mm/slob.c

   1 /*
   2  * SLOB Allocator: Simple List Of Blocks
   3  *
   4  * Matt Mackall <mpm@selenic.com> 12/30/03
   5  *
   6  * NUMA support by Paul Mundt, 2007.
   7  *
   8  * How SLOB works:
   9  *
  10  * The core of SLOB is a traditional K&R style heap allocator, with
  11  * support for returning aligned objects. The granularity of this
  12  * allocator is as little as 2 bytes, however typically most architectures
  13  * will require 4 bytes on 32-bit and 8 bytes on 64-bit.
  14  *
  15  * The slob heap is a set of linked list of pages from alloc_pages(),
  16  * and within each page, there is a singly-linked list of free blocks
  17  * (slob_t). The heap is grown on demand. To reduce fragmentation,
  18  * heap pages are segregated into three lists, with objects less than
  19  * 256 bytes, objects less than 1024 bytes, and all other objects.
  20  *
  21  * Allocation from heap involves first searching for a page with
  22  * sufficient free blocks (using a next-fit-like approach) followed by
  23  * a first-fit scan of the page. Deallocation inserts objects back
  24  * into the free list in address order, so this is effectively an
  25  * address-ordered first fit.
  26  *
  27  * Above this is an implementation of kmalloc/kfree. Blocks returned
  28  * from kmalloc are prepended with a 4-byte header with the kmalloc size.
  29  * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
  30  * alloc_pages() directly, allocating compound pages so the page order
  31  * does not have to be separately tracked, and also stores the exact
  32  * allocation size in page->private so that it can be used to accurately
  33  * provide ksize(). These objects are detected in kfree() because slob_page()
  34  * is false for them.
  35  *
  36  * SLAB is emulated on top of SLOB by simply calling constructors and
  37  * destructors for every SLAB allocation. Objects are returned with the
  38  * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which
  39  * case the low-level allocator will fragment blocks to create the proper
  40  * alignment. Again, objects of page-size or greater are allocated by
  41  * calling alloc_pages(). As SLAB objects know their size, no separate
  42  * size bookkeeping is necessary and there is essentially no allocation
  43  * space overhead, and compound pages aren't needed for multi-page
  44  * allocations.
  45  *
  46  * NUMA support in SLOB is fairly simplistic, pushing most of the real
  47  * logic down to the page allocator, and simply doing the node accounting
  48  * on the upper levels. In the event that a node id is explicitly
  49  * provided, alloc_pages_exact_node() with the specified node id is used
  50  * instead. The common case (or when the node id isn't explicitly provided)
  51  * will default to the current node, as per numa_node_id().
  52  *
  53  * Node aware pages are still inserted in to the global freelist, and
  54  * these are scanned for by matching against the node id encoded in the
  55  * page flags. As a result, block allocations that can be satisfied from
  56  * the freelist will only be done so on pages residing on the same node,
  57  * in order to prevent random node placement.
  58  */
  59
  60 #include <linux/kernel.h>
  61 #include <linux/slab.h>
  62 #include "slab.h"
  63
  64 #include <linux/mm.h>
  65 #include <linux/swap.h> /* struct reclaim_state */
  66 #include <linux/cache.h>
  67 #include <linux/init.h>
  68 #include <linux/export.h>
  69 #include <linux/rcupdate.h>
  70 #include <linux/list.h>
  71 #include <linux/kmemleak.h>
  72
  73 #include <trace/events/kmem.h>
  74
  75 #include <linux/atomic.h>
  76
  77 /*
  78  * slob_block has a field 'units', which indicates size of block if +ve,
  79  * or offset of next block if -ve (in SLOB_UNITs).
  80  *
  81  * Free blocks of size 1 unit simply contain the offset of the next block.
  82  * Those with larger size contain their size in the first SLOB_UNIT of
  83  * memory, and the offset of the next free block in the second SLOB_UNIT.
  84  */
  85 #if PAGE_SIZE <= (32767 * 2)
  86 typedef s16 slobidx_t;
  87 #else
  88 typedef s32 slobidx_t;
  89 #endif
  90
  91 struct slob_block {
  92         slobidx_t units;
  93 };
  94 typedef struct slob_block slob_t;
  95
  96 /*
  97  * All partially free slob pages go on these lists.
  98  */
  99 #define SLOB_BREAK1 256
 100 #define SLOB_BREAK2 1024
 101 static LIST_HEAD(free_slob_small);
 102 static LIST_HEAD(free_slob_medium);
 103 static LIST_HEAD(free_slob_large);
 104
 105 /*
 106  * slob_page_free: true for pages on free_slob_pages list.
 107  */
 108 static inline int slob_page_free(struct page *sp)
 109 {
 110         return PageSlobFree(sp);
 111 }
 112
 113 static void set_slob_page_free(struct page *sp, struct list_head *list)
 114 {
 115         list_add(&sp->list, list);
 116         __SetPageSlobFree(sp);
 117 }
 118
 119 static inline void clear_slob_page_free(struct page *sp)
 120 {
 121         list_del(&sp->list);
 122         __ClearPageSlobFree(sp);
 123 }
 124
 125 #define SLOB_UNIT sizeof(slob_t)
 126 #define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
 127 #define SLOB_ALIGN L1_CACHE_BYTES
 128
 129 /*
 130  * struct slob_rcu is inserted at the tail of allocated slob blocks, which
 131  * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
 132  * the block using call_rcu.
 133  */
 134 struct slob_rcu {
 135         struct rcu_head head;
 136         int size;
 137 };
 138
 139 /*
 140  * slob_lock protects all slob allocator structures.
 141  */
 142 static DEFINE_SPINLOCK(slob_lock);
 143
 144 /*
 145  * Encode the given size and next info into a free slob block s.
 146  */
 147 static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
 148 {
 149         slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
 150         slobidx_t offset = next - base;
 151
 152         if (size > 1) {
 153                 s[0].units = size;
 154                 s[1].units = offset;
 155         } else
 156                 s[0].units = -offset;
 157 }
 158
 159 /*
 160  * Return the size of a slob block.
 161  */
 162 static slobidx_t slob_units(slob_t *s)
 163 {
 164         if (s->units > 0)
 165                 return s->units;
 166         return 1;
 167 }
 168
 169 /*
 170  * Return the next free slob block pointer after this one.
 171  */
 172 static slob_t *slob_next(slob_t *s)
 173 {
 174         slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
 175         slobidx_t next;
 176
 177         if (s[0].units < 0)
 178                 next = -s[0].units;
 179         else
 180                 next = s[1].units;
 181         return base+next;
 182 }
 183
 184 /*
 185  * Returns true if s is the last free block in its page.
 186  */
 187 static int slob_last(slob_t *s)
 188 {
 189         return !((unsigned long)slob_next(s) & ~PAGE_MASK);
 190 }
 191
 192 static void *slob_new_pages(gfp_t gfp, int order, int node)
 193 {
 194         void *page;
 195
 196 #ifdef CONFIG_NUMA
 197         if (node != NUMA_NO_NODE)
 198                 page = alloc_pages_exact_node(node, gfp, order);
 199         else
 200 #endif
 201                 page = alloc_pages(gfp, order);
 202
 203         if (!page)
 204                 return NULL;
 205
 206         return page_address(page);
 207 }
 208
 209 static void slob_free_pages(void *b, int order)
 210 {
 211         if (current->reclaim_state)
 212                 current->reclaim_state->reclaimed_slab += 1 << order;
 213         free_pages((unsigned long)b, order);
 214 }
 215
 216 /*
 217  * Allocate a slob block within a given slob_page sp.
 218  */
 219 static void *slob_page_alloc(struct page *sp, size_t size, int align)
 220 {
 221         slob_t *prev, *cur, *aligned = NULL;
 222         int delta = 0, units = SLOB_UNITS(size);
 223
 224         for (prev = NULL, cur = sp->freelist; ; prev = cur, cur = slob_next(cur)) {
 225                 slobidx_t avail = slob_units(cur);
 226
 227                 if (align) {
 228                         aligned = (slob_t *)ALIGN((unsigned long)cur, align);
 229                         delta = aligned - cur;
 230                 }
 231                 if (avail >= units + delta) { /* room enough? */
 232                         slob_t *next;
 233
 234                         if (delta) { /* need to fragment head to align? */
 235                                 next = slob_next(cur);
 236                                 set_slob(aligned, avail - delta, next);
 237                                 set_slob(cur, delta, aligned);
 238                                 prev = cur;
 239                                 cur = aligned;
 240                                 avail = slob_units(cur);
 241                         }
 242
 243                         next = slob_next(cur);
 244                         if (avail == units) { /* exact fit? unlink. */
 245                                 if (prev)
 246                                         set_slob(prev, slob_units(prev), next);
 247                                 else
 248                                         sp->freelist = next;
 249                         } else { /* fragment */
 250                                 if (prev)
 251                                         set_slob(prev, slob_units(prev), cur + units);
 252                                 else
 253                                         sp->freelist = cur + units;
 254                                 set_slob(cur + units, avail - units, next);
 255                         }
 256
 257                         sp->units -= units;
 258                         if (!sp->units)
 259                                 clear_slob_page_free(sp);
 260                         return cur;
 261                 }
 262                 if (slob_last(cur))
 263                         return NULL;
 264         }
 265 }
 266
 267 /*
 268  * slob_alloc: entry point into the slob allocator.
 269  */
 270 static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
 271 {
 272         struct page *sp;
 273         struct list_head *prev;
 274         struct list_head *slob_list;
 275         slob_t *b = NULL;
 276         unsigned long flags;
 277
 278         if (size < SLOB_BREAK1)
 279                 slob_list = &free_slob_small;
 280         else if (size < SLOB_BREAK2)
 281                 slob_list = &free_slob_medium;
 282         else
 283                 slob_list = &free_slob_large;
 284
 285         spin_lock_irqsave(&slob_lock, flags);
 286         /* Iterate through each partially free page, try to find room */
 287         list_for_each_entry(sp, slob_list, list) {
 288 #ifdef CONFIG_NUMA
 289                 /*
 290                  * If there's a node specification, search for a partial
 291                  * page with a matching node id in the freelist.
 292                  */
 293                 if (node != NUMA_NO_NODE && page_to_nid(sp) != node)
 294                         continue;
 295 #endif
 296                 /* Enough room on this page? */
 297                 if (sp->units < SLOB_UNITS(size))
 298                         continue;
 299
 300                 /* Attempt to alloc */
 301                 prev = sp->list.prev;
 302                 b = slob_page_alloc(sp, size, align);
 303                 if (!b)
 304                         continue;
 305
 306                 /* Improve fragment distribution and reduce our average
 307                  * search time by starting our next search here. (see
 308                  * Knuth vol 1, sec 2.5, pg 449) */
 309                 if (prev != slob_list->prev &&
 310                                 slob_list->next != prev->next)
 311                         list_move_tail(slob_list, prev->next);
 312                 break;
 313         }
 314         spin_unlock_irqrestore(&slob_lock, flags);
 315
 316         /* Not enough space: must allocate a new page */
 317         if (!b) {
 318                 b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node);
 319                 if (!b)
 320                         return NULL;
 321                 sp = virt_to_page(b);
 322                 __SetPageSlab(sp);
 323
 324                 spin_lock_irqsave(&slob_lock, flags);
 325                 sp->units = SLOB_UNITS(PAGE_SIZE);
 326                 sp->freelist = b;
 327                 INIT_LIST_HEAD(&sp->list);
 328                 set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
 329                 set_slob_page_free(sp, slob_list);
 330                 b = slob_page_alloc(sp, size, align);
 331                 BUG_ON(!b);
 332                 spin_unlock_irqrestore(&slob_lock, flags);
 333         }
 334         if (unlikely((gfp & __GFP_ZERO) && b))
 335                 memset(b, 0, size);
 336         return b;
 337 }
 338
 339 /*
 340  * slob_free: entry point into the slob allocator.
 341  */
 342 static void slob_free(void *block, int size)
 343 {
 344         struct page *sp;
 345         slob_t *prev, *next, *b = (slob_t *)block;
 346         slobidx_t units;
 347         unsigned long flags;
 348         struct list_head *slob_list;
 349
 350         if (unlikely(ZERO_OR_NULL_PTR(block)))
 351                 return;
 352         BUG_ON(!size);
 353
 354         sp = virt_to_page(block);
 355         units = SLOB_UNITS(size);
 356
 357         spin_lock_irqsave(&slob_lock, flags);
 358
 359         if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
 360                 /* Go directly to page allocator. Do not pass slob allocator */
 361                 if (slob_page_free(sp))
 362                         clear_slob_page_free(sp);
 363                 spin_unlock_irqrestore(&slob_lock, flags);
 364                 __ClearPageSlab(sp);
 365                 reset_page_mapcount(sp);
 366                 slob_free_pages(b, 0);
 367                 return;
 368         }
 369
 370         if (!slob_page_free(sp)) {
 371                 /* This slob page is about to become partially free. Easy! */
 372                 sp->units = units;
 373                 sp->freelist = b;
 374                 set_slob(b, units,
 375                         (void *)((unsigned long)(b +
 376                                         SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
 377                 if (size < SLOB_BREAK1)
 378                         slob_list = &free_slob_small;
 379                 else if (size < SLOB_BREAK2)
 380                         slob_list = &free_slob_medium;
 381                 else
 382                         slob_list = &free_slob_large;
 383                 set_slob_page_free(sp, slob_list);
 384                 goto out;
 385         }
 386
 387         /*
 388          * Otherwise the page is already partially free, so find reinsertion
 389          * point.
 390          */
 391         sp->units += units;
 392
 393         if (b < (slob_t *)sp->freelist) {
 394                 if (b + units == sp->freelist) {
 395                         units += slob_units(sp->freelist);
 396                         sp->freelist = slob_next(sp->freelist);
 397                 }
 398                 set_slob(b, units, sp->freelist);
 399                 sp->freelist = b;
 400         } else {
 401                 prev = sp->freelist;
 402                 next = slob_next(prev);
 403                 while (b > next) {
 404                         prev = next;
 405                         next = slob_next(prev);
 406                 }
 407
 408                 if (!slob_last(prev) && b + units == next) {
 409                         units += slob_units(next);
 410                         set_slob(b, units, slob_next(next));
 411                 } else
 412                         set_slob(b, units, next);
 413
 414                 if (prev + slob_units(prev) == b) {
 415                         units = slob_units(b) + slob_units(prev);
 416                         set_slob(prev, units, slob_next(b));
 417                 } else
 418                         set_slob(prev, slob_units(prev), b);
 419         }
 420 out:
 421         spin_unlock_irqrestore(&slob_lock, flags);
 422 }
 423
 424 /*
 425  * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
 426  */
 427
 428 static __always_inline void *
 429 __do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller)
 430 {
 431         unsigned int *m;
 432         int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
 433         void *ret;
 434
 435         gfp &= gfp_allowed_mask;
 436
 437         lockdep_trace_alloc(gfp);
 438
 439         if (size < PAGE_SIZE - align) {
 440                 if (!size)
 441                         return ZERO_SIZE_PTR;
 442
 443                 m = slob_alloc(size + align, gfp, align, node);
 444
 445                 if (!m)
 446                         return NULL;
 447                 *m = size;
 448                 ret = (void *)m + align;
 449
 450                 trace_kmalloc_node(caller, ret,
 451                                    size, size + align, gfp, node);
 452         } else {
 453                 unsigned int order = get_order(size);
 454
 455                 if (likely(order))
 456                         gfp |= __GFP_COMP;
 457                 ret = slob_new_pages(gfp, order, node);
 458                 if (ret) {
 459                         struct page *page;
 460                         page = virt_to_page(ret);
 461                         page->private = size;
 462                 }
 463
 464                 trace_kmalloc_node(caller, ret,
 465                                    size, PAGE_SIZE << order, gfp, node);
 466         }
 467
 468         kmemleak_alloc(ret, size, 1, gfp);
 469         return ret;
 470 }
 471
 472 void *__kmalloc_node(size_t size, gfp_t gfp, int node)
 473 {
 474         return __do_kmalloc_node(size, gfp, node, _RET_IP_);
 475 }
 476 EXPORT_SYMBOL(__kmalloc_node);
 477
 478 #ifdef CONFIG_TRACING
 479 void *__kmalloc_track_caller(size_t size, gfp_t gfp, unsigned long caller)
 480 {
 481         return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, caller);
 482 }
 483
 484 #ifdef CONFIG_NUMA
 485 void *__kmalloc_node_track_caller(size_t size, gfp_t gfp,
 486                                         int node, unsigned long caller)
 487 {
 488         return __do_kmalloc_node(size, gfp, node, caller);
 489 }
 490 #endif
 491 #endif
 492
 493 void kfree(const void *block)
 494 {
 495         struct page *sp;
 496
 497         trace_kfree(_RET_IP_, block);
 498
 499         if (unlikely(ZERO_OR_NULL_PTR(block)))
 500                 return;
 501         kmemleak_free(block);
 502
 503         sp = virt_to_page(block);
 504         if (PageSlab(sp)) {
 505                 int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
 506                 unsigned int *m = (unsigned int *)(block - align);
 507                 slob_free(m, *m + align);
 508         } else
 509                 put_page(sp);
 510 }
 511 EXPORT_SYMBOL(kfree);
 512
 513 /* can't use ksize for kmem_cache_alloc memory, only kmalloc */
 514 size_t ksize(const void *block)
 515 {
 516         struct page *sp;
 517
 518         BUG_ON(!block);
 519         if (unlikely(block == ZERO_SIZE_PTR))
 520                 return 0;
 521
 522         sp = virt_to_page(block);
 523         if (PageSlab(sp)) {
 524                 int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
 525                 unsigned int *m = (unsigned int *)(block - align);
 526                 return SLOB_UNITS(*m) * SLOB_UNIT;
 527         } else
 528                 return sp->private;
 529 }
 530 EXPORT_SYMBOL(ksize);
 531
 532 int __kmem_cache_create(struct kmem_cache *c, unsigned long flags)
 533 {
 534         size_t align = c->size;
 535
 536         if (flags & SLAB_DESTROY_BY_RCU) {
 537                 /* leave room for rcu footer at the end of object */
 538                 c->size += sizeof(struct slob_rcu);
 539         }
 540         c->flags = flags;
 541         /* ignore alignment unless it's forced */
 542         c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
 543         if (c->align < ARCH_SLAB_MINALIGN)
 544                 c->align = ARCH_SLAB_MINALIGN;
 545         if (c->align < align)
 546                 c->align = align;
 547
 548         return 0;
 549 }
 550
 551 void *kmem_cache_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
 552 {
 553         void *b;
 554
 555         flags &= gfp_allowed_mask;
 556
 557         lockdep_trace_alloc(flags);
 558
 559         if (c->size < PAGE_SIZE) {
 560                 b = slob_alloc(c->size, flags, c->align, node);
 561                 trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
 562                                             SLOB_UNITS(c->size) * SLOB_UNIT,
 563                                             flags, node);
 564         } else {
 565                 b = slob_new_pages(flags, get_order(c->size), node);
 566                 trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
 567                                             PAGE_SIZE << get_order(c->size),
 568                                             flags, node);
 569         }
 570
 571         if (c->ctor)
 572                 c->ctor(b);
 573
 574         kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
 575         return b;
 576 }
 577 EXPORT_SYMBOL(kmem_cache_alloc_node);
 578
 579 static void __kmem_cache_free(void *b, int size)
 580 {
 581         if (size < PAGE_SIZE)
 582                 slob_free(b, size);
 583         else
 584                 slob_free_pages(b, get_order(size));
 585 }
 586
 587 static void kmem_rcu_free(struct rcu_head *head)
 588 {
 589         struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
 590         void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
 591
 592         __kmem_cache_free(b, slob_rcu->size);
 593 }
 594
 595 void kmem_cache_free(struct kmem_cache *c, void *b)
 596 {
 597         kmemleak_free_recursive(b, c->flags);
 598         if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) {
 599                 struct slob_rcu *slob_rcu;
 600                 slob_rcu = b + (c->size - sizeof(struct slob_rcu));
 601                 slob_rcu->size = c->size;
 602                 call_rcu(&slob_rcu->head, kmem_rcu_free);
 603         } else {
 604                 __kmem_cache_free(b, c->size);
 605         }
 606
 607         trace_kmem_cache_free(_RET_IP_, b);
 608 }
 609 EXPORT_SYMBOL(kmem_cache_free);
 610
 611 unsigned int kmem_cache_size(struct kmem_cache *c)
 612 {
 613         return c->size;
 614 }
 615 EXPORT_SYMBOL(kmem_cache_size);
 616
 617 int __kmem_cache_shutdown(struct kmem_cache *c)
 618 {
 619         /* No way to check for remaining objects */
 620         return 0;
 621 }
 622
 623 int kmem_cache_shrink(struct kmem_cache *d)
 624 {
 625         return 0;
 626 }
 627 EXPORT_SYMBOL(kmem_cache_shrink);
 628
 629 struct kmem_cache kmem_cache_boot = {
 630         .name = "kmem_cache",
 631         .size = sizeof(struct kmem_cache),
 632         .flags = SLAB_PANIC,
 633         .align = ARCH_KMALLOC_MINALIGN,
 634 };
 635
 636 void __init kmem_cache_init(void)
 637 {
 638         kmem_cache = &kmem_cache_boot;
 639         slab_state = UP;
 640 }
 641
 642 void __init kmem_cache_init_late(void)
 643 {
 644         slab_state = FULL;
 645 }