]>
git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - mm/slob.c
2 * SLOB Allocator: Simple List Of Blocks
4 * Matt Mackall <mpm@selenic.com> 12/30/03
6 * NUMA support by Paul Mundt, 2007.
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.
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.
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.
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()
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
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().
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.
60 #include <linux/kernel.h>
61 #include <linux/slab.h>
63 #include <linux/swap.h> /* struct reclaim_state */
64 #include <linux/cache.h>
65 #include <linux/init.h>
66 #include <linux/module.h>
67 #include <linux/rcupdate.h>
68 #include <linux/list.h>
69 #include <linux/kmemtrace.h>
70 #include <linux/kmemleak.h>
71 #include <asm/atomic.h>
74 * slob_block has a field 'units', which indicates size of block if +ve,
75 * or offset of next block if -ve (in SLOB_UNITs).
77 * Free blocks of size 1 unit simply contain the offset of the next block.
78 * Those with larger size contain their size in the first SLOB_UNIT of
79 * memory, and the offset of the next free block in the second SLOB_UNIT.
81 #if PAGE_SIZE <= (32767 * 2)
82 typedef s16 slobidx_t
;
84 typedef s32 slobidx_t
;
90 typedef struct slob_block slob_t
;
93 * We use struct page fields to manage some slob allocation aspects,
94 * however to avoid the horrible mess in include/linux/mm_types.h, we'll
95 * just define our own struct page type variant here.
100 unsigned long flags
; /* mandatory */
101 atomic_t _count
; /* mandatory */
102 slobidx_t units
; /* free units left in page */
103 unsigned long pad
[2];
104 slob_t
*free
; /* first free slob_t in page */
105 struct list_head list
; /* linked list of free pages */
110 static inline void struct_slob_page_wrong_size(void)
111 { BUILD_BUG_ON(sizeof(struct slob_page
) != sizeof(struct page
)); }
114 * free_slob_page: call before a slob_page is returned to the page allocator.
116 static inline void free_slob_page(struct slob_page
*sp
)
118 reset_page_mapcount(&sp
->page
);
119 sp
->page
.mapping
= NULL
;
123 * All partially free slob pages go on these lists.
125 #define SLOB_BREAK1 256
126 #define SLOB_BREAK2 1024
127 static LIST_HEAD(free_slob_small
);
128 static LIST_HEAD(free_slob_medium
);
129 static LIST_HEAD(free_slob_large
);
132 * is_slob_page: True for all slob pages (false for bigblock pages)
134 static inline int is_slob_page(struct slob_page
*sp
)
136 return PageSlab((struct page
*)sp
);
139 static inline void set_slob_page(struct slob_page
*sp
)
141 __SetPageSlab((struct page
*)sp
);
144 static inline void clear_slob_page(struct slob_page
*sp
)
146 __ClearPageSlab((struct page
*)sp
);
149 static inline struct slob_page
*slob_page(const void *addr
)
151 return (struct slob_page
*)virt_to_page(addr
);
155 * slob_page_free: true for pages on free_slob_pages list.
157 static inline int slob_page_free(struct slob_page
*sp
)
159 return PageSlobFree((struct page
*)sp
);
162 static void set_slob_page_free(struct slob_page
*sp
, struct list_head
*list
)
164 list_add(&sp
->list
, list
);
165 __SetPageSlobFree((struct page
*)sp
);
168 static inline void clear_slob_page_free(struct slob_page
*sp
)
171 __ClearPageSlobFree((struct page
*)sp
);
174 #define SLOB_UNIT sizeof(slob_t)
175 #define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
176 #define SLOB_ALIGN L1_CACHE_BYTES
179 * struct slob_rcu is inserted at the tail of allocated slob blocks, which
180 * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
181 * the block using call_rcu.
184 struct rcu_head head
;
189 * slob_lock protects all slob allocator structures.
191 static DEFINE_SPINLOCK(slob_lock
);
194 * Encode the given size and next info into a free slob block s.
196 static void set_slob(slob_t
*s
, slobidx_t size
, slob_t
*next
)
198 slob_t
*base
= (slob_t
*)((unsigned long)s
& PAGE_MASK
);
199 slobidx_t offset
= next
- base
;
205 s
[0].units
= -offset
;
209 * Return the size of a slob block.
211 static slobidx_t
slob_units(slob_t
*s
)
219 * Return the next free slob block pointer after this one.
221 static slob_t
*slob_next(slob_t
*s
)
223 slob_t
*base
= (slob_t
*)((unsigned long)s
& PAGE_MASK
);
234 * Returns true if s is the last free block in its page.
236 static int slob_last(slob_t
*s
)
238 return !((unsigned long)slob_next(s
) & ~PAGE_MASK
);
241 static void *slob_new_pages(gfp_t gfp
, int order
, int node
)
247 page
= alloc_pages_exact_node(node
, gfp
, order
);
250 page
= alloc_pages(gfp
, order
);
255 return page_address(page
);
258 static void slob_free_pages(void *b
, int order
)
260 if (current
->reclaim_state
)
261 current
->reclaim_state
->reclaimed_slab
+= 1 << order
;
262 free_pages((unsigned long)b
, order
);
266 * Allocate a slob block within a given slob_page sp.
268 static void *slob_page_alloc(struct slob_page
*sp
, size_t size
, int align
)
270 slob_t
*prev
, *cur
, *aligned
= NULL
;
271 int delta
= 0, units
= SLOB_UNITS(size
);
273 for (prev
= NULL
, cur
= sp
->free
; ; prev
= cur
, cur
= slob_next(cur
)) {
274 slobidx_t avail
= slob_units(cur
);
277 aligned
= (slob_t
*)ALIGN((unsigned long)cur
, align
);
278 delta
= aligned
- cur
;
280 if (avail
>= units
+ delta
) { /* room enough? */
283 if (delta
) { /* need to fragment head to align? */
284 next
= slob_next(cur
);
285 set_slob(aligned
, avail
- delta
, next
);
286 set_slob(cur
, delta
, aligned
);
289 avail
= slob_units(cur
);
292 next
= slob_next(cur
);
293 if (avail
== units
) { /* exact fit? unlink. */
295 set_slob(prev
, slob_units(prev
), next
);
298 } else { /* fragment */
300 set_slob(prev
, slob_units(prev
), cur
+ units
);
302 sp
->free
= cur
+ units
;
303 set_slob(cur
+ units
, avail
- units
, next
);
308 clear_slob_page_free(sp
);
317 * slob_alloc: entry point into the slob allocator.
319 static void *slob_alloc(size_t size
, gfp_t gfp
, int align
, int node
)
321 struct slob_page
*sp
;
322 struct list_head
*prev
;
323 struct list_head
*slob_list
;
327 if (size
< SLOB_BREAK1
)
328 slob_list
= &free_slob_small
;
329 else if (size
< SLOB_BREAK2
)
330 slob_list
= &free_slob_medium
;
332 slob_list
= &free_slob_large
;
334 spin_lock_irqsave(&slob_lock
, flags
);
335 /* Iterate through each partially free page, try to find room */
336 list_for_each_entry(sp
, slob_list
, list
) {
339 * If there's a node specification, search for a partial
340 * page with a matching node id in the freelist.
342 if (node
!= -1 && page_to_nid(&sp
->page
) != node
)
345 /* Enough room on this page? */
346 if (sp
->units
< SLOB_UNITS(size
))
349 /* Attempt to alloc */
350 prev
= sp
->list
.prev
;
351 b
= slob_page_alloc(sp
, size
, align
);
355 /* Improve fragment distribution and reduce our average
356 * search time by starting our next search here. (see
357 * Knuth vol 1, sec 2.5, pg 449) */
358 if (prev
!= slob_list
->prev
&&
359 slob_list
->next
!= prev
->next
)
360 list_move_tail(slob_list
, prev
->next
);
363 spin_unlock_irqrestore(&slob_lock
, flags
);
365 /* Not enough space: must allocate a new page */
367 b
= slob_new_pages(gfp
& ~__GFP_ZERO
, 0, node
);
373 spin_lock_irqsave(&slob_lock
, flags
);
374 sp
->units
= SLOB_UNITS(PAGE_SIZE
);
376 INIT_LIST_HEAD(&sp
->list
);
377 set_slob(b
, SLOB_UNITS(PAGE_SIZE
), b
+ SLOB_UNITS(PAGE_SIZE
));
378 set_slob_page_free(sp
, slob_list
);
379 b
= slob_page_alloc(sp
, size
, align
);
381 spin_unlock_irqrestore(&slob_lock
, flags
);
383 if (unlikely((gfp
& __GFP_ZERO
) && b
))
389 * slob_free: entry point into the slob allocator.
391 static void slob_free(void *block
, int size
)
393 struct slob_page
*sp
;
394 slob_t
*prev
, *next
, *b
= (slob_t
*)block
;
398 if (unlikely(ZERO_OR_NULL_PTR(block
)))
402 sp
= slob_page(block
);
403 units
= SLOB_UNITS(size
);
405 spin_lock_irqsave(&slob_lock
, flags
);
407 if (sp
->units
+ units
== SLOB_UNITS(PAGE_SIZE
)) {
408 /* Go directly to page allocator. Do not pass slob allocator */
409 if (slob_page_free(sp
))
410 clear_slob_page_free(sp
);
411 spin_unlock_irqrestore(&slob_lock
, flags
);
414 slob_free_pages(b
, 0);
418 if (!slob_page_free(sp
)) {
419 /* This slob page is about to become partially free. Easy! */
423 (void *)((unsigned long)(b
+
424 SLOB_UNITS(PAGE_SIZE
)) & PAGE_MASK
));
425 set_slob_page_free(sp
, &free_slob_small
);
430 * Otherwise the page is already partially free, so find reinsertion
436 if (b
+ units
== sp
->free
) {
437 units
+= slob_units(sp
->free
);
438 sp
->free
= slob_next(sp
->free
);
440 set_slob(b
, units
, sp
->free
);
444 next
= slob_next(prev
);
447 next
= slob_next(prev
);
450 if (!slob_last(prev
) && b
+ units
== next
) {
451 units
+= slob_units(next
);
452 set_slob(b
, units
, slob_next(next
));
454 set_slob(b
, units
, next
);
456 if (prev
+ slob_units(prev
) == b
) {
457 units
= slob_units(b
) + slob_units(prev
);
458 set_slob(prev
, units
, slob_next(b
));
460 set_slob(prev
, slob_units(prev
), b
);
463 spin_unlock_irqrestore(&slob_lock
, flags
);
467 * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
470 #ifndef ARCH_KMALLOC_MINALIGN
471 #define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long)
474 #ifndef ARCH_SLAB_MINALIGN
475 #define ARCH_SLAB_MINALIGN __alignof__(unsigned long)
478 void *__kmalloc_node(size_t size
, gfp_t gfp
, int node
)
481 int align
= max(ARCH_KMALLOC_MINALIGN
, ARCH_SLAB_MINALIGN
);
484 lockdep_trace_alloc(gfp
);
486 if (size
< PAGE_SIZE
- align
) {
488 return ZERO_SIZE_PTR
;
490 m
= slob_alloc(size
+ align
, gfp
, align
, node
);
495 ret
= (void *)m
+ align
;
497 trace_kmalloc_node(_RET_IP_
, ret
,
498 size
, size
+ align
, gfp
, node
);
500 unsigned int order
= get_order(size
);
502 ret
= slob_new_pages(gfp
| __GFP_COMP
, get_order(size
), node
);
505 page
= virt_to_page(ret
);
506 page
->private = size
;
509 trace_kmalloc_node(_RET_IP_
, ret
,
510 size
, PAGE_SIZE
<< order
, gfp
, node
);
513 kmemleak_alloc(ret
, size
, 1, gfp
);
516 EXPORT_SYMBOL(__kmalloc_node
);
518 void kfree(const void *block
)
520 struct slob_page
*sp
;
522 trace_kfree(_RET_IP_
, block
);
524 if (unlikely(ZERO_OR_NULL_PTR(block
)))
526 kmemleak_free(block
);
528 sp
= slob_page(block
);
529 if (is_slob_page(sp
)) {
530 int align
= max(ARCH_KMALLOC_MINALIGN
, ARCH_SLAB_MINALIGN
);
531 unsigned int *m
= (unsigned int *)(block
- align
);
532 slob_free(m
, *m
+ align
);
536 EXPORT_SYMBOL(kfree
);
538 /* can't use ksize for kmem_cache_alloc memory, only kmalloc */
539 size_t ksize(const void *block
)
541 struct slob_page
*sp
;
544 if (unlikely(block
== ZERO_SIZE_PTR
))
547 sp
= slob_page(block
);
548 if (is_slob_page(sp
)) {
549 int align
= max(ARCH_KMALLOC_MINALIGN
, ARCH_SLAB_MINALIGN
);
550 unsigned int *m
= (unsigned int *)(block
- align
);
551 return SLOB_UNITS(*m
) * SLOB_UNIT
;
553 return sp
->page
.private;
555 EXPORT_SYMBOL(ksize
);
558 unsigned int size
, align
;
561 void (*ctor
)(void *);
564 struct kmem_cache
*kmem_cache_create(const char *name
, size_t size
,
565 size_t align
, unsigned long flags
, void (*ctor
)(void *))
567 struct kmem_cache
*c
;
569 c
= slob_alloc(sizeof(struct kmem_cache
),
570 GFP_KERNEL
, ARCH_KMALLOC_MINALIGN
, -1);
575 if (flags
& SLAB_DESTROY_BY_RCU
) {
576 /* leave room for rcu footer at the end of object */
577 c
->size
+= sizeof(struct slob_rcu
);
581 /* ignore alignment unless it's forced */
582 c
->align
= (flags
& SLAB_HWCACHE_ALIGN
) ? SLOB_ALIGN
: 0;
583 if (c
->align
< ARCH_SLAB_MINALIGN
)
584 c
->align
= ARCH_SLAB_MINALIGN
;
585 if (c
->align
< align
)
587 } else if (flags
& SLAB_PANIC
)
588 panic("Cannot create slab cache %s\n", name
);
590 kmemleak_alloc(c
, sizeof(struct kmem_cache
), 1, GFP_KERNEL
);
593 EXPORT_SYMBOL(kmem_cache_create
);
595 void kmem_cache_destroy(struct kmem_cache
*c
)
598 if (c
->flags
& SLAB_DESTROY_BY_RCU
)
600 slob_free(c
, sizeof(struct kmem_cache
));
602 EXPORT_SYMBOL(kmem_cache_destroy
);
604 void *kmem_cache_alloc_node(struct kmem_cache
*c
, gfp_t flags
, int node
)
608 if (c
->size
< PAGE_SIZE
) {
609 b
= slob_alloc(c
->size
, flags
, c
->align
, node
);
610 trace_kmem_cache_alloc_node(_RET_IP_
, b
, c
->size
,
611 SLOB_UNITS(c
->size
) * SLOB_UNIT
,
614 b
= slob_new_pages(flags
, get_order(c
->size
), node
);
615 trace_kmem_cache_alloc_node(_RET_IP_
, b
, c
->size
,
616 PAGE_SIZE
<< get_order(c
->size
),
623 kmemleak_alloc_recursive(b
, c
->size
, 1, c
->flags
, flags
);
626 EXPORT_SYMBOL(kmem_cache_alloc_node
);
628 static void __kmem_cache_free(void *b
, int size
)
630 if (size
< PAGE_SIZE
)
633 slob_free_pages(b
, get_order(size
));
636 static void kmem_rcu_free(struct rcu_head
*head
)
638 struct slob_rcu
*slob_rcu
= (struct slob_rcu
*)head
;
639 void *b
= (void *)slob_rcu
- (slob_rcu
->size
- sizeof(struct slob_rcu
));
641 __kmem_cache_free(b
, slob_rcu
->size
);
644 void kmem_cache_free(struct kmem_cache
*c
, void *b
)
646 kmemleak_free_recursive(b
, c
->flags
);
647 if (unlikely(c
->flags
& SLAB_DESTROY_BY_RCU
)) {
648 struct slob_rcu
*slob_rcu
;
649 slob_rcu
= b
+ (c
->size
- sizeof(struct slob_rcu
));
650 INIT_RCU_HEAD(&slob_rcu
->head
);
651 slob_rcu
->size
= c
->size
;
652 call_rcu(&slob_rcu
->head
, kmem_rcu_free
);
654 __kmem_cache_free(b
, c
->size
);
657 trace_kmem_cache_free(_RET_IP_
, b
);
659 EXPORT_SYMBOL(kmem_cache_free
);
661 unsigned int kmem_cache_size(struct kmem_cache
*c
)
665 EXPORT_SYMBOL(kmem_cache_size
);
667 const char *kmem_cache_name(struct kmem_cache
*c
)
671 EXPORT_SYMBOL(kmem_cache_name
);
673 int kmem_cache_shrink(struct kmem_cache
*d
)
677 EXPORT_SYMBOL(kmem_cache_shrink
);
679 int kmem_ptr_validate(struct kmem_cache
*a
, const void *b
)
684 static unsigned int slob_ready __read_mostly
;
686 int slab_is_available(void)
691 void __init
kmem_cache_init(void)
696 void __init
kmem_cache_init_late(void)