magsize == 0)
                        break;

                /*
                 * Try to get a full magazine from the depot.
                 */
                fmp = kmem_depot_alloc(cp, &cp->cache_full);
                if (fmp != NULL) {
                        if (ccp->cc_ploaded != NULL)
                                kmem_depot_free(cp, &cp->cache_empty,
                                    ccp->cc_ploaded);
                        kmem_cpu_reload(ccp, fmp, ccp->cc_magsize);
                        continue;
                }

                /*
                 * There are no full magazines in the depot,
                 * so fall through to the slab layer.
                 */
                break;
        }
        mutex_exit(&ccp->cc_lock);

        /*
         * We couldn't allocate a constructed object from the magazine layer,
         * so get a raw buffer from the slab layer and apply its constructor.
         */
        buf = kmem_slab_alloc(cp, kmflag);

        if (buf == NULL)
                return (NULL);

        if (cp->cache_flags & KMF_BUFTAG) {
                /*
                 * Make kmem_cache_alloc_debug() apply the constructor for us.
                 */
                int rc = kmem_cache_alloc_debug(cp, buf, kmflag, 1, caller());
                if (rc != 0) {
                        if (kmflag & KM_NOSLEEP)
                                return (NULL);
                        /*
                         * kmem_cache_alloc_debug() detected corruption
                         * but didn't panic (kmem_panic <= 0). We should not be
                         * here because the constructor failed (indicated by a
                         * return code of 1). Try again.
                         */
                        ASSERT(rc == -1);
                        return (kmem_cache_alloc(cp, kmflag));
                }
                goto done;
        }

        if (cp->cache_constructor != NULL &&
            cp->cache_constructor(buf, cp->cache_private, kmflag) != 0) {
                atomic_inc_64(&cp->cache_alloc_fail);
                kmem_slab_free(cp, buf);
                return (NULL);
        }

done:
        if (buf != NULL && (kmflag & KM_ZERO))
                bzero(buf, cp->cache_bufsize);

        return (buf);
}

/*
 * The freed argument tells whether or not kmem_cache_free_debug() has already
 * been called so that we can avoid the duplicate free error. For example, a
 * buffer on a magazine has already been freed by the client but is still
 * constructed.
 */
static void
kmem_slab_free_constructed(kmem_cache_t *cp, void *buf, boolean_t freed)
{
        if (!freed && (cp->cache_flags & KMF_BUFTAG))
                if (kmem_cache_free_debug(cp, buf, caller()) == -1)
                        return;

        /*
         * Note that if KMF_DEADBEEF is in effect and KMF_LITE is not,
         * kmem_cache_free_debug() will have already applied the destructor.
         */
        if ((cp->cache_flags & (KMF_DEADBEEF | KMF_LITE)) != KMF_DEADBEEF &&
            cp->cache_destructor != NULL) {
                if (cp->cache_flags & KMF_DEADBEEF) {   /* KMF_LITE implied */
                        kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
                        *(uint64_t *)buf = btp->bt_redzone;
                        cp->cache_destructor(buf, cp->cache_private);
                        *(uint64_t *)buf = KMEM_FREE_PATTERN;
                } else {
                        cp->cache_destructor(buf, cp->cache_private);
                }
        }

        kmem_slab_free(cp, buf);
}

/*
 * Used when there's no room to free a buffer to the per-CPU cache.
 * Drops and re-acquires &ccp->cc_lock, and returns non-zero if the
 * caller should try freeing to the per-CPU cache again.
 * Note that we don't directly install the magazine in the cpu cache,
 * since its state may have changed wildly while the lock was dropped.
 */
static int
kmem_cpucache_magazine_alloc(kmem_cpu_cache_t *ccp, kmem_cache_t *cp)
{
        kmem_magazine_t *emp;
        kmem_magtype_t *mtp;

        ASSERT(MUTEX_HELD(&ccp->cc_lock));
        ASSERT(((uint_t)ccp->cc_rounds == ccp->cc_magsize ||
            ((uint_t)ccp->cc_rounds == -1)) &&
            ((uint_t)ccp->cc_prounds == ccp->cc_magsize ||
            ((uint_t)ccp->cc_prounds == -1)));

        emp = kmem_depot_alloc(cp, &cp->cache_empty);
        if (emp != NULL) {
                if (ccp->cc_ploaded != NULL)
                        kmem_depot_free(cp, &cp->cache_full,
                            ccp->cc_ploaded);
                kmem_cpu_reload(ccp, emp, 0);
                return (1);
        }
        /*
         * There are no empty magazines in the depot,
         * so try to allocate a new one.  We must drop all locks
         * across kmem_cache_alloc() because lower layers may
         * attempt to allocate from this cache.
         */
        mtp = cp->cache_magtype;
        mutex_exit(&ccp->cc_lock);
        emp = kmem_cache_alloc(mtp->mt_cache, KM_NOSLEEP);
        mutex_enter(&ccp->cc_lock);

        if (emp != NULL) {
                /*
                 * We successfully allocated an empty magazine.
                 * However, we had to drop ccp->cc_lock to do it,
                 * so the cache's magazine size may have changed.
                 * If so, free the magazine and try again.
                 */
                if (ccp->cc_magsize != mtp->mt_magsize) {
                        mutex_exit(&ccp->cc_lock);
                        kmem_cache_free(mtp->mt_cache, emp);
                        mutex_enter(&ccp->cc_lock);
                        return (1);
                }

                /*
                 * We got a magazine of the right size.  Add it to
                 * the depot and try the whole dance again.
                 */
                kmem_depot_free(cp, &cp->cache_empty, emp);
                return (1);
        }

        /*
         * We couldn't allocate an empty magazine,
         * so fall through to the slab layer.
         */
        return (0);
}

/*
 * Free a constructed object to cache cp.
 */
void
kmem_cache_free(kmem_cache_t *cp, void *buf)
{
        kmem_cpu_cache_t *ccp = KMEM_CPU_CACHE(cp);

        /*
         * The client must not free either of the buffers passed to the move
         * callback function.
         */
        ASSERT(cp->cache_defrag == NULL ||
            cp->cache_defrag->kmd_thread != curthread ||
            (buf != cp->cache_defrag->kmd_from_buf &&
            buf != cp->cache_defrag->kmd_to_buf));

        if (ccp->cc_flags & (KMF_BUFTAG | KMF_DUMPDIVERT | KMF_DUMPUNSAFE)) {
                if (ccp->cc_flags & KMF_DUMPUNSAFE) {
                        ASSERT(!(ccp->cc_flags & KMF_DUMPDIVERT));
                        /* log it so that we can warn about it */
                        KDI_LOG(cp, kdl_unsafe);
                } else if (KMEM_DUMPCC(ccp) && !kmem_cache_free_dump(cp, buf)) {
                        return;
                }
                if (ccp->cc_flags & KMF_BUFTAG) {
                        if (kmem_cache_free_debug(cp, buf, caller()) == -1)
                                return;
                }
        }

        mutex_enter(&ccp->cc_lock);
        /*
         * Any changes to this logic should be reflected in kmem_slab_prefill()
         */
        for (;;) {
                /*
                 * If there's a slot available in the current CPU's
                 * loaded magazine, just put the object there and return.
                 */
                if ((uint_t)ccp->cc_rounds < ccp->cc_magsize) {
                        ccp->cc_loaded->mag_round[ccp->cc_rounds++] = buf;
                        ccp->cc_free++;
                        mutex_exit(&ccp->cc_lock);
                        return;
                }

                /*
                 * The loaded magazine is full.  If the previously loaded
                 * magazine was empty, exchange them and try again.
                 */
                if (ccp->cc_prounds == 0) {
                        kmem_cpu_reload(ccp, ccp->cc_ploaded, ccp->cc_prounds);
                        continue;
                }

                /*
                 * If the magazine layer is disabled, break out now.
                 */
                if (ccp->cc_magsize == 0)
                        break;

                if (!kmem_cpucache_magazine_alloc(ccp, cp)) {
                        /*
                         * We couldn't free our constructed object to the
                         * magazine layer, so apply its destructor and free it
                         * to the slab layer.
                         */
                        break;
                }
        }
        mutex_exit(&ccp->cc_lock);
        kmem_slab_free_constructed(cp, buf, B_TRUE);
}

static void
kmem_slab_prefill(kmem_cache_t *cp, kmem_slab_t *sp)
{
        kmem_cpu_cache_t *ccp = KMEM_CPU_CACHE(cp);
        int cache_flags = cp->cache_flags;

        kmem_bufctl_t *next, *head;
        size_t nbufs;

        /*
         * Completely allocate the newly created slab and put the pre-allocated
         * buffers in magazines. Any of the buffers that cannot be put in
         * magazines must be returned to the slab.
         */
        ASSERT(MUTEX_HELD(&cp->cache_lock));
        ASSERT((cache_flags & (KMF_PREFILL|KMF_BUFTAG)) == KMF_PREFILL);
        ASSERT(cp->cache_constructor == NULL);
        ASSERT(sp->slab_cache == cp);
        ASSERT(sp->slab_refcnt == 1);
        ASSERT(sp->slab_head != NULL && sp->slab_chunks > sp->slab_refcnt);
        ASSERT(avl_find(&cp->cache_partial_slabs, sp, NULL) == NULL);

        head = sp->slab_head;
        nbufs = (sp->slab_chunks - sp->slab_refcnt);
        sp->slab_head = NULL;
        sp->slab_refcnt += nbufs;
        cp->cache_bufslab -= nbufs;
        cp->cache_slab_alloc += nbufs;
        list_insert_head(&cp->cache_complete_slabs, sp);
        cp->cache_complete_slab_count++;
        mutex_exit(&cp->cache_lock);
        mutex_enter(&ccp->cc_lock);

        while (head != NULL) {
                void *buf = KMEM_BUF(cp, head);
                /*
                 * If there's a slot available in the current CPU's
                 * loaded magazine, just put the object there and
                 * continue.
                 */
                if ((uint_t)ccp->cc_rounds < ccp->cc_magsize) {
                        ccp->cc_loaded->mag_round[ccp->cc_rounds++] =
                            buf;
                        ccp->cc_free++;
                        nbufs--;
                        head = head->bc_next;
                        continue;
                }

                /*
                 * The loaded magazine is full.  If the previously
                 * loaded magazine was empty, exchange them and try
                 * again.
                 */
                if (ccp->cc_prounds == 0) {
                        kmem_cpu_reload(ccp, ccp->cc_ploaded,
                            ccp->cc_prounds);
                        continue;
                }

                /*
                 * If the magazine layer is disabled, break out now.
                 */

                if (ccp->cc_magsize == 0) {
                        break;
                }

                if (!kmem_cpucache_magazine_alloc(ccp, cp))
                        break;
        }
        mutex_exit(&ccp->cc_lock);
        if (nbufs != 0) {
                ASSERT(head != NULL);

                /*
                 * If there was a failure, return remaining objects to
                 * the slab
                 */
                while (head != NULL) {
                        ASSERT(nbufs != 0);
                        next = head->bc_next;
                        head->bc_next = NULL;
                        kmem_slab_free(cp, KMEM_BUF(cp, head));
                        head = next;
                        nbufs--;
                }
        }
        ASSERT(head == NULL);
        ASSERT(nbufs == 0);
        mutex_enter(&cp->cache_lock);
}

static void *
do_kmem_alloc(size_t size, int kmflag, void *caller_pc)
{
        size_t index;
        kmem_cache_t *cp;
        void *buf;

        if ((index = ((size - 1) >> KMEM_ALIGN_SHIFT)) < KMEM_ALLOC_TABLE_MAX) {
                cp = kmem_alloc_table[index];
                /* fall through to kmem_cache_alloc() */

        } else if ((index = ((size - 1) >> KMEM_BIG_SHIFT)) <
            kmem_big_alloc_table_max) {
                cp = kmem_big_alloc_table[index];
                /* fall through to kmem_cache_alloc() */

        } else {
                if (size == 0)
                        return (NULL);

                buf = vmem_alloc(kmem_oversize_arena, size,
                    kmflag & KM_VMFLAGS);
                if (buf == NULL)
                        kmem_log_event(kmem_failure_log, NULL, NULL,
                            (void *)size);
                else if (KMEM_DUMP(kmem_slab_cache)) {
                        /* stats for dump intercept */
                        kmem_dump_oversize_allocs++;
                        if (size > kmem_dump_oversize_max)
                                kmem_dump_oversize_max = size;
                }
                if (buf != NULL && (kmflag & KM_ZERO))
                        bzero(buf, size);
                return (buf);
        }

        buf = kmem_cache_alloc(cp, kmflag);
        if ((cp->cache_flags & KMF_BUFTAG) && !KMEM_DUMP(cp) && buf != NULL) {
                kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
                ((uint8_t *)buf)[size] = KMEM_REDZONE_BYTE;
                ((uint32_t *)btp)[1] = KMEM_SIZE_ENCODE(size);

                if (cp->cache_flags & KMF_LITE) {
                        KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count, caller_pc);
                }
        }
        return (buf);
}

void *
kmem_zalloc(size_t size, int kmflag)
{
        return (do_kmem_alloc(size, kmflag | KM_ZERO, caller()));
}

void *
kmem_alloc(size_t size, int kmflag)
{
        return (do_kmem_alloc(size, kmflag, caller()));
}

void
kmem_free(void *buf, size_t size)
{
        size_t index;
        kmem_cache_t *cp;

        if ((index = (size - 1) >> KMEM_ALIGN_SHIFT) < KMEM_ALLOC_TABLE_MAX) {
                cp = kmem_alloc_table[index];
                /* fall through to kmem_cache_free() */

        } else if ((index = ((size - 1) >> KMEM_BIG_SHIFT)) <
            kmem_big_alloc_table_max) {
                cp = kmem_big_alloc_table[index];
                /* fall through to kmem_cache_free() */

        } else {
                EQUIV(buf == NULL, size == 0);
                if (buf == NULL && size == 0)
                        return;
                vmem_free(kmem_oversize_arena, buf, size);
                return;
        }

        if ((cp->cache_flags & KMF_BUFTAG) && !KMEM_DUMP(cp)) {
                kmem_buftag_t *btp = KMEM_BUFTAG(cp, buf);
                uint32_t *ip = (uint32_t *)btp;
                if (ip[1] != KMEM_SIZE_ENCODE(size)) {
                        if (*(uint64_t *)buf == KMEM_FREE_PATTERN) {
                                kmem_error(KMERR_DUPFREE, cp, buf);
                                return;
                        }
                        if (KMEM_SIZE_VALID(ip[1])) {
                                ip[0] = KMEM_SIZE_ENCODE(size);
                                kmem_error(KMERR_BADSIZE, cp, buf);
                        } else {
                                kmem_error(KMERR_REDZONE, cp, buf);
                        }
                        return;
                }
                if (((uint8_t *)buf)[size] != KMEM_REDZONE_BYTE) {
                        kmem_error(KMERR_REDZONE, cp, buf);
                        return;
                }
                btp->bt_redzone = KMEM_REDZONE_PATTERN;
                if (cp->cache_flags & KMF_LITE) {
                        KMEM_BUFTAG_LITE_ENTER(btp, kmem_lite_count,
                            caller());
                }
        }
        kmem_cache_free(cp, buf);
}

void *
kmem_firewall_va_alloc(vmem_t *vmp, size_t size, int vmflag)
{
        size_t realsize = size + vmp->vm_quantum;
        void *addr;

        /*
         * Annoying edge case: if 'size' is just shy of ULONG_MAX, adding
         * vm_quantum will cause integer wraparound.  Check for this, and
         * blow off the firewall page in this case.  Note that such a
         * giant allocation (the entire kernel address space) can never
         * be satisfied, so it will either fail immediately (VM_NOSLEEP)
         * or sleep forever (VM_SLEEP).  Thus, there is no need for a
         * corresponding check in kmem_firewall_va_free().
         */
        if (realsize < size)
                realsize = size;

        /*
         * While boot still owns resource management, make sure that this
         * redzone virtual address allocation is properly accounted for in
         * OBPs "virtual-memory" "available" lists because we're
         * effectively claiming them for a red zone.  If we don't do this,
         * the available lists become too fragmented and too large for the
         * current boot/kernel memory list interface.
         */
        addr = vmem_alloc(vmp, realsize, vmflag | VM_NEXTFIT);

        if (addr != NULL && kvseg.s_base == NULL && realsize != size)
                (void) boot_virt_alloc((char *)addr + size, vmp->vm_quantum);

        return (addr);
}

void
kmem_firewall_va_free(vmem_t *vmp, void *addr, size_t size)
{
        ASSERT((kvseg.s_base == NULL ?
            va_to_pfn((char *)addr + size) :
            hat_getpfnum(kas.a_hat, (caddr_t)addr + size)) == PFN_INVALID);

        vmem_free(vmp, addr, size + vmp->vm_quantum);
}

/*
 * Try to allocate at least `size' bytes of memory without sleeping or
 * panicking. Return actual allocated size in `asize'. If allocation failed,
 * try final allocation with sleep or panic allowed.
 */
void *
kmem_alloc_tryhard(size_t size, size_t *asize, int kmflag)
{
        void *p;

        *asize = P2ROUNDUP(size, KMEM_ALIGN);
        do {
                p = kmem_alloc(*asize, (kmflag | KM_NOSLEEP) & ~KM_PANIC);
                if (p != NULL)
                        return (p);
                *asize += KMEM_ALIGN;
        } while (*asize <= PAGESIZE);

        *asize = P2ROUNDUP(size, KMEM_ALIGN);
        return (kmem_alloc(*asize, kmflag));
}

/*
 * Reclaim all unused memory from a cache.
 */
static void
kmem_cache_reap(kmem_cache_t *cp)
{
        ASSERT(taskq_member(kmem_taskq, curthread));
        cp->cache_reap++;

        /*
         * Ask the cache's owner to free some memory if possible.
         * The idea is to handle things like the inode cache, which
         * typically sits on a bunch of memory that it doesn't truly
         * *need*.  Reclaim policy is entirely up to the owner; this
         * callback is just an advisory plea for help.
         */
        if (cp->cache_reclaim != NULL) {
                long delta;

                /*
                 * Reclaimed memory should be reapable (not included in the
                 * depot's working set).
                 */
                delta = cp->cache_full.ml_total;
                cp->cache_reclaim(cp->cache_private);
                delta = cp->cache_full.ml_total - delta;
                if (delta > 0) {
                        mutex_enter(&cp->cache_depot_lock);
                        cp->cache_full.ml_reaplimit += delta;
                        cp->cache_full.ml_min += delta;
                        mutex_exit(&cp->cache_depot_lock);
                }
        }

        kmem_depot_ws_reap(cp);

        if (cp->cache_defrag != NULL && !kmem_move_noreap) {
                kmem_cache_defrag(cp);
        }
}

static void
kmem_reap_timeout(void *flag_arg)
{
        uint32_t *flag = (uint32_t *)flag_arg;

        ASSERT(flag == &kmem_reaping || flag == &kmem_reaping_idspace);
        *flag = 0;
}

static void
kmem_reap_done(void *flag)
{
        if (!callout_init_done) {
                /* can't schedule a timeout at this point */
                kmem_reap_timeout(flag);
        } else {
                (void) timeout(kmem_reap_timeout, flag, kmem_reap_interval);
        }
}

static void
kmem_reap_start(void *flag)
{
        ASSERT(flag == &kmem_reaping || flag == &kmem_reaping_idspace);

        if (flag == &kmem_reaping) {
                kmem_cache_applyall(kmem_cache_reap, kmem_taskq, TQ_NOSLEEP);
                /*
                 * if we have segkp under heap, reap segkp cache.
                 */
                if (segkp_fromheap)
                        segkp_cache_free();
        }
        else
                kmem_cache_applyall_id(kmem_cache_reap, kmem_taskq, TQ_NOSLEEP);

        /*
         * We use taskq_dispatch() to schedule a timeout to clear
         * the flag so that kmem_reap() becomes self-throttling:
         * we won't reap again until the current reap completes *and*
         * at least kmem_reap_interval ticks have elapsed.
         */
        if (!taskq_dispatch(kmem_taskq, kmem_reap_done, flag, TQ_NOSLEEP))
                kmem_reap_done(flag);
}

static void
kmem_reap_common(void *flag_arg)
{
        uint32_t *flag = (uint32_t *)flag_arg;

        if (MUTEX_HELD(&kmem_cache_lock) || kmem_taskq == NULL ||
            atomic_cas_32(flag, 0, 1) != 0)
                return;

        /*
         * It may not be kosher to do memory allocation when a reap is called
         * (for example, if vmem_populate() is in the call chain).  So we
         * start the reap going with a TQ_NOALLOC dispatch.  If the dispatch
         * fails, we reset the flag, and the next reap will try again.
         */
        if (!taskq_dispatch(kmem_taskq, kmem_reap_start, flag, TQ_NOALLOC))
                *flag = 0;
}

/*
 * Reclaim all unused memory from all caches.  Called from the VM system
 * when memory gets tight.
 */
void
kmem_reap(void)
{
        kmem_reap_common(&kmem_reaping);
}

/*
 * Reclaim all unused memory from identifier arenas, called when a vmem
 * arena not back by memory is exhausted.  Since reaping memory-backed caches
 * cannot help with identifier exhaustion, we avoid both a large amount of
 * work and unwanted side-effects from reclaim callbacks.
 */
void
kmem_reap_idspace(void)
{
        kmem_reap_common(&kmem_reaping_idspace);
}

/*
 * Purge all magazines from a cache and set its magazine limit to zero.
 * All calls are serialized by the kmem_taskq lock, except for the final
 * call from kmem_cache_destroy().
 */
static void
kmem_cache_magazine_purge(kmem_cache_t *cp)
{
        kmem_cpu_cache_t *ccp;
        kmem_magazine_t *mp, *pmp;
        int rounds, prounds, cpu_seqid;

        ASSERT(!list_link_active(&cp->cache_link) ||
            taskq_member(kmem_taskq, curthread));
        ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));

        for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
                ccp = &cp->cache_cpu[cpu_seqid];

                mutex_enter(&ccp->cc_lock);
                mp = ccp->cc_loaded;
                pmp = ccp->cc_ploaded;
                rounds = ccp->cc_rounds;
                prounds = ccp->cc_prounds;
                ccp->cc_loaded = NULL;
                ccp->cc_ploaded = NULL;
                ccp->cc_rounds = -1;
                ccp->cc_prounds = -1;
                ccp->cc_magsize = 0;
                mutex_exit(&ccp->cc_lock);

                if (mp)
                        kmem_magazine_destroy(cp, mp, rounds);
                if (pmp)
                        kmem_magazine_destroy(cp, pmp, prounds);
        }

        kmem_depot_ws_zero(cp);
        kmem_depot_ws_reap(cp);
}

/*
 * Enable per-cpu magazines on a cache.
 */
static void
kmem_cache_magazine_enable(kmem_cache_t *cp)
{
        int cpu_seqid;

        if (cp->cache_flags & KMF_NOMAGAZINE)
                return;

        for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
                kmem_cpu_cache_t *ccp = &cp->cache_cpu[cpu_seqid];
                mutex_enter(&ccp->cc_lock);
                ccp->cc_magsize = cp->cache_magtype->mt_magsize;
                mutex_exit(&ccp->cc_lock);
        }

}

/*
 * Reap (almost) everything right now.
 */
void
kmem_cache_reap_now(kmem_cache_t *cp)
{
        ASSERT(list_link_active(&cp->cache_link));

        kmem_depot_ws_zero(cp);

        (void) taskq_dispatch(kmem_taskq,
            (task_func_t *)kmem_depot_ws_reap, cp, TQ_SLEEP);
        taskq_wait(kmem_taskq);
}

/*
 * Recompute a cache's magazine size.  The trade-off is that larger magazines
 * provide a higher transfer rate with the depot, while smaller magazines
 * reduce memory consumption.  Magazine resizing is an expensive operation;
 * it should not be done frequently.
 *
 * Changes to the magazine size are serialized by the kmem_taskq lock.
 *
 * Note: at present this only grows the magazine size.  It might be useful
 * to allow shrinkage too.
 */
static void
kmem_cache_magazine_resize(kmem_cache_t *cp)
{
        kmem_magtype_t *mtp = cp->cache_magtype;

        ASSERT(taskq_member(kmem_taskq, curthread));

        if (cp->cache_chunksize < mtp->mt_maxbuf) {
                kmem_cache_magazine_purge(cp);
                mutex_enter(&cp->cache_depot_lock);
                cp->cache_magtype = ++mtp;
                cp->cache_depot_contention_prev =
                    cp->cache_depot_contention + INT_MAX;
                mutex_exit(&cp->cache_depot_lock);
                kmem_cache_magazine_enable(cp);
        }
}

/*
 * Rescale a cache's hash table, so that the table size is roughly the
 * cache size.  We want the average lookup time to be extremely small.
 */
static void
kmem_hash_rescale(kmem_cache_t *cp)
{
        kmem_bufctl_t **old_table, **new_table, *bcp;
        size_t old_size, new_size, h;

        ASSERT(taskq_member(kmem_taskq, curthread));

        new_size = MAX(KMEM_HASH_INITIAL,
            1 << (highbit(3 * cp->cache_buftotal + 4) - 2));
        old_size = cp->cache_hash_mask + 1;

        if ((old_size >> 1) <= new_size && new_size <= (old_size << 1))
                return;

        new_table = vmem_alloc(kmem_hash_arena, new_size * sizeof (void *),
            VM_NOSLEEP);
        if (new_table == NULL)
                return;
        bzero(new_table, new_size * sizeof (void *));

        mutex_enter(&cp->cache_lock);

        old_size = cp->cache_hash_mask + 1;
        old_table = cp->cache_hash_table;

        cp->cache_hash_mask = new_size - 1;
        cp->cache_hash_table = new_table;
        cp->cache_rescale++;

        for (h = 0; h < old_size; h++) {
                bcp = old_table[h];
                while (bcp != NULL) {
                        void *addr = bcp->bc_addr;
                        kmem_bufctl_t *next_bcp = bcp->bc_next;
                        kmem_bufctl_t **hash_bucket = KMEM_HASH(cp, addr);
                        bcp->bc_next = *hash_bucket;
                        *hash_bucket = bcp;
                        bcp = next_bcp;
                }
        }

        mutex_exit(&cp->cache_lock);

        vmem_free(kmem_hash_arena, old_table, old_size * sizeof (void *));
}

/*
 * Perform periodic maintenance on a cache: hash rescaling, depot working-set
 * update, magazine resizing, and slab consolidation.
 */
static void
kmem_cache_update(kmem_cache_t *cp)
{
        int need_hash_rescale = 0;
        int need_magazine_resize = 0;

        ASSERT(MUTEX_HELD(&kmem_cache_lock));

        /*
         * If the cache has become much larger or smaller than its hash table,
         * fire off a request to rescale the hash table.
         */
        mutex_enter(&cp->cache_lock);

        if ((cp->cache_flags & KMF_HASH) &&
            (cp->cache_buftotal > (cp->cache_hash_mask << 1) ||
            (cp->cache_buftotal < (cp->cache_hash_mask >> 1) &&
            cp->cache_hash_mask > KMEM_HASH_INITIAL)))
                need_hash_rescale = 1;

        mutex_exit(&cp->cache_lock);

        /*
         * Update the depot working set statistics.
         */
        kmem_depot_ws_update(cp);

        /*
         * If there's a lot of contention in the depot,
         * increase the magazine size.
         */
        mutex_enter(&cp->cache_depot_lock);

        if (cp->cache_chunksize < cp->cache_magtype->mt_maxbuf &&
            (int)(cp->cache_depot_contention -
            cp->cache_depot_contention_prev) > kmem_depot_contention)
                need_magazine_resize = 1;

        cp->cache_depot_contention_prev = cp->cache_depot_contention;

        mutex_exit(&cp->cache_depot_lock);

        if (need_hash_rescale)
                (void) taskq_dispatch(kmem_taskq,
                    (task_func_t *)kmem_hash_rescale, cp, TQ_NOSLEEP);

        if (need_magazine_resize)
                (void) taskq_dispatch(kmem_taskq,
                    (task_func_t *)kmem_cache_magazine_resize, cp, TQ_NOSLEEP);

        if (cp->cache_defrag != NULL)
                (void) taskq_dispatch(kmem_taskq,
                    (task_func_t *)kmem_cache_scan, cp, TQ_NOSLEEP);
}

static void kmem_update(void *);

static void
kmem_update_timeout(void *dummy)
{
        (void) timeout(kmem_update, dummy, kmem_reap_interval);
}

static void
kmem_update(void *dummy)
{
        kmem_cache_applyall(kmem_cache_update, NULL, TQ_NOSLEEP);

        /*
         * We use taskq_dispatch() to reschedule the timeout so that
         * kmem_update() becomes self-throttling: it won't schedule
         * new tasks until all previous tasks have completed.
         */
        if (!taskq_dispatch(kmem_taskq, kmem_update_timeout, dummy, TQ_NOSLEEP))
                kmem_update_timeout(NULL);
}

static int
kmem_cache_kstat_update(kstat_t *ksp, int rw)
{
        struct kmem_cache_kstat *kmcp = &kmem_cache_kstat;
        kmem_cache_t *cp = ksp->ks_private;
        uint64_t cpu_buf_avail;
        uint64_t buf_avail = 0;
        int cpu_seqid;
        long reap;

        ASSERT(MUTEX_HELD(&kmem_cache_kstat_lock));

        if (rw == KSTAT_WRITE)
                return (EACCES);

        mutex_enter(&cp->cache_lock);

        kmcp->kmc_alloc_fail.value.ui64         = cp->cache_alloc_fail;
        kmcp->kmc_alloc.value.ui64              = cp->cache_slab_alloc;
        kmcp->kmc_free.value.ui64               = cp->cache_slab_free;
        kmcp->kmc_slab_alloc.value.ui64         = cp->cache_slab_alloc;
        kmcp->kmc_slab_free.value.ui64          = cp->cache_slab_free;

        for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
                kmem_cpu_cache_t *ccp = &cp->cache_cpu[cpu_seqid];

                mutex_enter(&ccp->cc_lock);

                cpu_buf_avail = 0;
                if (ccp->cc_rounds > 0)
                        cpu_buf_avail += ccp->cc_rounds;
                if (ccp->cc_prounds > 0)
                        cpu_buf_avail += ccp->cc_prounds;

                kmcp->kmc_alloc.value.ui64      += ccp->cc_alloc;
                kmcp->kmc_free.value.ui64       += ccp->cc_free;
                buf_avail                       += cpu_buf_avail;

                mutex_exit(&ccp->cc_lock);
        }

        mutex_enter(&cp->cache_depot_lock);

        kmcp->kmc_depot_alloc.value.ui64        = cp->cache_full.ml_alloc;
        kmcp->kmc_depot_free.value.ui64         = cp->cache_empty.ml_alloc;
        kmcp->kmc_depot_contention.value.ui64   = cp->cache_depot_contention;
        kmcp->kmc_full_magazines.value.ui64     = cp->cache_full.ml_total;
        kmcp->kmc_empty_magazines.value.ui64    = cp->cache_empty.ml_total;
        kmcp->kmc_magazine_size.value.ui64      =
            (cp->cache_flags & KMF_NOMAGAZINE) ?
            0 : cp->cache_magtype->mt_magsize;

        kmcp->kmc_alloc.value.ui64              += cp->cache_full.ml_alloc;
        kmcp->kmc_free.value.ui64               += cp->cache_empty.ml_alloc;
        buf_avail += cp->cache_full.ml_total * cp->cache_magtype->mt_magsize;

        reap = MIN(cp->cache_full.ml_reaplimit, cp->cache_full.ml_min);
        reap = MIN(reap, cp->cache_full.ml_total);

        mutex_exit(&cp->cache_depot_lock);

        kmcp->kmc_buf_size.value.ui64   = cp->cache_bufsize;
        kmcp->kmc_align.value.ui64      = cp->cache_align;
        kmcp->kmc_chunk_size.value.ui64 = cp->cache_chunksize;
        kmcp->kmc_slab_size.value.ui64  = cp->cache_slabsize;
        kmcp->kmc_buf_constructed.value.ui64 = buf_avail;
        buf_avail += cp->cache_bufslab;
        kmcp->kmc_buf_avail.value.ui64  = buf_avail;
        kmcp->kmc_buf_inuse.value.ui64  = cp->cache_buftotal - buf_avail;
        kmcp->kmc_buf_total.value.ui64  = cp->cache_buftotal;
        kmcp->kmc_buf_max.value.ui64    = cp->cache_bufmax;
        kmcp->kmc_slab_create.value.ui64        = cp->cache_slab_create;
        kmcp->kmc_slab_destroy.value.ui64       = cp->cache_slab_destroy;
        kmcp->kmc_hash_size.value.ui64  = (cp->cache_flags & KMF_HASH) ?
            cp->cache_hash_mask + 1 : 0;
        kmcp->kmc_hash_lookup_depth.value.ui64  = cp->cache_lookup_depth;
        kmcp->kmc_hash_rescale.value.ui64       = cp->cache_rescale;
        kmcp->kmc_vmem_source.value.ui64        = cp->cache_arena->vm_id;
        kmcp->kmc_reap.value.ui64       = cp->cache_reap;

        if (cp->cache_defrag == NULL) {
                kmcp->kmc_move_callbacks.value.ui64     = 0;
                kmcp->kmc_move_yes.value.ui64           = 0;
                kmcp->kmc_move_no.value.ui64            = 0;
                kmcp->kmc_move_later.value.ui64         = 0;
                kmcp->kmc_move_dont_need.value.ui64     = 0;
                kmcp->kmc_move_dont_know.value.ui64     = 0;
                kmcp->kmc_move_hunt_found.value.ui64    = 0;
                kmcp->kmc_move_slabs_freed.value.ui64   = 0;
                kmcp->kmc_defrag.value.ui64             = 0;
                kmcp->kmc_scan.value.ui64               = 0;
                kmcp->kmc_move_reclaimable.value.ui64   = 0;
        } else {
                int64_t reclaimable;

                kmem_defrag_t *kd = cp->cache_defrag;
                kmcp->kmc_move_callbacks.value.ui64     = kd->kmd_callbacks;
                kmcp->kmc_move_yes.value.ui64           = kd->kmd_yes;
                kmcp->kmc_move_no.value.ui64            = kd->kmd_no;
                kmcp->kmc_move_later.value.ui64         = kd->kmd_later;
                kmcp->kmc_move_dont_need.value.ui64     = kd->kmd_dont_need;
                kmcp->kmc_move_dont_know.value.ui64     = kd->kmd_dont_know;
                kmcp->kmc_move_hunt_found.value.ui64    = 0;
                kmcp->kmc_move_slabs_freed.value.ui64   = kd->kmd_slabs_freed;
                kmcp->kmc_defrag.value.ui64             = kd->kmd_defrags;
                kmcp->kmc_scan.value.ui64               = kd->kmd_scans;

                reclaimable = cp->cache_bufslab - (cp->cache_maxchunks - 1);
                reclaimable = MAX(reclaimable, 0);
                reclaimable += ((uint64_t)reap * cp->cache_magtype->mt_magsize);
                kmcp->kmc_move_reclaimable.value.ui64   = reclaimable;
        }

        mutex_exit(&cp->cache_lock);
        return (0);
}

/*
 * Return a named statistic about a particular cache.
 * This shouldn't be called very often, so it's currently designed for
 * simplicity (leverages existing kstat support) rather than efficiency.
 */
uint64_t
kmem_cache_stat(kmem_cache_t *cp, char *name)
{
        int i;
        kstat_t *ksp = cp->cache_kstat;
        kstat_named_t *knp = (kstat_named_t *)&kmem_cache_kstat;
        uint64_t value = 0;

        if (ksp != NULL) {
                mutex_enter(&kmem_cache_kstat_lock);
                (void) kmem_cache_kstat_update(ksp, KSTAT_READ);
                for (i = 0; i < ksp->ks_ndata; i++) {
                        if (strcmp(knp[i].name, name) == 0) {
                                value = knp[i].value.ui64;
                                break;
                        }
                }
                mutex_exit(&kmem_cache_kstat_lock);
        }
        return (value);
}

/*
 * Return an estimate of currently available kernel heap memory.
 * On 32-bit systems, physical memory may exceed virtual memory,
 * we just truncate the result at 1GB.
 */
size_t
kmem_avail(void)
{
        spgcnt_t rmem = availrmem - tune.t_minarmem;
        spgcnt_t fmem = freemem - minfree;

        return ((size_t)ptob(MIN(MAX(MIN(rmem, fmem), 0),
            1 << (30 - PAGESHIFT))));
}

/*
 * Return the maximum amount of memory that is (in theory) allocatable
 * from the heap. This may be used as an estimate only since there
 * is no guarentee this space will still be available when an allocation
 * request is made, nor that the space may be allocated in one big request
 * due to kernel heap fragmentation.
 */
size_t
kmem_maxavail(void)
{
        spgcnt_t pmem = availrmem - tune.t_minarmem;
        spgcnt_t vmem = btop(vmem_size(heap_arena, VMEM_FREE));

        return ((size_t)ptob(MAX(MIN(pmem, vmem), 0)));
}

/*
 * Indicate whether memory-intensive kmem debugging is enabled.
 */
int
kmem_debugging(void)
{
        return (kmem_flags & (KMF_AUDIT | KMF_REDZONE));
}

/* binning function, sorts finely at the two extremes */
#define KMEM_PARTIAL_SLAB_WEIGHT(sp, binshift)                          \
        ((((sp)->slab_refcnt <= (binshift)) ||                          \
            (((sp)->slab_chunks - (sp)->slab_refcnt) <= (binshift)))    \
            ? -(sp)->slab_refcnt                                        \
            : -((binshift) + ((sp)->slab_refcnt >> (binshift))))

/*
 * Minimizing the number of partial slabs on the freelist minimizes
 * fragmentation (the ratio of unused buffers held by the slab layer). There are
 * two ways to get a slab off of the freelist: 1) free all the buffers on the
 * slab, and 2) allocate all the buffers on the slab. It follows that we want
 * the most-used slabs at the front of the list where they have the best chance
 * of being completely allocated, and the least-used slabs at a safe distance
 * from the front to improve the odds that the few remaining buffers will all be
 * freed before another allocation can tie up the slab. For that reason a slab
 * with a higher slab_refcnt sorts less than than a slab with a lower
 * slab_refcnt.
 *
 * However, if a slab has at least one buffer that is deemed unfreeable, we
 * would rather have that slab at the front of the list regardless of
 * slab_refcnt, since even one unfreeable buffer makes the entire slab
 * unfreeable. If the client returns KMEM_CBRC_NO in response to a cache_move()
 * callback, the slab is marked unfreeable for as long as it remains on the
 * freelist.
 */
static int
kmem_partial_slab_cmp(const void *p0, const void *p1)
{
        const kmem_cache_t *cp;
        const kmem_slab_t *s0 = p0;
        const kmem_slab_t *s1 = p1;
        int w0, w1;
        size_t binshift;

        ASSERT(KMEM_SLAB_IS_PARTIAL(s0));
        ASSERT(KMEM_SLAB_IS_PARTIAL(s1));
        ASSERT(s0->slab_cache == s1->slab_cache);
        cp = s1->slab_cache;
        ASSERT(MUTEX_HELD(&cp->cache_lock));
        binshift = cp->cache_partial_binshift;

        /* weight of first slab */
        w0 = KMEM_PARTIAL_SLAB_WEIGHT(s0, binshift);
        if (s0->slab_flags & KMEM_SLAB_NOMOVE) {
                w0 -= cp->cache_maxchunks;
        }

        /* weight of second slab */
        w1 = KMEM_PARTIAL_SLAB_WEIGHT(s1, binshift);
        if (s1->slab_flags & KMEM_SLAB_NOMOVE) {
                w1 -= cp->cache_maxchunks;
        }

        if (w0 < w1)
                return (-1);
        if (w0 > w1)
                return (1);

        /* compare pointer values */
        if ((uintptr_t)s0 < (uintptr_t)s1)
                return (-1);
        if ((uintptr_t)s0 > (uintptr_t)s1)
                return (1);

        return (0);
}

/*
 * It must be valid to call the destructor (if any) on a newly created object.
 * That is, the constructor (if any) must leave the object in a valid state for
 * the destructor.
 */
kmem_cache_t *
kmem_cache_create(
        char *name,             /* descriptive name for this cache */
        size_t bufsize,         /* size of the objects it manages */
        size_t align,           /* required object alignment */
        int (*constructor)(void *, void *, int), /* object constructor */
        void (*destructor)(void *, void *),     /* object destructor */
        void (*reclaim)(void *), /* memory reclaim callback */
        void *private,          /* pass-thru arg for constr/destr/reclaim */
        vmem_t *vmp,            /* vmem source for slab allocation */
        int cflags)             /* cache creation flags */
{
        int cpu_seqid;
        size_t chunksize;
        kmem_cache_t *cp;
        kmem_magtype_t *mtp;
        size_t csize = KMEM_CACHE_SIZE(max_ncpus);

#ifdef  DEBUG
        /*
         * Cache names should conform to the rules for valid C identifiers
         */
        if (!strident_valid(name)) {
                cmn_err(CE_CONT,
                    "kmem_cache_create: '%s' is an invalid cache name\n"
                    "cache names must conform to the rules for "
                    "C identifiers\n", name);
        }
#endif  /* DEBUG */

        if (vmp == NULL)
                vmp = kmem_default_arena;

        /*
         * If this kmem cache has an identifier vmem arena as its source, mark
         * it such to allow kmem_reap_idspace().
         */
        ASSERT(!(cflags & KMC_IDENTIFIER));   /* consumer should not set this */
        if (vmp->vm_cflags & VMC_IDENTIFIER)
                cflags |= KMC_IDENTIFIER;

        /*
         * Get a kmem_cache structure.  We arrange that cp->cache_cpu[]
         * is aligned on a KMEM_CPU_CACHE_SIZE boundary to prevent
         * false sharing of per-CPU data.
         */
        cp = vmem_xalloc(kmem_cache_arena, csize, KMEM_CPU_CACHE_SIZE,
            P2NPHASE(csize, KMEM_CPU_CACHE_SIZE), 0, NULL, NULL, VM_SLEEP);
        bzero(cp, csize);
        list_link_init(&cp->cache_link);

        if (align == 0)
                align = KMEM_ALIGN;

        /*
         * If we're not at least KMEM_ALIGN aligned, we can't use free
         * memory to hold bufctl information (because we can't safely
         * perform word loads and stores on it).
         */
        if (align < KMEM_ALIGN)
                cflags |= KMC_NOTOUCH;

        if (!ISP2(align) || align > vmp->vm_quantum)
                panic("kmem_cache_create: bad alignment %lu", align);

        mutex_enter(&kmem_flags_lock);
        if (kmem_flags & KMF_RANDOMIZE)
                kmem_flags = (((kmem_flags | ~KMF_RANDOM) + 1) & KMF_RANDOM) |
                    KMF_RANDOMIZE;
        cp->cache_flags = (kmem_flags | cflags) & KMF_DEBUG;
        mutex_exit(&kmem_flags_lock);

        /*
         * Make sure all the various flags are reasonable.
         */
        ASSERT(!(cflags & KMC_NOHASH) || !(cflags & KMC_NOTOUCH));

        if (cp->cache_flags & KMF_LITE) {
                if (bufsize >= kmem_lite_minsize &&
                    align <= kmem_lite_maxalign &&
                    P2PHASE(bufsize, kmem_lite_maxalign) != 0) {
                        cp->cache_flags |= KMF_BUFTAG;
                        cp->cache_flags &= ~(KMF_AUDIT | KMF_FIREWALL);
                } else {
                        cp->cache_flags &= ~KMF_DEBUG;
                }
        }

        if (cp->cache_flags & KMF_DEADBEEF)
                cp->cache_flags |= KMF_REDZONE;

        if ((cflags & KMC_QCACHE) && (cp->cache_flags & KMF_AUDIT))
                cp->cache_flags |= KMF_NOMAGAZINE;

        if (cflags & KMC_NODEBUG)
                cp->cache_flags &= ~KMF_DEBUG;

        if (cflags & KMC_NOTOUCH)
                cp->cache_flags &= ~KMF_TOUCH;

        if (cflags & KMC_PREFILL)
                cp->cache_flags |= KMF_PREFILL;

        if (cflags & KMC_NOHASH)
                cp->cache_flags &= ~(KMF_AUDIT | KMF_FIREWALL);

        if (cflags & KMC_NOMAGAZINE)
                cp->cache_flags |= KMF_NOMAGAZINE;

        if ((cp->cache_flags & KMF_AUDIT) && !(cflags & KMC_NOTOUCH))
                cp->cache_flags |= KMF_REDZONE;

        if (!(cp->cache_flags & KMF_AUDIT))
                cp->cache_flags &= ~KMF_CONTENTS;

        if ((cp->cache_flags & KMF_BUFTAG) && bufsize >= kmem_minfirewall &&
            !(cp->cache_flags & KMF_LITE) && !(cflags & KMC_NOHASH))
                cp->cache_flags |= KMF_FIREWALL;

        if (vmp != kmem_default_arena || kmem_firewall_arena == NULL)
                cp->cache_flags &= ~KMF_FIREWALL;

        if (cp->cache_flags & KMF_FIREWALL) {
                cp->cache_flags &= ~KMF_BUFTAG;
                cp->cache_flags |= KMF_NOMAGAZINE;
                ASSERT(vmp == kmem_default_arena);
                vmp = kmem_firewall_arena;
        }

        /*
         * Set cache properties.
         */
        (void) strncpy(cp->cache_name, name, KMEM_CACHE_NAMELEN);
        strident_canon(cp->cache_name, KMEM_CACHE_NAMELEN + 1);
        cp->cache_bufsize = bufsize;
        cp->cache_align = align;
        cp->cache_constructor = constructor;
        cp->cache_destructor = destructor;
        cp->cache_reclaim = reclaim;
        cp->cache_private = private;
        cp->cache_arena = vmp;
        cp->cache_cflags = cflags;

        /*
         * Determine the chunk size.
         */
        chunksize = bufsize;

        if (align >= KMEM_ALIGN) {
                chunksize = P2ROUNDUP(chunksize, KMEM_ALIGN);
                cp->cache_bufctl = chunksize - KMEM_ALIGN;
        }

        if (cp->cache_flags & KMF_BUFTAG) {
                cp->cache_bufctl = chunksize;
                cp->cache_buftag = chunksize;
                if (cp->cache_flags & KMF_LITE)
                        chunksize += KMEM_BUFTAG_LITE_SIZE(kmem_lite_count);
                else
                        chunksize += sizeof (kmem_buftag_t);
        }

        if (cp->cache_flags & KMF_DEADBEEF) {
                cp->cache_verify = MIN(cp->cache_buftag, kmem_maxverify);
                if (cp->cache_flags & KMF_LITE)
                        cp->cache_verify = sizeof (uint64_t);
        }

        cp->cache_contents = MIN(cp->cache_bufctl, kmem_content_maxsave);

        cp->cache_chunksize = chunksize = P2ROUNDUP(chunksize, align);

        /*
         * Now that we know the chunk size, determine the optimal slab size.
         */
        if (vmp == kmem_firewall_arena) {
                cp->cache_slabsize = P2ROUNDUP(chunksize, vmp->vm_quantum);
                cp->cache_mincolor = cp->cache_slabsize - chunksize;
                cp->cache_maxcolor = cp->cache_mincolor;
                cp->cache_flags |= KMF_HASH;
                ASSERT(!(cp->cache_flags & KMF_BUFTAG));
        } else if ((cflags & KMC_NOHASH) || (!(cflags & KMC_NOTOUCH) &&
            !(cp->cache_flags & KMF_AUDIT) &&
            chunksize < vmp->vm_quantum / KMEM_VOID_FRACTION)) {
                cp->cache_slabsize = vmp->vm_quantum;
                cp->cache_mincolor = 0;
                cp->cache_maxcolor =
                    (cp->cache_slabsize - sizeof (kmem_slab_t)) % chunksize;
                ASSERT(chunksize + sizeof (kmem_slab_t) <= cp->cache_slabsize);
                ASSERT(!(cp->cache_flags & KMF_AUDIT));
        } else {
                size_t chunks, bestfit, waste, slabsize;
                size_t minwaste = LONG_MAX;

                for (chunks = 1; chunks <= KMEM_VOID_FRACTION; chunks++) {
                        slabsize = P2ROUNDUP(chunksize * chunks,
                            vmp->vm_quantum);
                        chunks = slabsize / chunksize;
                        waste = (slabsize % chunksize) / chunks;
                        if (waste < minwaste) {
                                minwaste = waste;
                                bestfit = slabsize;
                        }
                }
                if (cflags & KMC_QCACHE)
                        bestfit = VMEM_QCACHE_SLABSIZE(vmp->vm_qcache_max);
                cp->cache_slabsize = bestfit;
                cp->cache_mincolor = 0;
                cp->cache_maxcolor = bestfit % chunksize;
                cp->cache_flags |= KMF_HASH;
        }

        cp->cache_maxchunks = (cp->cache_slabsize / cp->cache_chunksize);
        cp->cache_partial_binshift = highbit(cp->cache_maxchunks / 16) + 1;

        /*
         * Disallowing prefill when either the DEBUG or HASH flag is set or when
         * there is a constructor avoids some tricky issues with debug setup
         * that may be revisited later. We cannot allow prefill in a
         * metadata cache because of potential recursion.
         */
        if (vmp == kmem_msb_arena ||
            cp->cache_flags & (KMF_HASH | KMF_BUFTAG) ||
            cp->cache_constructor != NULL)
                cp->cache_flags &= ~KMF_PREFILL;

        if (cp->cache_flags & KMF_HASH) {
                ASSERT(!(cflags & KMC_NOHASH));
                cp->cache_bufctl_cache = (cp->cache_flags & KMF_AUDIT) ?
                    kmem_bufctl_audit_cache : kmem_bufctl_cache;
        }

        if (cp->cache_maxcolor >= vmp->vm_quantum)
                cp->cache_maxcolor = vmp->vm_quantum - 1;

        cp->cache_color = cp->cache_mincolor;

        /*
         * Initialize the rest of the slab layer.
         */
        mutex_init(&cp->cache_lock, NULL, MUTEX_DEFAULT, NULL);

        avl_create(&cp->cache_partial_slabs, kmem_partial_slab_cmp,
            sizeof (kmem_slab_t), offsetof(kmem_slab_t, slab_link));
        ASSERT(sizeof (list_node_t) <= sizeof (avl_node_t));
        /* reuse partial slab AVL linkage for complete slab list linkage */
        list_create(&cp->cache_complete_slabs,
            sizeof (kmem_slab_t), offsetof(kmem_slab_t, slab_link));

        if (cp->cache_flags & KMF_HASH) {
                cp->cache_hash_table = vmem_alloc(kmem_hash_arena,
                    KMEM_HASH_INITIAL * sizeof (void *), VM_SLEEP);
                bzero(cp->cache_hash_table,
                    KMEM_HASH_INITIAL * sizeof (void *));
                cp->cache_hash_mask = KMEM_HASH_INITIAL - 1;
                cp->cache_hash_shift = highbit((ulong_t)chunksize) - 1;
        }

        /*
         * Initialize the depot.
         */
        mutex_init(&cp->cache_depot_lock, NULL, MUTEX_DEFAULT, NULL);

        for (mtp = kmem_magtype; chunksize <= mtp->mt_minbuf; mtp++)
                continue;

        cp->cache_magtype = mtp;

        /*
         * Initialize the CPU layer.
         */
        for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++) {
                kmem_cpu_cache_t *ccp = &cp->cache_cpu[cpu_seqid];
                mutex_init(&ccp->cc_lock, NULL, MUTEX_DEFAULT, NULL);
                ccp->cc_flags = cp->cache_flags;
                ccp->cc_rounds = -1;
                ccp->cc_prounds = -1;
        }

        /*
         * Create the cache's kstats.
         */
        if ((cp->cache_kstat = kstat_create("unix", 0, cp->cache_name,
            "kmem_cache", KSTAT_TYPE_NAMED,
            sizeof (kmem_cache_kstat) / sizeof (kstat_named_t),
            KSTAT_FLAG_VIRTUAL)) != NULL) {
                cp->cache_kstat->ks_data = &kmem_cache_kstat;
                cp->cache_kstat->ks_update = kmem_cache_kstat_update;
                cp->cache_kstat->ks_private = cp;
                cp->cache_kstat->ks_lock = &kmem_cache_kstat_lock;
                kstat_install(cp->cache_kstat);
        }

        /*
         * Add the cache to the global list.  This makes it visible
         * to kmem_update(), so the cache must be ready for business.
         */
        mutex_enter(&kmem_cache_lock);
        list_insert_tail(&kmem_caches, cp);
        mutex_exit(&kmem_cache_lock);

        if (kmem_ready)
                kmem_cache_magazine_enable(cp);

        return (cp);
}

static int
kmem_move_cmp(const void *buf, const void *p)
{
        const kmem_move_t *kmm = p;
        uintptr_t v1 = (uintptr_t)buf;
        uintptr_t v2 = (uintptr_t)kmm->kmm_from_buf;
        return (v1 < v2 ? -1 : (v1 > v2 ? 1 : 0));
}

static void
kmem_reset_reclaim_threshold(kmem_defrag_t *kmd)
{
        kmd->kmd_reclaim_numer = 1;
}

/*
 * Initially, when choosing candidate slabs for buffers to move, we want to be
 * very selective and take only slabs that are less than
 * (1 / KMEM_VOID_FRACTION) allocated. If we have difficulty finding candidate
 * slabs, then we raise the allocation ceiling incrementally. The reclaim
 * threshold is reset to (1 / KMEM_VOID_FRACTION) as soon as the cache is no
 * longer fragmented.
 */
static void
kmem_adjust_reclaim_threshold(kmem_defrag_t *kmd, int direction)
{
        if (direction > 0) {
                /* make it easier to find a candidate slab */
                if (kmd->kmd_reclaim_numer < (KMEM_VOID_FRACTION - 1)) {
                        kmd->kmd_reclaim_numer++;
                }
        } else {
                /* be more selective */
                if (kmd->kmd_reclaim_numer > 1) {
                        kmd->kmd_reclaim_numer--;
                }
        }
}

void
kmem_cache_set_move(kmem_cache_t *cp,
    kmem_cbrc_t (*move)(void *, void *, size_t, void *))
{
        kmem_defrag_t *defrag;

        ASSERT(move != NULL);
        /*
         * The consolidator does not support NOTOUCH caches because kmem cannot
         * initialize their slabs with the 0xbaddcafe memory pattern, which sets
         * a low order bit usable by clients to distinguish uninitialized memory
         * from known objects (see kmem_slab_create).
         */
        ASSERT(!(cp->cache_cflags & KMC_NOTOUCH));
        ASSERT(!(cp->cache_cflags & KMC_IDENTIFIER));

        /*
         * We should not be holding anyone's cache lock when calling
         * kmem_cache_alloc(), so allocate in all cases before acquiring the
         * lock.
         */
        defrag = kmem_cache_alloc(kmem_defrag_cache, KM_SLEEP);

        mutex_enter(&cp->cache_lock);

        if (KMEM_IS_MOVABLE(cp)) {
                if (cp->cache_move == NULL) {
                        ASSERT(cp->cache_slab_alloc == 0);

                        cp->cache_defrag = defrag;
                        defrag = NULL; /* nothing to free */
                        bzero(cp->cache_defrag, sizeof (kmem_defrag_t));
                        avl_create(&cp->cache_defrag->kmd_moves_pending,
                            kmem_move_cmp, sizeof (kmem_move_t),
                            offsetof(kmem_move_t, kmm_entry));
                        ASSERT(sizeof (list_node_t) <= sizeof (avl_node_t));
                        /* reuse the slab's AVL linkage for deadlist linkage */
                        list_create(&cp->cache_defrag->kmd_deadlist,
                            sizeof (kmem_slab_t),
                            offsetof(kmem_slab_t, slab_link));
                        kmem_reset_reclaim_threshold(cp->cache_defrag);
                }
                cp->cache_move = move;
        }

        mutex_exit(&cp->cache_lock);

        if (defrag != NULL) {
                kmem_cache_free(kmem_defrag_cache, defrag); /* unused */
        }
}

void
kmem_cache_destroy(kmem_cache_t *cp)
{
        int cpu_seqid;

        /*
         * Remove the cache from the global cache list so that no one else
         * can schedule tasks on its behalf, wait for any pending tasks to
         * complete, purge the cache, and then destroy it.
         */
        mutex_enter(&kmem_cache_lock);
        list_remove(&kmem_caches, cp);
        mutex_exit(&kmem_cache_lock);

        if (kmem_taskq != NULL)
                taskq_wait(kmem_taskq);

        if (kmem_move_taskq != NULL && cp->cache_defrag != NULL)
                taskq_wait(kmem_move_taskq);

        kmem_cache_magazine_purge(cp);

        mutex_enter(&cp->cache_lock);
        if (cp->cache_buftotal != 0)
                cmn_err(CE_WARN, "kmem_cache_destroy: '%s' (%p) not empty",
                    cp->cache_name, (void *)cp);
        if (cp->cache_defrag != NULL) {
                avl_destroy(&cp->cache_defrag->kmd_moves_pending);
                list_destroy(&cp->cache_defrag->kmd_deadlist);
                kmem_cache_free(kmem_defrag_cache, cp->cache_defrag);
                cp->cache_defrag = NULL;
        }
        /*
         * The cache is now dead.  There should be no further activity.  We
         * enforce this by setting land mines in the constructor, destructor,
         * reclaim, and move routines that induce a kernel text fault if
         * invoked.
         */
        cp->cache_constructor = (int (*)(void *, void *, int))1;
        cp->cache_destructor = (void (*)(void *, void *))2;
        cp->cache_reclaim = (void (*)(void *))3;
        cp->cache_move = (kmem_cbrc_t (*)(void *, void *, size_t, void *))4;
        mutex_exit(&cp->cache_lock);

        kstat_delete(cp->cache_kstat);

        if (cp->cache_hash_table != NULL)
                vmem_free(kmem_hash_arena, cp->cache_hash_table,
                    (cp->cache_hash_mask + 1) * sizeof (void *));

        for (cpu_seqid = 0; cpu_seqid < max_ncpus; cpu_seqid++)
                mutex_destroy(&cp->cache_cpu[cpu_seqid].cc_lock);

        mutex_destroy(&cp->cache_depot_lock);
        mutex_destroy(&cp->cache_lock);

        vmem_free(kmem_cache_arena, cp, KMEM_CACHE_SIZE(max_ncpus));
}

/*ARGSUSED*/
static int
kmem_cpu_setup(cpu_setup_t what, int id, void *arg)
{
        ASSERT(MUTEX_HELD(&cpu_lock));
        if (what == CPU_UNCONFIG) {
                kmem_cache_applyall(kmem_cache_magazine_purge,
                    kmem_taskq, TQ_SLEEP);
                kmem_cache_applyall(kmem_cache_magazine_enable,
                    kmem_taskq, TQ_SLEEP);
        }
        return (0);
}

static void
kmem_alloc_caches_create(const int *array, size_t count,
    kmem_cache_t **alloc_table, size_t maxbuf, uint_t shift)
{
        char name[KMEM_CACHE_NAMELEN + 1];
        size_t table_unit = (1 << shift); /* range of one alloc_table entry */
        size_t size = table_unit;
        int i;

        for (i = 0; i < count; i++) {
                size_t cache_size = array[i];
                size_t align = KMEM_ALIGN;
                kmem_cache_t *cp;

                /* if the table has an entry for maxbuf, we're done */
                if (size > maxbuf)
                        break;

                /* cache size must be a multiple of the table unit */
                ASSERT(P2PHASE(cache_size, table_unit) == 0);

                /*
                 * If they allocate a multiple of the coherency granularity,
                 * they get a coherency-granularity-aligned address.
                 */
                if (IS_P2ALIGNED(cache_size, 64))
                        align = 64;
                if (IS_P2ALIGNED(cache_size, PAGESIZE))
                        align = PAGESIZE;
                (void) snprintf(name, sizeof (name),
                    "kmem_alloc_%lu", cache_size);
                cp = kmem_cache_create(name, cache_size, align,
                    NULL, NULL, NULL, NULL, NULL, KMC_KMEM_ALLOC);

                while (size <= cache_size) {
                        alloc_table[(size - 1) >> shift] = cp;
                        size += table_unit;
                }
        }

        ASSERT(size > maxbuf);          /* i.e. maxbuf <= max(cache_size) */
}

static void
kmem_cache_init(int pass, int use_large_pages)
{
        int i;
        size_t maxbuf;
        kmem_magtype_t *mtp;

        for (i = 0; i < sizeof (kmem_magtype) / sizeof (*mtp); i++) {
                char name[KMEM_CACHE_NAMELEN + 1];

                mtp = &kmem_magtype[i];
                (void) sprintf(name, "kmem_magazine_%d", mtp->mt_magsize);
                mtp->mt_cache = kmem_cache_create(name,
                    (mtp->mt_magsize + 1) * sizeof (void *),
                    mtp->mt_align, NULL, NULL, NULL, NULL,
                    kmem_msb_arena, KMC_NOHASH);
        }

        kmem_slab_cache = kmem_cache_create("kmem_slab_cache",
            sizeof (kmem_slab_t), 0, NULL, NULL, NULL, NULL,
            kmem_msb_arena, KMC_NOHASH);

        kmem_bufctl_cache = kmem_cache_create("kmem_bufctl_cache",
            sizeof (kmem_bufctl_t), 0, NULL, NULL, NULL, NULL,
            kmem_msb_arena, KMC_NOHASH);

        kmem_bufctl_audit_cache = kmem_cache_create("kmem_bufctl_audit_cache",
            sizeof (kmem_bufctl_audit_t), 0, NULL, NULL, NULL, NULL,
            kmem_msb_arena, KMC_NOHASH);

        if (pass == 2) {
                kmem_va_arena = vmem_create("kmem_va",
                    NULL, 0, PAGESIZE,
                    vmem_alloc, vmem_free, heap_arena,
                    8 * PAGESIZE, VM_SLEEP);

                if (use_large_pages) {
                        kmem_default_arena = vmem_xcreate("kmem_default",
                            NULL, 0, PAGESIZE,
                            segkmem_alloc_lp, segkmem_free_lp, kmem_va_arena,
                            0, VMC_DUMPSAFE | VM_SLEEP);
                } else {
                        kmem_default_arena = vmem_create("kmem_default",
                            NULL, 0, PAGESIZE,
                            segkmem_alloc, segkmem_free, kmem_va_arena,
                            0, VMC_DUMPSAFE | VM_SLEEP);
                }

                /* Figure out what our maximum cache size is */
                maxbuf = kmem_max_cached;
                if (maxbuf <= KMEM_MAXBUF) {
                        maxbuf = 0;
                        kmem_max_cached = KMEM_MAXBUF;
                } else {
                        size_t size = 0;
                        size_t max =
                            sizeof (kmem_big_alloc_sizes) / sizeof (int);
                        /*
                         * Round maxbuf up to an existing cache size.  If maxbuf
                         * is larger than the largest cache, we truncate it to
                         * the largest cache's size.
                         */
                        for (i = 0; i < max; i++) {
                                size = kmem_big_alloc_sizes[i];
                                if (maxbuf <= size)
                                        break;
                        }
                        kmem_max_cached = maxbuf = size;
                }

                /*
                 * The big alloc table may not be completely overwritten, so
                 * we clear out any stale cache pointers from the first pass.
                 */
                bzero(kmem_big_alloc_table, sizeof (kmem_big_alloc_table));
        } else {
                /*
                 * During the first pass, the kmem_alloc_* caches
                 * are treated as metadata.
                 */
                kmem_default_arena = kmem_msb_arena;
                maxbuf = KMEM_BIG_MAXBUF_32BIT;
        }

        /*
         * Set up the default caches to back kmem_alloc()
         */
        kmem_alloc_caches_create(
            kmem_alloc_sizes, sizeof (kmem_alloc_sizes) / sizeof (int),
            kmem_alloc_table, KMEM_MAXBUF, KMEM_ALIGN_SHIFT);

        kmem_alloc_caches_create(
            kmem_big_alloc_sizes, sizeof (kmem_big_alloc_sizes) / sizeof (int),
            kmem_big_alloc_table, maxbuf, KMEM_BIG_SHIFT);

        kmem_big_alloc_table_max = maxbuf >> KMEM_BIG_SHIFT;
}

void
kmem_init(void)
{
        kmem_cache_t *cp;
        int old_kmem_flags = kmem_flags;
        int use_large_pages = 0;
        size_t maxverify, minfirewall;

        kstat_init();

        /*
         * Don't do firewalled allocations if the heap is less than 1TB
         * (i.e. on a 32-bit kernel)
         * The resulting VM_NEXTFIT allocations would create too much
         * fragmentation in a small heap.
         */
#if defined(_LP64)
        maxverify = minfirewall = PAGESIZE / 2;
#else
        maxverify = minfirewall = ULONG_MAX;
#endif

        ASSERT(sizeof (kmem_cpu_cache_t) == KMEM_CPU_CACHE_SIZE);

        list_create(&kmem_caches, sizeof (kmem_cache_t),
            offsetof(kmem_cache_t, cache_link));

        kmem_metadata_arena = vmem_create("kmem_metadata", NULL, 0, PAGESIZE,
            vmem_alloc, vmem_free, heap_arena, 8 * PAGESIZE,
            VM_SLEEP | VMC_NO_QCACHE);

        kmem_msb_arena = vmem_create("kmem_msb", NULL, 0,
            PAGESIZE, segkmem_alloc, segkmem_free, kmem_metadata_arena, 0,
            VMC_DUMPSAFE | VM_SLEEP);

        kmem_cache_arena = vmem_create("kmem_cache", NULL, 0, KMEM_ALIGN,
            segkmem_alloc, segkmem_free, kmem_metadata_arena, 0, VM_SLEEP);

        kmem_hash_arena = vmem_create("kmem_hash", NULL, 0, KMEM_ALIGN,
            segkmem_alloc, segkmem_free, kmem_metadata_arena, 0, VM_SLEEP);

        kmem_log_arena = vmem_create("kmem_log", NULL, 0, KMEM_ALIGN,
            segkmem_alloc, segkmem_free, heap_arena, 0, VM_SLEEP);

        kmem_firewall_va_arena = vmem_create("kmem_firewall_va",
            NULL, 0, PAGESIZE,
            kmem_firewall_va_alloc, kmem_firewall_va_free, heap_arena,
            0, VM_SLEEP);

        kmem_firewall_arena = vmem_create("kmem_firewall", NULL, 0, PAGESIZE,
            segkmem_alloc, segkmem_free, kmem_firewall_va_arena, 0,
            VMC_DUMPSAFE | VM_SLEEP);

        /* temporary oversize arena for mod_read_system_file */
        kmem_oversize_arena = vmem_create("kmem_oversize", NULL, 0, PAGESIZE,
            segkmem_alloc, segkmem_free, heap_arena, 0, VM_SLEEP);

        kmem_reap_interval = 15 * hz;

        /*
         * Read /etc/system.  This is a chicken-and-egg problem because
         * kmem_flags may be set in /etc/system, but mod_read_system_file()
         * needs to use the allocator.  The simplest solution is to create
         * all the standard kmem caches, read /etc/system, destroy all the
         * caches we just created, and then create them all again in light
         * of the (possibly) new kmem_flags and other kmem tunables.
         */
        kmem_cache_init(1, 0);

        mod_read_system_file(boothowto & RB_ASKNAME);

        while ((cp = list_tail(&kmem_caches)) != NULL)
                kmem_cache_destroy(cp);

        vmem_destroy(kmem_oversize_arena);

        if (old_kmem_flags & KMF_STICKY)
                kmem_flags = old_kmem_flags;

        if (!(kmem_flags & KMF_AUDIT))
                vmem_seg_size = offsetof(vmem_seg_t, vs_thread);

        if (kmem_maxverify == 0)
                kmem_maxverify = maxverify;

        if (kmem_minfirewall == 0)
                kmem_minfirewall = minfirewall;

        /*
         * give segkmem a chance to figure out if we are using large pages
         * for the kernel heap
         */
        use_large_pages = segkmem_lpsetup();

        /*
         * To protect against corruption, we keep the actual number of callers
         * KMF_LITE records seperate from the tunable.  We arbitrarily clamp
         * to 16, since the overhead for small buffers quickly gets out of
         * hand.
         *
         * The real limit would depend on the needs of the largest KMC_NOHASH
         * cache.
         */
        kmem_lite_count = MIN(MAX(0, kmem_lite_pcs), 16);
        kmem_lite_pcs = kmem_lite_count;

        /*
         * Normally, we firewall oversized allocations when possible, but
         * if we are using large pages for kernel memory, and we don't have
         * any non-LITE debugging flags set, we want to allocate oversized
         * buffers from large pages, and so skip the firewalling.
         */
        if (use_large_pages &&
            ((kmem_flags & KMF_LITE) || !(kmem_flags & KMF_DEBUG))) {
                kmem_oversize_arena = vmem_xcreate("kmem_oversize", NULL, 0,
                    PAGESIZE, segkmem_alloc_lp, segkmem_free_lp, heap_arena,
                    0, VMC_DUMPSAFE | VM_SLEEP);
        } else {
                kmem_oversize_arena = vmem_create("kmem_oversize",
                    NULL, 0, PAGESIZE,
                    segkmem_alloc, segkmem_free, kmem_minfirewall < ULONG_MAX?
                    kmem_firewall_va_arena : heap_arena, 0, VMC_DUMPSAFE |
                    VM_SLEEP);
        }

        kmem_cache_init(2, use_large_pages);

        if (kmem_flags & (KMF_AUDIT | KMF_RANDOMIZE)) {
                if (kmem_transaction_log_size == 0)
                        kmem_transaction_log_size = kmem_maxavail() / 50;
                kmem_transaction_log = kmem_log_init(kmem_transaction_log_size);
        }

        if (kmem_flags & (KMF_CONTENTS | KMF_RANDOMIZE)) {
                if (kmem_content_log_size == 0)
                        kmem_content_log_size = kmem_maxavail() / 50;
                kmem_content_log = kmem_log_init(kmem_content_log_size);
        }

        kmem_failure_log = kmem_log_init(kmem_failure_log_size);

        kmem_slab_log = kmem_log_init(kmem_slab_log_size);

        /*
         * Initialize STREAMS message caches so allocb() is available.
         * This allows us to initialize the logging framework (cmn_err(9F),
         * strlog(9F), etc) so we can start recording messages.
         */
        streams_msg_init();

        /*
         * Initialize the ZSD framework in Zones so modules loaded henceforth
         * can register their callbacks.
         */
        zone_zsd_init();

        log_init();
        taskq_init();

        /*
         * Warn about invalid or dangerous values of kmem_flags.
         * Always warn about unsupported values.
         */
        if (((kmem_flags & ~(KMF_AUDIT | KMF_DEADBEEF | KMF_REDZONE |
            KMF_CONTENTS | KMF_LITE)) != 0) ||
            ((kmem_flags & KMF_LITE) && kmem_flags != KMF_LITE))
                cmn_err(CE_WARN, "kmem_flags set to unsupported value 0x%x. "
                    "See the Solaris Tunable Parameters Reference Manual.",
                    kmem_flags);

#ifdef DEBUG
        if ((kmem_flags & KMF_DEBUG) == 0)
                cmn_err(CE_NOTE, "kmem debugging disabled.");
#else
        /*
         * For non-debug kernels, the only "normal" flags are 0, KMF_LITE,
         * KMF_REDZONE, and KMF_CONTENTS (the last because it is only enabled
         * if KMF_AUDIT is set). We should warn the user about the performance
         * penalty of KMF_AUDIT or KMF_DEADBEEF if they are set and KMF_LITE
         * isn't set (since that disables AUDIT).
         */
        if (!(kmem_flags & KMF_LITE) &&
            (kmem_flags & (KMF_AUDIT | KMF_DEADBEEF)) != 0)
                cmn_err(CE_WARN, "High-overhead kmem debugging features "
                    "enabled (kmem_flags = 0x%x).  Performance degradation "
                    "and large memory overhead possible. See the Solaris "
                    "Tunable Parameters Reference Manual.", kmem_flags);
#endif /* not DEBUG */

        kmem_cache_applyall(kmem_cache_magazine_enable, NULL, TQ_SLEEP);

        kmem_ready = 1;

        /*
         * Initialize the platform-specific aligned/DMA memory allocator.
         */
        ka_init();

        /*
         * Initialize 32-bit ID cache.
         */
        id32_init();

        /*
         * Initialize the networking stack so modules loaded can
         * register their callbacks.
         */
        netstack_init();
}

static void
kmem_move_init(void)
{
        kmem_defrag_cache = kmem_cache_create("kmem_defrag_cache",
            sizeof (kmem_defrag_t), 0, NULL, NULL, NULL, NULL,
            kmem_msb_arena, KMC_NOHASH);
        kmem_move_cache = kmem_cache_create("kmem_move_cache",
            sizeof (kmem_move_t), 0, NULL, NULL, NULL, NULL,
            kmem_msb_arena, KMC_NOHASH);

        /*
         * kmem guarantees that move callbacks are sequential and that even
         * across multiple caches no two moves ever execute simultaneously.
         * Move callbacks are processed on a separate taskq so that client code
         * does not interfere with internal maintenance tasks.
         */
        kmem_move_taskq = taskq_create_instance("kmem_move_taskq", 0, 1,
            minclsyspri, 100, INT_MAX, TASKQ_PREPOPULATE);
}

void
kmem_thread_init(void)
{
        kmem_move_init();
        kmem_taskq = taskq_create_instance("kmem_taskq", 0, 1, minclsyspri,
            300, INT_MAX, TASKQ_PREPOPULATE);
}

void
kmem_mp_init(void)
{
        mutex_enter(&cpu_lock);
        register_cpu_setup_func(kmem_cpu_setup, NULL);
        mutex_exit(&cpu_lock);

        kmem_update_timeout(NULL);

        taskq_mp_init();
}

/*
 * Return the slab of the allocated buffer, or NULL if the buffer is not
 * allocated. This function may be called with a known slab address to determine
 * whether or not the buffer is allocated, or with a NULL slab address to obtain
 * an allocated buffer's slab.
 */
static kmem_slab_t *
kmem_slab_allocated(kmem_cache_t *cp, kmem_slab_t *sp, void *buf)
{
        kmem_bufctl_t *bcp, *bufbcp;

        ASSERT(MUTEX_HELD(&cp->cache_lock));
        ASSERT(sp == NULL || KMEM_SLAB_MEMBER(sp, buf));

        if (cp->cache_flags & KMF_HASH) {
                for (bcp = *KMEM_HASH(cp, buf);
                    (bcp != NULL) && (bcp->bc_addr != buf);
                    bcp = bcp->bc_next) {
                        continue;
                }
                ASSERT(sp != NULL && bcp != NULL ? sp == bcp->bc_slab : 1);
                return (bcp == NULL ? NULL : bcp->bc_slab);
        }

        if (sp == NULL) {
                sp = KMEM_SLAB(cp, buf);
        }
        bufbcp = KMEM_BUFCTL(cp, buf);
        for (bcp = sp->slab_head;
            (bcp != NULL) && (bcp != bufbcp);
            bcp = bcp->bc_next) {
                continue;
        }
        return (bcp == NULL ? sp : NULL);
}

static boolean_t
kmem_slab_is_reclaimable(kmem_cache_t *cp, kmem_slab_t *sp, int flags)
{
        long refcnt = sp->slab_refcnt;

        ASSERT(cp->cache_defrag != NULL);

        /*
         * For code coverage we want to be able to move an object within the
         * same slab (the only partial slab) even if allocating the destination
         * buffer resulted in a completely allocated slab.
         */
        if (flags & KMM_DEBUG) {
                return ((flags & KMM_DESPERATE) ||
                    ((sp->slab_flags & KMEM_SLAB_NOMOVE) == 0));
        }

        /* If we're desperate, we don't care if the client said NO. */
        if (flags & KMM_DESPERATE) {
                return (refcnt < sp->slab_chunks); /* any partial */
        }

        if (sp->slab_flags & KMEM_SLAB_NOMOVE) {
                return (B_FALSE);
        }

        if ((refcnt == 1) || kmem_move_any_partial) {
                return (refcnt < sp->slab_chunks);
        }

        /*
         * The reclaim threshold is adjusted at each kmem_cache_scan() so that
         * slabs with a progressively higher percentage of used buffers can be
         * reclaimed until the cache as a whole is no longer fragmented.
         *
         *      sp->slab_refcnt   kmd_reclaim_numer
         *      --------------- < ------------------
         *      sp->slab_chunks   KMEM_VOID_FRACTION
         */
        return ((refcnt * KMEM_VOID_FRACTION) <
            (sp->slab_chunks * cp->cache_defrag->kmd_reclaim_numer));
}

/*
 * May be called from the kmem_move_taskq, from kmem_cache_move_notify_task(),
 * or when the buffer is freed.
 */
static void
kmem_slab_move_yes(kmem_cache_t *cp, kmem_slab_t *sp, void *from_buf)
{
        ASSERT(MUTEX_HELD(&cp->cache_lock));
        ASSERT(KMEM_SLAB_MEMBER(sp, from_buf));

        if (!KMEM_SLAB_IS_PARTIAL(sp)) {
                return;
        }

        if (sp->slab_flags & KMEM_SLAB_NOMOVE) {
                if (KMEM_SLAB_OFFSET(sp, from_buf) == sp->slab_stuck_offset) {
                        avl_remove(&cp->cache_partial_slabs, sp);
                        sp->slab_flags &= ~KMEM_SLAB_NOMOVE;
                        sp->slab_stuck_offset = (uint32_t)-1;
                        avl_add(&cp->cache_partial_slabs, sp);
                }
        } else {
                sp->slab_later_count = 0;
                sp->slab_stuck_offset = (uint32_t)-1;
        }
}

static void
kmem_slab_move_no(kmem_cache_t *cp, kmem_slab_t *sp, void *from_buf)
{
        ASSERT(taskq_member(kmem_move_taskq, curthread));
        ASSERT(MUTEX_HELD(&cp->cache_lock));
        ASSERT(KMEM_SLAB_MEMBER(sp, from_buf));

        if (!KMEM_SLAB_IS_PARTIAL(sp)) {
                return;
        }

        avl_remove(&cp->cache_partial_slabs, sp);
        sp->slab_later_count = 0;
        sp->slab_flags |= KMEM_SLAB_NOMOVE;
        sp->slab_stuck_offset = KMEM_SLAB_OFFSET(sp, from_buf);
        avl_add(&cp->cache_partial_slabs, sp);
}

static void kmem_move_end(kmem_cache_t *, kmem_move_t *);

/*
 * The move callback takes two buffer addresses, the buffer to be moved, and a
 * newly allocated and constructed buffer selected by kmem as the destination.
 * It also takes the size of the buffer and an optional user argument specified
 * at cache creation time. kmem guarantees that the buffer to be moved has not
 * been unmapped by the virtual memory subsystem. Beyond that, it cannot
 * guarantee the present whereabouts of the buffer to be moved, so it is up to
 * the client to safely determine whether or not it is still using the buffer.
 * The client must not free either of the buffers passed to the move callback,
 * since kmem wants to free them directly to the slab layer. The client response
 * tells kmem which of the two buffers to free:
 *
 * YES          kmem frees the old buffer (the move was successful)
 * NO           kmem frees the new buffer, marks the slab of the old buffer
 *              non-reclaimable to avoid bothering the client again
 * LATER        kmem frees the new buffer, increments slab_later_count
 * DONT_KNOW    kmem frees the new buffer
 * DONT_NEED    kmem frees both the old buffer and the new buffer
 *
 * The pending callback argument now being processed contains both of the
 * buffers (old and new) passed to the move callback function, the slab of the
 * old buffer, and flags related to the move request, such as whether or not the
 * system was desperate for memory.
 *
 * Slabs are not freed while there is a pending callback, but instead are kept
 * on a deadlist, which is drained after the last callback completes. This means
 * that slabs are safe to access until kmem_move_end(), no matter how many of
 * their buffers have been freed. Once slab_refcnt reaches zero, it stays at
 * zero for as long as the slab remains on the deadlist and until the slab is
 * freed.
 */
static void
kmem_move_buffer(kmem_move_t *callback)
{
        kmem_cbrc_t response;
        kmem_slab_t *sp = callback->kmm_from_slab;
        kmem_cache_t *cp = sp->slab_cache;
        boolean_t free_on_slab;

        ASSERT(taskq_member(kmem_move_taskq, curthread));
        ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));
        ASSERT(KMEM_SLAB_MEMBER(sp, callback->kmm_from_buf));

        /*
         * The number of allocated buffers on the slab may have changed since we
         * last checked the slab's reclaimability (when the pending move was
         * enqueued), or the client may have responded NO when asked to move
         * another buffer on the same slab.
         */
        if (!kmem_slab_is_reclaimable(cp, sp, callback->kmm_flags)) {
                kmem_slab_free(cp, callback->kmm_to_buf);
                kmem_move_end(cp, callback);
                return;
        }

        /*
         * Checking the slab layer is easy, so we might as well do that here
         * in case we can avoid bothering the client.
         */
        mutex_enter(&cp->cache_lock);
        free_on_slab = (kmem_slab_allocated(cp, sp,
            callback->kmm_from_buf) == NULL);
        mutex_exit(&cp->cache_lock);

        if (free_on_slab) {
                kmem_slab_free(cp, callback->kmm_to_buf);
                kmem_move_end(cp, callback);
                return;
        }

        if (cp->cache_flags & KMF_BUFTAG) {
                /*
                 * Make kmem_cache_alloc_debug() apply the constructor for us.
                 */
                if (kmem_cache_alloc_debug(cp, callback->kmm_to_buf,
                    KM_NOSLEEP, 1, caller()) != 0) {
                        kmem_move_end(cp, callback);
                        return;
                }
        } else if (cp->cache_constructor != NULL &&
            cp->cache_constructor(callback->kmm_to_buf, cp->cache_private,
            KM_NOSLEEP) != 0) {
                atomic_inc_64(&cp->cache_alloc_fail);
                kmem_slab_free(cp, callback->kmm_to_buf);
                kmem_move_end(cp, callback);
                return;
        }

        cp->cache_defrag->kmd_callbacks++;
        cp->cache_defrag->kmd_thread = curthread;
        cp->cache_defrag->kmd_from_buf = callback->kmm_from_buf;
        cp->cache_defrag->kmd_to_buf = callback->kmm_to_buf;
        DTRACE_PROBE2(kmem__move__start, kmem_cache_t *, cp, kmem_move_t *,
            callback);

        response = cp->cache_move(callback->kmm_from_buf,
            callback->kmm_to_buf, cp->cache_bufsize, cp->cache_private);

        DTRACE_PROBE3(kmem__move__end, kmem_cache_t *, cp, kmem_move_t *,
            callback, kmem_cbrc_t, response);
        cp->cache_defrag->kmd_thread = NULL;
        cp->cache_defrag->kmd_from_buf = NULL;
        cp->cache_defrag->kmd_to_buf = NULL;

        if (response == KMEM_CBRC_YES) {
                cp->cache_defrag->kmd_yes++;
                kmem_slab_free_constructed(cp, callback->kmm_from_buf, B_FALSE);
                /* slab safe to access until kmem_move_end() */
                if (sp->slab_refcnt == 0)
                        cp->cache_defrag->kmd_slabs_freed++;
                mutex_enter(&cp->cache_lock);
                kmem_slab_move_yes(cp, sp, callback->kmm_from_buf);
                mutex_exit(&cp->cache_lock);
                kmem_move_end(cp, callback);
                return;
        }

        switch (response) {
        case KMEM_CBRC_NO:
                cp->cache_defrag->kmd_no++;
                mutex_enter(&cp->cache_lock);
                kmem_slab_move_no(cp, sp, callback->kmm_from_buf);
                mutex_exit(&cp->cache_lock);
                break;
        case KMEM_CBRC_LATER:
                cp->cache_defrag->kmd_later++;
                mutex_enter(&cp->cache_lock);
                if (!KMEM_SLAB_IS_PARTIAL(sp)) {
                        mutex_exit(&cp->cache_lock);
                        break;
                }

                if (++sp->slab_later_count >= KMEM_DISBELIEF) {
                        kmem_slab_move_no(cp, sp, callback->kmm_from_buf);
                } else if (!(sp->slab_flags & KMEM_SLAB_NOMOVE)) {
                        sp->slab_stuck_offset = KMEM_SLAB_OFFSET(sp,
                            callback->kmm_from_buf);
                }
                mutex_exit(&cp->cache_lock);
                break;
        case KMEM_CBRC_DONT_NEED:
                cp->cache_defrag->kmd_dont_need++;
                kmem_slab_free_constructed(cp, callback->kmm_from_buf, B_FALSE);
                if (sp->slab_refcnt == 0)
                        cp->cache_defrag->kmd_slabs_freed++;
                mutex_enter(&cp->cache_lock);
                kmem_slab_move_yes(cp, sp, callback->kmm_from_buf);
                mutex_exit(&cp->cache_lock);
                break;
        case KMEM_CBRC_DONT_KNOW:
                /*
                 * If we don't know if we can move this buffer or not, we'll
                 * just assume that we can't:  if the buffer is in fact free,
                 * then it is sitting in one of the per-CPU magazines or in
                 * a full magazine in the depot layer.  Either way, because
                 * defrag is induced in the same logic that reaps a cache,
                 * it's likely that full magazines will be returned to the
                 * system soon (thereby accomplishing what we're trying to
                 * accomplish here: return those magazines to their slabs).
                 * Given this, any work that we might do now to locate a buffer
                 * in a magazine is wasted (and expensive!) work; we bump
                 * a counter in this case and otherwise assume that we can't
                 * move it.
                 */
                cp->cache_defrag->kmd_dont_know++;
                break;
        default:
                panic("'%s' (%p) unexpected move callback response %d\n",
                    cp->cache_name, (void *)cp, response);
        }

        kmem_slab_free_constructed(cp, callback->kmm_to_buf, B_FALSE);
        kmem_move_end(cp, callback);
}

/* Return B_FALSE if there is insufficient memory for the move request. */
static boolean_t
kmem_move_begin(kmem_cache_t *cp, kmem_slab_t *sp, void *buf, int flags)
{
        void *to_buf;
        avl_index_t index;
        kmem_move_t *callback, *pending;
        ulong_t n;

        ASSERT(taskq_member(kmem_taskq, curthread));
        ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));
        ASSERT(sp->slab_flags & KMEM_SLAB_MOVE_PENDING);

        callback = kmem_cache_alloc(kmem_move_cache, KM_NOSLEEP);

        if (callback == NULL)
                return (B_FALSE);

        callback->kmm_from_slab = sp;
        callback->kmm_from_buf = buf;
        callback->kmm_flags = flags;

        mutex_enter(&cp->cache_lock);

        n = avl_numnodes(&cp->cache_partial_slabs);
        if ((n == 0) || ((n == 1) && !(flags & KMM_DEBUG))) {
                mutex_exit(&cp->cache_lock);
                kmem_cache_free(kmem_move_cache, callback);
                return (B_TRUE); /* there is no need for the move request */
        }

        pending = avl_find(&cp->cache_defrag->kmd_moves_pending, buf, &index);
        if (pending != NULL) {
                /*
                 * If the move is already pending and we're desperate now,
                 * update the move flags.
                 */
                if (flags & KMM_DESPERATE) {
                        pending->kmm_flags |= KMM_DESPERATE;
                }
                mutex_exit(&cp->cache_lock);
                kmem_cache_free(kmem_move_cache, callback);
                return (B_TRUE);
        }

        to_buf = kmem_slab_alloc_impl(cp, avl_first(&cp->cache_partial_slabs),
            B_FALSE);
        callback->kmm_to_buf = to_buf;
        avl_insert(&cp->cache_defrag->kmd_moves_pending, callback, index);

        mutex_exit(&cp->cache_lock);

        if (!taskq_dispatch(kmem_move_taskq, (task_func_t *)kmem_move_buffer,
            callback, TQ_NOSLEEP)) {
                mutex_enter(&cp->cache_lock);
                avl_remove(&cp->cache_defrag->kmd_moves_pending, callback);
                mutex_exit(&cp->cache_lock);
                kmem_slab_free(cp, to_buf);
                kmem_cache_free(kmem_move_cache, callback);
                return (B_FALSE);
        }

        return (B_TRUE);
}

static void
kmem_move_end(kmem_cache_t *cp, kmem_move_t *callback)
{
        avl_index_t index;

        ASSERT(cp->cache_defrag != NULL);
        ASSERT(taskq_member(kmem_move_taskq, curthread));
        ASSERT(MUTEX_NOT_HELD(&cp->cache_lock));

        mutex_enter(&cp->cache_lock);
        VERIFY(avl_find(&cp->cache_defrag->kmd_moves_pending,
            callback->kmm_from_buf, &index) != NULL);
        avl_remove(&cp->cache_defrag->kmd_moves_pending, callback);
        if (avl_is_empty(&cp->cache_defrag->kmd_moves_pending)) {
                list_t *deadlist = &cp->cache_defrag->kmd_deadlist;
                kmem_slab_t *sp;

                /*
                 * The last pending move completed. Release all slabs from the
                 * front of the dead list except for any slab at the tail that
                 * needs to be released from the context of kmem_move_buffers().
                 * kmem deferred unmapping the buffers on these slabs in order
                 * to guarantee that buffers passed to the move callback have
                 * been touched only by kmem or by the client itself.
                 */
                while ((sp = list_remove_head(deadlist)) != NULL) {
                        if (sp->slab_flags & KMEM_SLAB_MOVE_PENDING) {
                                list_insert_tail(deadlist, sp);
                                break;
                        }
                        cp->cache_defrag->kmd_deadcount--;
                        cp->cache_slab_destroy++;
                        mutex_exit(&cp->cache_lock);
                        kmem_slab_destroy(cp, sp);
                        mutex_enter(&cp->cache_lock);
                }
        }
        mutex_exit(&cp->cache_lock);
        kmem_cache_free(kmem_move_cache, callback);
}

/*
 * Move buffers from least used slabs first by scanning backwards from the end
 * of the partial slab list. Scan at most max_scan candidate slabs and move
 * buffers from at most max_slabs slabs (0 for all partial slabs in both cases).
 * If desperate to reclaim memory, move buffers from any partial slab, otherwise
 * skip slabs with a ratio of allocated buffers at or above the current
 * threshold. Return the number of unskipped slabs (at most max_slabs, -1 if the
 * scan is aborted) so that the caller can adjust the reclaimability threshold
 * depending on how many reclaimable slabs it finds.
 *
 * kmem_move_buffers() drops and reacquires cache_lock every time it issues a
 * move request, since it is not valid for kmem_move_begin() to call
 * kmem_cache_alloc() or taskq_dispatch() with cache_lock held.
 */
static int
kmem_move_buffers(kmem_cache_t *cp, size_t max_scan, size_t max_slabs,
    int flags)
{
        kmem_slab_t *sp;
        void *buf;
        int i, j; /* slab index, buffer index */
        int s; /* reclaimable slabs */
        int b; /* allocated (movable) buffers on reclaimable slab */
        boolean_t success;
        int refcnt;
        int nomove;

        ASSERT(taskq_member(kmem_taskq, curthread));
        ASSERT(MUTEX_HELD(&cp->cache_lock));
        ASSERT(kmem_move_cache != NULL);
        ASSERT(cp->cache_move != NULL && cp->cache_defrag != NULL);
        ASSERT((flags & KMM_DEBUG) ? !avl_is_empty(&cp->cache_partial_slabs) :
            avl_numnodes(&cp->cache_partial_slabs) > 1);

        if (kmem_move_blocked) {
                return (0);
        }

        if (kmem_move_fulltilt) {
                flags |= KMM_DESPERATE;
        }

        if (max_scan == 0 || (flags & KMM_DESPERATE)) {
                /*
                 * Scan as many slabs as needed to find the desired number of
                 * candidate slabs.
                 */
                max_scan = (size_t)-1;
        }

        if (max_slabs == 0 || (flags & KMM_DESPERATE)) {
                /* Find as many candidate slabs as possible. */
                max_slabs = (size_t)-1;
        }

        sp = avl_last(&cp->cache_partial_slabs);
        ASSERT(KMEM_SLAB_IS_PARTIAL(sp));
        for (i = 0, s = 0; (i < max_scan) && (s < max_slabs) && (sp != NULL) &&
            ((sp != avl_first(&cp->cache_partial_slabs)) ||
            (flags & KMM_DEBUG));
            sp = AVL_PREV(&cp->cache_partial_slabs, sp), i++) {

                if (!kmem_slab_is_reclaimable(cp, sp, flags)) {
                        continue;
                }
                s++;

                /* Look for allocated buffers to move. */
                for (j = 0, b = 0, buf = sp->slab_base;
                    (j < sp->slab_chunks) && (b < sp->slab_refcnt);
                    buf = (((char *)buf) + cp->cache_chunksize), j++) {

                        if (kmem_slab_allocated(cp, sp, buf) == NULL) {
                                continue;
                        }

                        b++;

                        /*
                         * Prevent the slab from being destroyed while we drop
                         * cache_lock and while the pending move is not yet
                         * registered. Flag the pending move while
                         * kmd_moves_pending may still be empty, since we can't
                         * yet rely on a non-zero pending move count to prevent
                         * the slab from being destroyed.
                         */
                        ASSERT(!(sp->slab_flags & KMEM_SLAB_MOVE_PENDING));
                        sp->slab_flags |= KMEM_SLAB_MOVE_PENDING;
                        /*
                         * Recheck refcnt and nomove after reacquiring the lock,
                         * since these control the order of partial slabs, and
                         * we want to know if we can pick up the scan where we
                         * left off.
                         */
                        refcnt = sp->slab_refcnt;
                        nomove = (sp->slab_flags & KMEM_SLAB_NOMOVE);
                        mutex_exit(&cp->cache_lock);

                        success = kmem_move_begin(cp, sp, buf, flags);

                        /*
                         * Now, before the lock is reacquired, kmem could
                         * process all pending move requests and purge the
                         * deadlist, so that upon reacquiring the lock, sp has
                         * been remapped. Or, the client may free all the
                         * objects on the slab while the pending moves are still
                         * on the taskq. Therefore, the KMEM_SLAB_MOVE_PENDING
                         * flag causes the slab to be put at the end of the
                         * deadlist and prevents it from being destroyed, since
                         * we plan to destroy it here after reacquiring the
                         * lock.
                         */
                        mutex_enter(&cp->cache_lock);
                        ASSERT(sp->slab_flags & KMEM_SLAB_MOVE_PENDING);
                        sp->slab_flags &= ~KMEM_SLAB_MOVE_PENDING;

                        if (sp->slab_refcnt == 0) {
                                list_t *deadlist =
                                    &cp->cache_defrag->kmd_deadlist;
                                list_remove(deadlist, sp);

                                if (!avl_is_empty(
                                    &cp->cache_defrag->kmd_moves_pending)) {
                                        /*
                                         * A pending move makes it unsafe to
                                         * destroy the slab, because even though
                                         * the move is no longer needed, the
                                         * context where that is determined
                                         * requires the slab to exist.
                                         * Fortunately, a pending move also
                                         * means we don't need to destroy the
                                         * slab here, since it will get
                                         * destroyed along with any other slabs
                                         * on the deadlist after the last
                                         * pending move completes.
                                         */
                                        list_insert_head(deadlist, sp);
                                        return (-1);
                                }

                                /*
                                 * Destroy the slab now if it was completely
                                 * freed while we dropped cache_lock and there
                                 * are no pending moves. Since slab_refcnt
                                 * cannot change once it reaches zero, no new
                                 * pending moves from that slab are possible.
                                 */
                                cp->cache_defrag->kmd_deadcount--;
                                cp->cache_slab_destroy++;
                                mutex_exit(&cp->cache_lock);
                                kmem_slab_destroy(cp, sp);
                                mutex_enter(&cp->cache_lock);
                                /*
                                 * Since we can't pick up the scan where we left
                                 * off, abort the scan and say nothing about the
                                 * number of reclaimable slabs.
                                 */
                                return (-1);
                        }

                        if (!success) {
                                /*
                                 * Abort the scan if there is not enough memory
                                 * for the request and say nothing about the
                                 * number of reclaimable slabs.
                                 */
                                return (-1);
                        }

                        /*
                         * The slab's position changed while the lock was
                         * dropped, so we don't know where we are in the
                         * sequence any more.
                         */
                        if (sp->slab_refcnt != refcnt) {
                                /*
                                 * If this is a KMM_DEBUG move, the slab_refcnt
                                 * may have changed because we allocated a
                                 * destination buffer on the same slab. In that
                                 * case, we're not interested in counting it.
                                 */
                                return (-1);
                        }
                        if ((sp->slab_flags & KMEM_SLAB_NOMOVE) != nomove)
                                return (-1);

                        /*
                         * Generating a move request allocates a destination
                         * buffer from the slab layer, bumping the first partial
                         * slab if it is completely allocated. If the current
                         * slab becomes the first partial slab as a result, we
                         * can't continue to scan backwards.
                         *
                         * If this is a KMM_DEBUG move and we allocated the
                         * destination buffer from the last partial slab, then
                         * the buffer we're moving is on the same slab and our
                         * slab_refcnt has changed, causing us to return before
                         * reaching here if there are no partial slabs left.
                         */
                        ASSERT(!avl_is_empty(&cp->cache_partial_slabs));
                        if (sp == avl_first(&cp->cache_partial_slabs)) {
                                /*
                                 * We're not interested in a second KMM_DEBUG
                                 * move.
                                 */
                                goto end_scan;
                        }
                }
        }
end_scan:

        return (s);
}

typedef struct kmem_move_notify_args {
        kmem_cache_t *kmna_cache;
        void *kmna_buf;
} kmem_move_notify_args_t;

static void
kmem_cache_move_notify_task(void *arg)
{
        kmem_move_notify_args_t *args = arg;
        kmem_cache_t *cp = args->kmna_cache;
        void *buf = args->kmna_buf;
        kmem_slab_t *sp;

        ASSERT(taskq_member(kmem_taskq, curthread));
        ASSERT(list_link_active(&cp->cache_link));

        kmem_free(args, sizeof (kmem_move_notify_args_t));
        mutex_enter(&cp->cache_lock);
        sp = kmem_slab_allocated(cp, NULL, buf);

        /* Ignore the notification if the buffer is no longer allocated. */
        if (sp == NULL) {
                mutex_exit(&cp->cache_lock);
                return;
        }

        /* Ignore the notification if there's no reason to move the buffer. */
        if (avl_numnodes(&cp->cache_partial_slabs) > 1) {
                /*
                 * So far the notification is not ignored. Ignore the
                 * notification if the slab is not marked by an earlier refusal
                 * to move a buffer.
                 */
                if (!(sp->slab_flags & KMEM_SLAB_NOMOVE) &&
                    (sp->slab_later_count == 0)) {
                        mutex_exit(&cp->cache_lock);
                        return;
                }

                kmem_slab_move_yes(cp, sp, buf);
                ASSERT(!(sp->slab_flags & KMEM_SLAB_MOVE_PENDING));
                sp->slab_flags |= KMEM_SLAB_MOVE_PENDING;
                mutex_exit(&cp->cache_lock);
                /* see kmem_move_buffers() about dropping the lock */
                (void) kmem_move_begin(cp, sp, buf, KMM_NOTIFY);
                mutex_enter(&cp->cache_lock);
                ASSERT(sp->slab_flags & KMEM_SLAB_MOVE_PENDING);
                sp->slab_flags &= ~KMEM_SLAB_MOVE_PENDING;
                if (sp->slab_refcnt == 0) {
                        list_t *deadlist = &cp->cache_defrag->kmd_deadlist;
                        list_remove(deadlist, sp);

                        if (!avl_is_empty(
                            &cp->cache_defrag->kmd_moves_pending)) {
                                list_insert_head(deadlist, sp);
                                mutex_exit(&cp->cache_lock);
                                return;
                        }

                        cp->cache_defrag->kmd_deadcount--;
                        cp->cache_slab_destroy++;
                        mutex_exit(&cp->cache_lock);
                        kmem_slab_destroy(cp, sp);
                        return;
                }
        } else {
                kmem_slab_move_yes(cp, sp, buf);
        }
        mutex_exit(&cp->cache_lock);
}

void
kmem_cache_move_notify(kmem_cache_t *cp, void *buf)
{
        kmem_move_notify_args_t *args;

        args = kmem_alloc(sizeof (kmem_move_notify_args_t), KM_NOSLEEP);
        if (args != NULL) {
                args->kmna_cache = cp;
                args->kmna_buf = buf;
                if (!taskq_dispatch(kmem_taskq,
                    (task_func_t *)kmem_cache_move_notify_task, args,
                    TQ_NOSLEEP))
                        kmem_free(args, sizeof (kmem_move_notify_args_t));
        }
}

static void
kmem_cache_defrag(kmem_cache_t *cp)
{
        size_t n;

        ASSERT(cp->cache_defrag != NULL);

        mutex_enter(&cp->cache_lock);
        n = avl_numnodes(&cp->cache_partial_slabs);
        if (n > 1) {
                /* kmem_move_buffers() drops and reacquires cache_lock */
                cp->cache_defrag->kmd_defrags++;
                (void) kmem_move_buffers(cp, n, 0, KMM_DESPERATE);
        }
        mutex_exit(&cp->cache_lock);
}

/* Is this cache above the fragmentation threshold? */
static boolean_t
kmem_cache_frag_threshold(kmem_cache_t *cp, uint64_t nfree)
{
        /*
         *      nfree           kmem_frag_numer
         * ------------------ > ---------------
         * cp->cache_buftotal   kmem_frag_denom
         */
        return ((nfree * kmem_frag_denom) >
            (cp->cache_buftotal * kmem_frag_numer));
}

static boolean_t
kmem_cache_is_fragmented(kmem_cache_t *cp, boolean_t *doreap)
{
        boolean_t fragmented;
        uint64_t nfree;

        ASSERT(MUTEX_HELD(&cp->cache_lock));
        *doreap = B_FALSE;

        if (kmem_move_fulltilt) {
                if (avl_numnodes(&cp->cache_partial_slabs) > 1) {
                        return (B_TRUE);
                }
        } else {
                if ((cp->cache_complete_slab_count + avl_numnodes(
                    &cp->cache_partial_slabs)) < kmem_frag_minslabs) {
                        return (B_FALSE);
                }
        }

        nfree = cp->cache_bufslab;
        fragmented = ((avl_numnodes(&cp->cache_partial_slabs) > 1) &&
            kmem_cache_frag_threshold(cp, nfree));

        /*
         * Free buffers in the magazine layer appear allocated from the point of
         * view of the slab layer. We want to know if the slab layer would
         * appear fragmented if we included free buffers from magazines that
         * have fallen out of the working set.
         */
        if (!fragmented) {
                long reap;

                mutex_enter(&cp->cache_depot_lock);
                reap = MIN(cp->cache_full.ml_reaplimit, cp->cache_full.ml_min);
                reap = MIN(reap, cp->cache_full.ml_total);
                mutex_exit(&cp->cache_depot_lock);

                nfree += ((uint64_t)reap * cp->cache_magtype->mt_magsize);
                if (kmem_cache_frag_threshold(cp, nfree)) {
                        *doreap = B_TRUE;
                }
        }

        return (fragmented);
}

/* Called periodically from kmem_taskq */
static void
kmem_cache_scan(kmem_cache_t *cp)
{
        boolean_t reap = B_FALSE;
        kmem_defrag_t *kmd;

        ASSERT(taskq_member(kmem_taskq, curthread));

        mutex_enter(&cp->cache_lock);

        kmd = cp->cache_defrag;
        if (kmd->kmd_consolidate > 0) {
                kmd->kmd_consolidate--;
                mutex_exit(&cp->cache_lock);
                kmem_cache_reap(cp);
                return;
        }

        if (kmem_cache_is_fragmented(cp, &reap)) {
                size_t slabs_found;

                /*
                 * Consolidate reclaimable slabs from the end of the partial
                 * slab list (scan at most kmem_reclaim_scan_range slabs to find
                 * reclaimable slabs). Keep track of how many candidate slabs we
                 * looked for and how many we actually found so we can adjust
                 * the definition of a candidate slab if we're having trouble
                 * finding them.
                 *
                 * kmem_move_buffers() drops and reacquires cache_lock.
                 */
                kmd->kmd_scans++;
                slabs_found = kmem_move_buffers(cp, kmem_reclaim_scan_range,
                    kmem_reclaim_max_slabs, 0);
                if (slabs_found >= 0) {
                        kmd->kmd_slabs_sought += kmem_reclaim_max_slabs;
                        kmd->kmd_slabs_found += slabs_found;
                }

                if (++kmd->kmd_tries >= kmem_reclaim_scan_range) {
                        kmd->kmd_tries = 0;

                        /*
                         * If we had difficulty finding candidate slabs in
                         * previous scans, adjust the threshold so that
                         * candidates are easier to find.
                         */
                        if (kmd->kmd_slabs_found == kmd->kmd_slabs_sought) {
                                kmem_adjust_reclaim_threshold(kmd, -1);
                        } else if ((kmd->kmd_slabs_found * 2) <
                            kmd->kmd_slabs_sought) {
                                kmem_adjust_reclaim_threshold(kmd, 1);
                        }
                        kmd->kmd_slabs_sought = 0;
                        kmd->kmd_slabs_found = 0;
                }
        } else {
                kmem_reset_reclaim_threshold(cp->cache_defrag);
#ifdef  DEBUG
                if (!avl_is_empty(&cp->cache_partial_slabs)) {
                        /*
                         * In a debug kernel we want the consolidator to
                         * run occasionally even when there is plenty of
                         * memory.
                         */
                        uint16_t debug_rand;

                        (void) random_get_bytes((uint8_t *)&debug_rand, 2);
                        if (!kmem_move_noreap &&
                            ((debug_rand % kmem_mtb_reap) == 0)) {
                                mutex_exit(&cp->cache_lock);
                                kmem_cache_reap(cp);
                                return;
                        } else if ((debug_rand % kmem_mtb_move) == 0) {
                                kmd->kmd_scans++;
                                (void) kmem_move_buffers(cp,
                                    kmem_reclaim_scan_range, 1, KMM_DEBUG);
                        }
                }
#endif  /* DEBUG */
        }

        mutex_exit(&cp->cache_lock);

        if (reap)
                kmem_depot_ws_reap(cp);
}