2 * Copyright (c) 2004 Poul-Henning Kamp
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * $FreeBSD: src/sys/kern/subr_unit.c,v 1.7 2005/03/14 06:51:29 phk Exp $
29 * Unit number allocation functions.
31 * These functions implement a mixed run-length/bitmap management of unit
32 * number spaces in a very memory efficient manner.
34 * Allocation policy is always lowest free number first.
36 * A return value of -1 signals that no more unit numbers are available.
38 * There is no cost associated with the range of unitnumbers, so unless
39 * the resource really is finite, specify INT_MAX to new_unrhdr() and
40 * forget about checking the return value.
42 * If a mutex is not provided when the unit number space is created, a
43 * default global mutex is used. The advantage to passing a mutex in, is
44 * that the the alloc_unrl() function can be called with the mutex already
45 * held (it will not be released by alloc_unrl()).
47 * The allocation function alloc_unr{l}() never sleeps (but it may block on
48 * the mutex of course).
50 * Freeing a unit number may require allocating memory, and can therefore
51 * sleep so the free_unr() function does not come in a pre-locked variant.
53 * A userland test program is included.
55 * Memory usage is a very complex function of the the exact allocation
56 * pattern, but always very compact:
57 * * For the very typical case where a single unbroken run of unit
58 * numbers are allocated 44 bytes are used on x86.
59 * * For a unit number space of 1000 units and the random pattern
60 * in the usermode test program included, the worst case usage
61 * was 252 bytes on x86 for 500 allocated and 500 free units.
62 * * For a unit number space of 10000 units and the random pattern
63 * in the usermode test program included, the worst case usage
64 * was 798 bytes on x86 for 5000 allocated and 5000 free units.
65 * * The worst case is where every other unit number is allocated and
66 * the the rest are free. In that case 44 + N/4 bytes are used where
67 * N is the number of the highest unit allocated.
70 #include <sys/types.h>
71 #include <sys/queue.h>
72 #include <sys/bitstring.h>
76 #include <sys/param.h>
77 #include <sys/malloc.h>
78 #include <sys/kernel.h>
79 #include <sys/systm.h>
80 #include <sys/limits.h>
85 * In theory it would be smarter to allocate the individual blocks
86 * with the zone allocator, but at this time the expectation is that
87 * there will typically not even be enough allocations to fill a single
88 * page, so we stick with malloc for now.
90 static MALLOC_DEFINE(M_UNIT
, "Unitno", "Unit number allocation");
92 #define Malloc(foo) kmalloc(foo, M_UNIT, M_WAITOK | M_ZERO)
93 #define Free(foo) kfree(foo, M_UNIT)
95 static struct lock unit_lock
;
97 LOCK_SYSINIT(unit
, &unit_lock
, "unit# allocation", LK_CANRECURSE
);
99 #else /* ...USERLAND */
101 /* No unit allocation on DragonFly's userland */
103 #endif /* USERLAND */
106 * This is our basic building block.
108 * It can be used in three different ways depending on the value of the ptr
110 * If ptr is NULL, it represents a run of free items.
111 * If ptr points to the unrhdr it represents a run of allocated items.
112 * Otherwise it points to an bitstring of allocated items.
114 * For runs the len field is the length of the run.
115 * For bitmaps the len field represents the number of allocated items.
117 * The bitmap is the same size as struct unr to optimize memory management.
120 TAILQ_ENTRY(unr
) list
;
127 bitstr_t map
[sizeof(struct unr
) - 1];
130 CTASSERT(sizeof(struct unr
) == sizeof(struct unrb
));
132 /* Number of bits in the bitmap */
133 #define NBITS ((int)sizeof(((struct unrb *)NULL)->map) * 8)
135 /* Header element for a unr number space. */
138 TAILQ_HEAD(unrhd
,unr
) head
;
139 u_int low
; /* Lowest item */
140 u_int high
; /* Highest item */
141 u_int busy
; /* Count of allocated items */
142 u_int alloc
; /* Count of memory allocations */
143 u_int first
; /* items in allocated from start */
144 u_int last
; /* items free at end */
149 #if defined(DIAGNOSTIC) || !defined(_KERNEL)
151 * Consistency check function.
153 * Checks the internal consistency as well as we can.
155 * Called at all boundaries of this API.
158 check_unrhdr(struct unrhdr
*uh
, int line
)
166 TAILQ_FOREACH(up
, &uh
->head
, list
) {
168 if (up
->ptr
!= uh
&& up
->ptr
!= NULL
) {
170 KASSERT (up
->len
<= NBITS
,
171 ("UNR inconsistency: len %u max %d (line %d)\n",
172 up
->len
, NBITS
, line
));
175 for (x
= 0; x
< up
->len
; x
++)
176 if (bit_test(ub
->map
, x
))
178 KASSERT (w
== ub
->busy
,
179 ("UNR inconsistency: busy %u found %u (line %d)\n",
182 } else if (up
->ptr
!= NULL
)
185 KASSERT (y
== uh
->busy
,
186 ("UNR inconsistency: items %u found %u (line %d)\n",
188 KASSERT (z
== uh
->alloc
,
189 ("UNR inconsistency: chunks %u found %u (line %d)\n",
190 uh
->alloc
, z
, line
));
196 check_unrhdr(struct unrhdr
*uh
, int line
)
205 * Userland memory management. Just use calloc and keep track of how
206 * many elements we have allocated for check_unrhdr().
209 static __inline
void *
210 new_unr(struct unrhdr
*uh
, void **p1
, void **p2
)
215 KASSERT(*p1
!= NULL
|| *p2
!= NULL
, ("Out of cached memory"));
228 delete_unr(struct unrhdr
*uh
, void *ptr
)
236 * Allocate a new unrheader set.
238 * Highest and lowest valid values given as paramters.
242 new_unrhdr(int low
, int high
, struct lock
*lock
)
247 ("UNR: use error: new_unrhdr(%u, %u)", low
, high
));
248 uh
= Malloc(sizeof *uh
);
252 uh
->lock
= &unit_lock
;
253 TAILQ_INIT(&uh
->head
);
257 uh
->last
= 1 + (high
- low
);
258 check_unrhdr(uh
, __LINE__
);
263 delete_unrhdr(struct unrhdr
*uh
)
266 check_unrhdr(uh
, __LINE__
);
267 KASSERT(uh
->busy
== 0, ("unrhdr has %u allocations", uh
->busy
));
268 KASSERT(uh
->alloc
== 0, ("UNR memory leak in delete_unrhdr"));
273 is_bitmap(struct unrhdr
*uh
, struct unr
*up
)
275 return (up
->ptr
!= uh
&& up
->ptr
!= NULL
);
279 * Look for sequence of items which can be combined into a bitmap, if
280 * multiple are present, take the one which saves most memory.
282 * Return (1) if a sequence was found to indicate that another call
283 * might be able to do more. Return (0) if we found no suitable sequence.
285 * NB: called from alloc_unr(), no new memory allocation allowed.
288 optimize_unr(struct unrhdr
*uh
)
290 struct unr
*up
, *uf
, *us
;
291 struct unrb
*ub
, *ubf
;
295 * Look for the run of items (if any) which when collapsed into
296 * a bitmap would save most memory.
300 TAILQ_FOREACH(uf
, &uh
->head
, list
) {
301 if (uf
->len
>= NBITS
)
304 if (is_bitmap(uh
, uf
))
309 up
= TAILQ_NEXT(up
, list
);
312 if ((up
->len
+ l
) > NBITS
)
315 if (is_bitmap(uh
, up
))
328 * If the first element is not a bitmap, make it one.
329 * Trying to do so without allocating more memory complicates things
332 if (!is_bitmap(uh
, us
)) {
333 uf
= TAILQ_NEXT(us
, list
);
334 TAILQ_REMOVE(&uh
->head
, us
, list
);
336 l
= us
->ptr
== uh
? 1 : 0;
340 bit_nset(ub
->map
, 0, a
);
343 bit_nclear(ub
->map
, 0, a
);
345 if (!is_bitmap(uh
, uf
)) {
346 if (uf
->ptr
== NULL
) {
347 bit_nclear(ub
->map
, a
, a
+ uf
->len
- 1);
349 bit_nset(ub
->map
, a
, a
+ uf
->len
- 1);
357 for (l
= 0; l
< uf
->len
; l
++, a
++) {
358 if (bit_test(ubf
->map
, l
)) {
362 bit_clear(ub
->map
, a
);
366 delete_unr(uh
, uf
->ptr
);
373 uf
= TAILQ_NEXT(us
, list
);
376 if (uf
->len
+ us
->len
> NBITS
)
378 if (uf
->ptr
== NULL
) {
379 bit_nclear(ub
->map
, us
->len
, us
->len
+ uf
->len
- 1);
381 TAILQ_REMOVE(&uh
->head
, uf
, list
);
383 } else if (uf
->ptr
== uh
) {
384 bit_nset(ub
->map
, us
->len
, us
->len
+ uf
->len
- 1);
387 TAILQ_REMOVE(&uh
->head
, uf
, list
);
391 for (l
= 0; l
< uf
->len
; l
++, us
->len
++) {
392 if (bit_test(ubf
->map
, l
)) {
393 bit_set(ub
->map
, us
->len
);
396 bit_clear(ub
->map
, us
->len
);
399 TAILQ_REMOVE(&uh
->head
, uf
, list
);
407 * See if a given unr should be collapsed with a neighbor.
409 * NB: called from alloc_unr(), no new memory allocation allowed.
412 collapse_unr(struct unrhdr
*uh
, struct unr
*up
)
417 /* If bitmap is all set or clear, change it to runlength */
418 if (is_bitmap(uh
, up
)) {
420 if (ub
->busy
== up
->len
) {
421 delete_unr(uh
, up
->ptr
);
423 } else if (ub
->busy
== 0) {
424 delete_unr(uh
, up
->ptr
);
429 /* If nothing left in runlength, delete it */
431 upp
= TAILQ_PREV(up
, unrhd
, list
);
433 upp
= TAILQ_NEXT(up
, list
);
434 TAILQ_REMOVE(&uh
->head
, up
, list
);
439 /* If we have "hot-spot" still, merge with neighbor if possible */
441 upp
= TAILQ_PREV(up
, unrhd
, list
);
442 if (upp
!= NULL
&& up
->ptr
== upp
->ptr
) {
444 TAILQ_REMOVE(&uh
->head
, upp
, list
);
447 upp
= TAILQ_NEXT(up
, list
);
448 if (upp
!= NULL
&& up
->ptr
== upp
->ptr
) {
450 TAILQ_REMOVE(&uh
->head
, upp
, list
);
455 /* Merge into ->first if possible */
456 upp
= TAILQ_FIRST(&uh
->head
);
457 if (upp
!= NULL
&& upp
->ptr
== uh
) {
458 uh
->first
+= upp
->len
;
459 TAILQ_REMOVE(&uh
->head
, upp
, list
);
465 /* Merge into ->last if possible */
466 upp
= TAILQ_LAST(&uh
->head
, unrhd
);
467 if (upp
!= NULL
&& upp
->ptr
== NULL
) {
468 uh
->last
+= upp
->len
;
469 TAILQ_REMOVE(&uh
->head
, upp
, list
);
475 /* Try to make bitmaps */
476 while (optimize_unr(uh
))
481 * Allocate a free unr.
484 alloc_unrl(struct unrhdr
*uh
)
490 struct lock
*ml __debugvar
= uh
->lock
;
491 struct thread
*td __debugvar
= curthread
;
493 KKASSERT(lockstatus(ml
, td
) != 0);
494 check_unrhdr(uh
, __LINE__
);
495 x
= uh
->low
+ uh
->first
;
497 up
= TAILQ_FIRST(&uh
->head
);
500 * If we have an ideal split, just adjust the first+last
502 if (up
== NULL
&& uh
->last
> 0) {
510 * We can always allocate from the first list element, so if we have
511 * nothing on the list, we must have run out of unit numbers.
516 KASSERT(up
->ptr
!= uh
, ("UNR first element is allocated"));
518 if (up
->ptr
== NULL
) { /* free run */
521 } else { /* bitmap */
523 KASSERT(ub
->busy
< up
->len
, ("UNR bitmap confusion"));
524 bit_ffc(ub
->map
, up
->len
, &y
);
525 KASSERT(y
!= -1, ("UNR corruption: No clear bit in bitmap."));
531 collapse_unr(uh
, up
);
536 alloc_unr(struct unrhdr
*uh
)
540 lockmgr(uh
->lock
, LK_EXCLUSIVE
);
542 lockmgr(uh
->lock
, LK_RELEASE
);
549 * If we can save unrs by using a bitmap, do so.
552 free_unrl(struct unrhdr
*uh
, u_int item
, void **p1
, void **p2
)
554 struct unr
*up
, *upp
, *upn
;
558 KASSERT(item
>= uh
->low
&& item
<= uh
->high
,
559 ("UNR: free_unr(%u) out of range [%u...%u]",
560 item
, uh
->low
, uh
->high
));
561 check_unrhdr(uh
, __LINE__
);
563 upp
= TAILQ_FIRST(&uh
->head
);
565 * Freeing in the ideal split case
567 if (item
+ 1 == uh
->first
&& upp
== NULL
) {
571 check_unrhdr(uh
, __LINE__
);
575 * Freeing in the ->first section. Create a run starting at the
576 * freed item. The code below will subdivide it.
578 if (item
< uh
->first
) {
579 up
= new_unr(uh
, p1
, p2
);
581 up
->len
= uh
->first
- item
;
582 TAILQ_INSERT_HEAD(&uh
->head
, up
, list
);
583 uh
->first
-= up
->len
;
588 /* Find the item which contains the unit we want to free */
589 TAILQ_FOREACH(up
, &uh
->head
, list
) {
595 /* Handle bitmap items */
596 if (is_bitmap(uh
, up
)) {
599 KASSERT(bit_test(ub
->map
, item
) != 0,
600 ("UNR: Freeing free item %d (bitmap)\n", item
));
601 bit_clear(ub
->map
, item
);
604 collapse_unr(uh
, up
);
608 KASSERT(up
->ptr
== uh
, ("UNR Freeing free item %d (run))\n", item
));
610 /* Just this one left, reap it */
614 collapse_unr(uh
, up
);
618 /* Check if we can shift the item into the previous 'free' run */
619 upp
= TAILQ_PREV(up
, unrhd
, list
);
620 if (item
== 0 && upp
!= NULL
&& upp
->ptr
== NULL
) {
624 collapse_unr(uh
, up
);
628 /* Check if we can shift the item to the next 'free' run */
629 upn
= TAILQ_NEXT(up
, list
);
630 if (item
== up
->len
- 1 && upn
!= NULL
&& upn
->ptr
== NULL
) {
634 collapse_unr(uh
, up
);
638 /* Split off the tail end, if any. */
639 pl
= up
->len
- (1 + item
);
641 upp
= new_unr(uh
, p1
, p2
);
644 TAILQ_INSERT_AFTER(&uh
->head
, up
, upp
, list
);
647 /* Split off head end, if any */
649 upp
= new_unr(uh
, p1
, p2
);
652 TAILQ_INSERT_BEFORE(up
, upp
, list
);
657 collapse_unr(uh
, up
);
661 free_unr(struct unrhdr
*uh
, u_int item
)
665 p1
= Malloc(sizeof(struct unr
));
666 p2
= Malloc(sizeof(struct unr
));
667 lockmgr(uh
->lock
, LK_EXCLUSIVE
);
668 free_unrl(uh
, item
, &p1
, &p2
);
669 lockmgr(uh
->lock
, LK_RELEASE
);
676 #ifndef _KERNEL /* USERLAND test driver */
679 * Simple stochastic test driver for the above functions
683 print_unr(struct unrhdr
*uh
, struct unr
*up
)
688 printf(" %p len = %5u ", up
, up
->len
);
691 else if (up
->ptr
== uh
)
695 printf("bitmap(%d) [", ub
->busy
);
696 for (x
= 0; x
< up
->len
; x
++) {
697 if (bit_test(ub
->map
, x
))
707 print_unrhdr(struct unrhdr
*uh
)
713 "%p low = %u high = %u first = %u last = %u busy %u chunks = %u\n",
714 uh
, uh
->low
, uh
->high
, uh
->first
, uh
->last
, uh
->busy
, uh
->alloc
);
715 x
= uh
->low
+ uh
->first
;
716 TAILQ_FOREACH(up
, &uh
->head
, list
) {
717 printf(" from = %5u", x
);
719 if (up
->ptr
== NULL
|| up
->ptr
== uh
)
726 /* Number of unrs to test */
730 main(int argc __unused
, const char **argv __unused
)
736 setbuf(stdout
, NULL
);
737 uh
= new_unrhdr(0, NN
- 1, NULL
);
740 memset(a
, 0, sizeof a
);
742 fprintf(stderr
, "sizeof(struct unr) %d\n", sizeof (struct unr
));
743 fprintf(stderr
, "sizeof(struct unrb) %d\n", sizeof (struct unrb
));
744 fprintf(stderr
, "sizeof(struct unrhdr) %d\n", sizeof (struct unrhdr
));
745 fprintf(stderr
, "NBITS %d\n", NBITS
);
747 for (m
= 0; m
< NN
* 100; m
++) {
767 if (1) /* XXX: change this for detailed debug printout */
769 check_unrhdr(uh
, __LINE__
);
771 for (i
= 0; i
< NN
; i
++) {