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git.proxmox.com Git - mirror_ubuntu-bionic-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_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/cache.h>
64 #include <linux/init.h>
65 #include <linux/module.h>
66 #include <linux/rcupdate.h>
67 #include <linux/list.h>
68 #include <asm/atomic.h>
71 * slob_block has a field 'units', which indicates size of block if +ve,
72 * or offset of next block if -ve (in SLOB_UNITs).
74 * Free blocks of size 1 unit simply contain the offset of the next block.
75 * Those with larger size contain their size in the first SLOB_UNIT of
76 * memory, and the offset of the next free block in the second SLOB_UNIT.
78 #if PAGE_SIZE <= (32767 * 2)
79 typedef s16 slobidx_t
;
81 typedef s32 slobidx_t
;
87 typedef struct slob_block slob_t
;
90 * We use struct page fields to manage some slob allocation aspects,
91 * however to avoid the horrible mess in include/linux/mm_types.h, we'll
92 * just define our own struct page type variant here.
97 unsigned long flags
; /* mandatory */
98 atomic_t _count
; /* mandatory */
99 slobidx_t units
; /* free units left in page */
100 unsigned long pad
[2];
101 slob_t
*free
; /* first free slob_t in page */
102 struct list_head list
; /* linked list of free pages */
107 static inline void struct_slob_page_wrong_size(void)
108 { BUILD_BUG_ON(sizeof(struct slob_page
) != sizeof(struct page
)); }
111 * free_slob_page: call before a slob_page is returned to the page allocator.
113 static inline void free_slob_page(struct slob_page
*sp
)
115 reset_page_mapcount(&sp
->page
);
116 sp
->page
.mapping
= NULL
;
120 * All partially free slob pages go on these lists.
122 #define SLOB_BREAK1 256
123 #define SLOB_BREAK2 1024
124 static LIST_HEAD(free_slob_small
);
125 static LIST_HEAD(free_slob_medium
);
126 static LIST_HEAD(free_slob_large
);
129 * is_slob_page: True for all slob pages (false for bigblock pages)
131 static inline int is_slob_page(struct slob_page
*sp
)
133 return PageSlobPage((struct page
*)sp
);
136 static inline void set_slob_page(struct slob_page
*sp
)
138 __SetPageSlobPage((struct page
*)sp
);
141 static inline void clear_slob_page(struct slob_page
*sp
)
143 __ClearPageSlobPage((struct page
*)sp
);
146 static inline struct slob_page
*slob_page(const void *addr
)
148 return (struct slob_page
*)virt_to_page(addr
);
152 * slob_page_free: true for pages on free_slob_pages list.
154 static inline int slob_page_free(struct slob_page
*sp
)
156 return PageSlobFree((struct page
*)sp
);
159 static void set_slob_page_free(struct slob_page
*sp
, struct list_head
*list
)
161 list_add(&sp
->list
, list
);
162 __SetPageSlobFree((struct page
*)sp
);
165 static inline void clear_slob_page_free(struct slob_page
*sp
)
168 __ClearPageSlobFree((struct page
*)sp
);
171 #define SLOB_UNIT sizeof(slob_t)
172 #define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
173 #define SLOB_ALIGN L1_CACHE_BYTES
176 * struct slob_rcu is inserted at the tail of allocated slob blocks, which
177 * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
178 * the block using call_rcu.
181 struct rcu_head head
;
186 * slob_lock protects all slob allocator structures.
188 static DEFINE_SPINLOCK(slob_lock
);
191 * Encode the given size and next info into a free slob block s.
193 static void set_slob(slob_t
*s
, slobidx_t size
, slob_t
*next
)
195 slob_t
*base
= (slob_t
*)((unsigned long)s
& PAGE_MASK
);
196 slobidx_t offset
= next
- base
;
202 s
[0].units
= -offset
;
206 * Return the size of a slob block.
208 static slobidx_t
slob_units(slob_t
*s
)
216 * Return the next free slob block pointer after this one.
218 static slob_t
*slob_next(slob_t
*s
)
220 slob_t
*base
= (slob_t
*)((unsigned long)s
& PAGE_MASK
);
231 * Returns true if s is the last free block in its page.
233 static int slob_last(slob_t
*s
)
235 return !((unsigned long)slob_next(s
) & ~PAGE_MASK
);
238 static void *slob_new_pages(gfp_t gfp
, int order
, int node
)
244 page
= alloc_pages_node(node
, gfp
, order
);
247 page
= alloc_pages(gfp
, order
);
252 return page_address(page
);
255 static void slob_free_pages(void *b
, int order
)
257 free_pages((unsigned long)b
, order
);
261 * Allocate a slob block within a given slob_page sp.
263 static void *slob_page_alloc(struct slob_page
*sp
, size_t size
, int align
)
265 slob_t
*prev
, *cur
, *aligned
= NULL
;
266 int delta
= 0, units
= SLOB_UNITS(size
);
268 for (prev
= NULL
, cur
= sp
->free
; ; prev
= cur
, cur
= slob_next(cur
)) {
269 slobidx_t avail
= slob_units(cur
);
272 aligned
= (slob_t
*)ALIGN((unsigned long)cur
, align
);
273 delta
= aligned
- cur
;
275 if (avail
>= units
+ delta
) { /* room enough? */
278 if (delta
) { /* need to fragment head to align? */
279 next
= slob_next(cur
);
280 set_slob(aligned
, avail
- delta
, next
);
281 set_slob(cur
, delta
, aligned
);
284 avail
= slob_units(cur
);
287 next
= slob_next(cur
);
288 if (avail
== units
) { /* exact fit? unlink. */
290 set_slob(prev
, slob_units(prev
), next
);
293 } else { /* fragment */
295 set_slob(prev
, slob_units(prev
), cur
+ units
);
297 sp
->free
= cur
+ units
;
298 set_slob(cur
+ units
, avail
- units
, next
);
303 clear_slob_page_free(sp
);
312 * slob_alloc: entry point into the slob allocator.
314 static void *slob_alloc(size_t size
, gfp_t gfp
, int align
, int node
)
316 struct slob_page
*sp
;
317 struct list_head
*prev
;
318 struct list_head
*slob_list
;
322 if (size
< SLOB_BREAK1
)
323 slob_list
= &free_slob_small
;
324 else if (size
< SLOB_BREAK2
)
325 slob_list
= &free_slob_medium
;
327 slob_list
= &free_slob_large
;
329 spin_lock_irqsave(&slob_lock
, flags
);
330 /* Iterate through each partially free page, try to find room */
331 list_for_each_entry(sp
, slob_list
, list
) {
334 * If there's a node specification, search for a partial
335 * page with a matching node id in the freelist.
337 if (node
!= -1 && page_to_nid(&sp
->page
) != node
)
340 /* Enough room on this page? */
341 if (sp
->units
< SLOB_UNITS(size
))
344 /* Attempt to alloc */
345 prev
= sp
->list
.prev
;
346 b
= slob_page_alloc(sp
, size
, align
);
350 /* Improve fragment distribution and reduce our average
351 * search time by starting our next search here. (see
352 * Knuth vol 1, sec 2.5, pg 449) */
353 if (prev
!= slob_list
->prev
&&
354 slob_list
->next
!= prev
->next
)
355 list_move_tail(slob_list
, prev
->next
);
358 spin_unlock_irqrestore(&slob_lock
, flags
);
360 /* Not enough space: must allocate a new page */
362 b
= slob_new_pages(gfp
& ~__GFP_ZERO
, 0, node
);
368 spin_lock_irqsave(&slob_lock
, flags
);
369 sp
->units
= SLOB_UNITS(PAGE_SIZE
);
371 INIT_LIST_HEAD(&sp
->list
);
372 set_slob(b
, SLOB_UNITS(PAGE_SIZE
), b
+ SLOB_UNITS(PAGE_SIZE
));
373 set_slob_page_free(sp
, slob_list
);
374 b
= slob_page_alloc(sp
, size
, align
);
376 spin_unlock_irqrestore(&slob_lock
, flags
);
378 if (unlikely((gfp
& __GFP_ZERO
) && b
))
384 * slob_free: entry point into the slob allocator.
386 static void slob_free(void *block
, int size
)
388 struct slob_page
*sp
;
389 slob_t
*prev
, *next
, *b
= (slob_t
*)block
;
393 if (unlikely(ZERO_OR_NULL_PTR(block
)))
397 sp
= slob_page(block
);
398 units
= SLOB_UNITS(size
);
400 spin_lock_irqsave(&slob_lock
, flags
);
402 if (sp
->units
+ units
== SLOB_UNITS(PAGE_SIZE
)) {
403 /* Go directly to page allocator. Do not pass slob allocator */
404 if (slob_page_free(sp
))
405 clear_slob_page_free(sp
);
406 spin_unlock_irqrestore(&slob_lock
, flags
);
409 free_page((unsigned long)b
);
413 if (!slob_page_free(sp
)) {
414 /* This slob page is about to become partially free. Easy! */
418 (void *)((unsigned long)(b
+
419 SLOB_UNITS(PAGE_SIZE
)) & PAGE_MASK
));
420 set_slob_page_free(sp
, &free_slob_small
);
425 * Otherwise the page is already partially free, so find reinsertion
431 if (b
+ units
== sp
->free
) {
432 units
+= slob_units(sp
->free
);
433 sp
->free
= slob_next(sp
->free
);
435 set_slob(b
, units
, sp
->free
);
439 next
= slob_next(prev
);
442 next
= slob_next(prev
);
445 if (!slob_last(prev
) && b
+ units
== next
) {
446 units
+= slob_units(next
);
447 set_slob(b
, units
, slob_next(next
));
449 set_slob(b
, units
, next
);
451 if (prev
+ slob_units(prev
) == b
) {
452 units
= slob_units(b
) + slob_units(prev
);
453 set_slob(prev
, units
, slob_next(b
));
455 set_slob(prev
, slob_units(prev
), b
);
458 spin_unlock_irqrestore(&slob_lock
, flags
);
462 * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
465 #ifndef ARCH_KMALLOC_MINALIGN
466 #define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long)
469 #ifndef ARCH_SLAB_MINALIGN
470 #define ARCH_SLAB_MINALIGN __alignof__(unsigned long)
473 void *__kmalloc_node(size_t size
, gfp_t gfp
, int node
)
476 int align
= max(ARCH_KMALLOC_MINALIGN
, ARCH_SLAB_MINALIGN
);
478 lockdep_trace_alloc(gfp
);
480 if (size
< PAGE_SIZE
- align
) {
482 return ZERO_SIZE_PTR
;
484 m
= slob_alloc(size
+ align
, gfp
, align
, node
);
488 return (void *)m
+ align
;
492 ret
= slob_new_pages(gfp
| __GFP_COMP
, get_order(size
), node
);
495 page
= virt_to_page(ret
);
496 page
->private = size
;
501 EXPORT_SYMBOL(__kmalloc_node
);
503 void kfree(const void *block
)
505 struct slob_page
*sp
;
507 if (unlikely(ZERO_OR_NULL_PTR(block
)))
510 sp
= slob_page(block
);
511 if (is_slob_page(sp
)) {
512 int align
= max(ARCH_KMALLOC_MINALIGN
, ARCH_SLAB_MINALIGN
);
513 unsigned int *m
= (unsigned int *)(block
- align
);
514 slob_free(m
, *m
+ align
);
518 EXPORT_SYMBOL(kfree
);
520 /* can't use ksize for kmem_cache_alloc memory, only kmalloc */
521 size_t ksize(const void *block
)
523 struct slob_page
*sp
;
526 if (unlikely(block
== ZERO_SIZE_PTR
))
529 sp
= slob_page(block
);
530 if (is_slob_page(sp
)) {
531 int align
= max(ARCH_KMALLOC_MINALIGN
, ARCH_SLAB_MINALIGN
);
532 unsigned int *m
= (unsigned int *)(block
- align
);
533 return SLOB_UNITS(*m
) * SLOB_UNIT
;
535 return sp
->page
.private;
537 EXPORT_SYMBOL(ksize
);
540 unsigned int size
, align
;
543 void (*ctor
)(void *);
546 struct kmem_cache
*kmem_cache_create(const char *name
, size_t size
,
547 size_t align
, unsigned long flags
, void (*ctor
)(void *))
549 struct kmem_cache
*c
;
551 c
= slob_alloc(sizeof(struct kmem_cache
),
552 GFP_KERNEL
, ARCH_KMALLOC_MINALIGN
, -1);
557 if (flags
& SLAB_DESTROY_BY_RCU
) {
558 /* leave room for rcu footer at the end of object */
559 c
->size
+= sizeof(struct slob_rcu
);
563 /* ignore alignment unless it's forced */
564 c
->align
= (flags
& SLAB_HWCACHE_ALIGN
) ? SLOB_ALIGN
: 0;
565 if (c
->align
< ARCH_SLAB_MINALIGN
)
566 c
->align
= ARCH_SLAB_MINALIGN
;
567 if (c
->align
< align
)
569 } else if (flags
& SLAB_PANIC
)
570 panic("Cannot create slab cache %s\n", name
);
574 EXPORT_SYMBOL(kmem_cache_create
);
576 void kmem_cache_destroy(struct kmem_cache
*c
)
578 slob_free(c
, sizeof(struct kmem_cache
));
580 EXPORT_SYMBOL(kmem_cache_destroy
);
582 void *kmem_cache_alloc_node(struct kmem_cache
*c
, gfp_t flags
, int node
)
586 if (c
->size
< PAGE_SIZE
)
587 b
= slob_alloc(c
->size
, flags
, c
->align
, node
);
589 b
= slob_new_pages(flags
, get_order(c
->size
), node
);
596 EXPORT_SYMBOL(kmem_cache_alloc_node
);
598 static void __kmem_cache_free(void *b
, int size
)
600 if (size
< PAGE_SIZE
)
603 slob_free_pages(b
, get_order(size
));
606 static void kmem_rcu_free(struct rcu_head
*head
)
608 struct slob_rcu
*slob_rcu
= (struct slob_rcu
*)head
;
609 void *b
= (void *)slob_rcu
- (slob_rcu
->size
- sizeof(struct slob_rcu
));
611 __kmem_cache_free(b
, slob_rcu
->size
);
614 void kmem_cache_free(struct kmem_cache
*c
, void *b
)
616 if (unlikely(c
->flags
& SLAB_DESTROY_BY_RCU
)) {
617 struct slob_rcu
*slob_rcu
;
618 slob_rcu
= b
+ (c
->size
- sizeof(struct slob_rcu
));
619 INIT_RCU_HEAD(&slob_rcu
->head
);
620 slob_rcu
->size
= c
->size
;
621 call_rcu(&slob_rcu
->head
, kmem_rcu_free
);
623 __kmem_cache_free(b
, c
->size
);
626 EXPORT_SYMBOL(kmem_cache_free
);
628 unsigned int kmem_cache_size(struct kmem_cache
*c
)
632 EXPORT_SYMBOL(kmem_cache_size
);
634 const char *kmem_cache_name(struct kmem_cache
*c
)
638 EXPORT_SYMBOL(kmem_cache_name
);
640 int kmem_cache_shrink(struct kmem_cache
*d
)
644 EXPORT_SYMBOL(kmem_cache_shrink
);
646 int kmem_ptr_validate(struct kmem_cache
*a
, const void *b
)
651 static unsigned int slob_ready __read_mostly
;
653 int slab_is_available(void)
658 void __init
kmem_cache_init(void)