Root/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)
86typedef s16 slobidx_t;
87#else
88typedef s32 slobidx_t;
89#endif
90
91struct slob_block {
92    slobidx_t units;
93};
94typedef 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
101static LIST_HEAD(free_slob_small);
102static LIST_HEAD(free_slob_medium);
103static LIST_HEAD(free_slob_large);
104
105/*
106 * slob_page_free: true for pages on free_slob_pages list.
107 */
108static inline int slob_page_free(struct page *sp)
109{
110    return PageSlobFree(sp);
111}
112
113static void set_slob_page_free(struct page *sp, struct list_head *list)
114{
115    list_add(&sp->list, list);
116    __SetPageSlobFree(sp);
117}
118
119static 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 */
134struct slob_rcu {
135    struct rcu_head head;
136    int size;
137};
138
139/*
140 * slob_lock protects all slob allocator structures.
141 */
142static DEFINE_SPINLOCK(slob_lock);
143
144/*
145 * Encode the given size and next info into a free slob block s.
146 */
147static 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 */
162static 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 */
172static 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 */
187static int slob_last(slob_t *s)
188{
189    return !((unsigned long)slob_next(s) & ~PAGE_MASK);
190}
191
192static void *slob_new_pages(gfp_t gfp, int order, int node)
193{
194    void *page;
195
196#ifdef CONFIG_NUMA
197    if (node != -1)
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
209static 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 */
219static 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 */
270static 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 != -1 && 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 */
342static 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    }
420out:
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
428void *__kmalloc_node(size_t size, gfp_t gfp, int node)
429{
430    unsigned int *m;
431    int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
432    void *ret;
433
434    gfp &= gfp_allowed_mask;
435
436    lockdep_trace_alloc(gfp);
437
438    if (size < PAGE_SIZE - align) {
439        if (!size)
440            return ZERO_SIZE_PTR;
441
442        m = slob_alloc(size + align, gfp, align, node);
443
444        if (!m)
445            return NULL;
446        *m = size;
447        ret = (void *)m + align;
448
449        trace_kmalloc_node(_RET_IP_, ret,
450                   size, size + align, gfp, node);
451    } else {
452        unsigned int order = get_order(size);
453
454        if (likely(order))
455            gfp |= __GFP_COMP;
456        ret = slob_new_pages(gfp, order, node);
457        if (ret) {
458            struct page *page;
459            page = virt_to_page(ret);
460            page->private = size;
461        }
462
463        trace_kmalloc_node(_RET_IP_, ret,
464                   size, PAGE_SIZE << order, gfp, node);
465    }
466
467    kmemleak_alloc(ret, size, 1, gfp);
468    return ret;
469}
470EXPORT_SYMBOL(__kmalloc_node);
471
472void kfree(const void *block)
473{
474    struct page *sp;
475
476    trace_kfree(_RET_IP_, block);
477
478    if (unlikely(ZERO_OR_NULL_PTR(block)))
479        return;
480    kmemleak_free(block);
481
482    sp = virt_to_page(block);
483    if (PageSlab(sp)) {
484        int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
485        unsigned int *m = (unsigned int *)(block - align);
486        slob_free(m, *m + align);
487    } else
488        put_page(sp);
489}
490EXPORT_SYMBOL(kfree);
491
492/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
493size_t ksize(const void *block)
494{
495    struct page *sp;
496
497    BUG_ON(!block);
498    if (unlikely(block == ZERO_SIZE_PTR))
499        return 0;
500
501    sp = virt_to_page(block);
502    if (PageSlab(sp)) {
503        int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
504        unsigned int *m = (unsigned int *)(block - align);
505        return SLOB_UNITS(*m) * SLOB_UNIT;
506    } else
507        return sp->private;
508}
509EXPORT_SYMBOL(ksize);
510
511struct kmem_cache *__kmem_cache_create(const char *name, size_t size,
512    size_t align, unsigned long flags, void (*ctor)(void *))
513{
514    struct kmem_cache *c;
515
516    c = slob_alloc(sizeof(struct kmem_cache),
517        GFP_KERNEL, ARCH_KMALLOC_MINALIGN, -1);
518
519    if (c) {
520        c->name = name;
521        c->size = size;
522        if (flags & SLAB_DESTROY_BY_RCU) {
523            /* leave room for rcu footer at the end of object */
524            c->size += sizeof(struct slob_rcu);
525        }
526        c->flags = flags;
527        c->ctor = ctor;
528        /* ignore alignment unless it's forced */
529        c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
530        if (c->align < ARCH_SLAB_MINALIGN)
531            c->align = ARCH_SLAB_MINALIGN;
532        if (c->align < align)
533            c->align = align;
534
535        kmemleak_alloc(c, sizeof(struct kmem_cache), 1, GFP_KERNEL);
536        c->refcount = 1;
537    }
538    return c;
539}
540
541void kmem_cache_destroy(struct kmem_cache *c)
542{
543    kmemleak_free(c);
544    if (c->flags & SLAB_DESTROY_BY_RCU)
545        rcu_barrier();
546    slob_free(c, sizeof(struct kmem_cache));
547}
548EXPORT_SYMBOL(kmem_cache_destroy);
549
550void *kmem_cache_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
551{
552    void *b;
553
554    flags &= gfp_allowed_mask;
555
556    lockdep_trace_alloc(flags);
557
558    if (c->size < PAGE_SIZE) {
559        b = slob_alloc(c->size, flags, c->align, node);
560        trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
561                        SLOB_UNITS(c->size) * SLOB_UNIT,
562                        flags, node);
563    } else {
564        b = slob_new_pages(flags, get_order(c->size), node);
565        trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
566                        PAGE_SIZE << get_order(c->size),
567                        flags, node);
568    }
569
570    if (c->ctor)
571        c->ctor(b);
572
573    kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
574    return b;
575}
576EXPORT_SYMBOL(kmem_cache_alloc_node);
577
578static void __kmem_cache_free(void *b, int size)
579{
580    if (size < PAGE_SIZE)
581        slob_free(b, size);
582    else
583        slob_free_pages(b, get_order(size));
584}
585
586static void kmem_rcu_free(struct rcu_head *head)
587{
588    struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
589    void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
590
591    __kmem_cache_free(b, slob_rcu->size);
592}
593
594void kmem_cache_free(struct kmem_cache *c, void *b)
595{
596    kmemleak_free_recursive(b, c->flags);
597    if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) {
598        struct slob_rcu *slob_rcu;
599        slob_rcu = b + (c->size - sizeof(struct slob_rcu));
600        slob_rcu->size = c->size;
601        call_rcu(&slob_rcu->head, kmem_rcu_free);
602    } else {
603        __kmem_cache_free(b, c->size);
604    }
605
606    trace_kmem_cache_free(_RET_IP_, b);
607}
608EXPORT_SYMBOL(kmem_cache_free);
609
610unsigned int kmem_cache_size(struct kmem_cache *c)
611{
612    return c->size;
613}
614EXPORT_SYMBOL(kmem_cache_size);
615
616int kmem_cache_shrink(struct kmem_cache *d)
617{
618    return 0;
619}
620EXPORT_SYMBOL(kmem_cache_shrink);
621
622void __init kmem_cache_init(void)
623{
624    slab_state = UP;
625}
626
627void __init kmem_cache_init_late(void)
628{
629    slab_state = FULL;
630}
631

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jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9



interactive