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Matt Mackall10cef602006-01-08 01:01:45 -08001/*
2 * SLOB Allocator: Simple List Of Blocks
3 *
4 * Matt Mackall <mpm@selenic.com> 12/30/03
5 *
6 * How SLOB works:
7 *
8 * The core of SLOB is a traditional K&R style heap allocator, with
9 * support for returning aligned objects. The granularity of this
10 * allocator is 8 bytes on x86, though it's perhaps possible to reduce
11 * this to 4 if it's deemed worth the effort. The slob heap is a
12 * singly-linked list of pages from __get_free_page, grown on demand
13 * and allocation from the heap is currently first-fit.
14 *
15 * Above this is an implementation of kmalloc/kfree. Blocks returned
16 * from kmalloc are 8-byte aligned and prepended with a 8-byte header.
17 * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
18 * __get_free_pages directly so that it can return page-aligned blocks
19 * and keeps a linked list of such pages and their orders. These
20 * objects are detected in kfree() by their page alignment.
21 *
22 * SLAB is emulated on top of SLOB by simply calling constructors and
23 * destructors for every SLAB allocation. Objects are returned with
Christoph Lameter5af60832007-05-06 14:49:56 -070024 * the 8-byte alignment unless the SLAB_HWCACHE_ALIGN flag is
Matt Mackall10cef602006-01-08 01:01:45 -080025 * set, in which case the low-level allocator will fragment blocks to
26 * create the proper alignment. Again, objects of page-size or greater
27 * are allocated by calling __get_free_pages. As SLAB objects know
28 * their size, no separate size bookkeeping is necessary and there is
29 * essentially no allocation space overhead.
30 */
31
Matt Mackall10cef602006-01-08 01:01:45 -080032#include <linux/slab.h>
33#include <linux/mm.h>
34#include <linux/cache.h>
35#include <linux/init.h>
36#include <linux/module.h>
37#include <linux/timer.h>
38
39struct slob_block {
40 int units;
41 struct slob_block *next;
42};
43typedef struct slob_block slob_t;
44
45#define SLOB_UNIT sizeof(slob_t)
46#define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
47#define SLOB_ALIGN L1_CACHE_BYTES
48
49struct bigblock {
50 int order;
51 void *pages;
52 struct bigblock *next;
53};
54typedef struct bigblock bigblock_t;
55
56static slob_t arena = { .next = &arena, .units = 1 };
57static slob_t *slobfree = &arena;
58static bigblock_t *bigblocks;
59static DEFINE_SPINLOCK(slob_lock);
60static DEFINE_SPINLOCK(block_lock);
61
62static void slob_free(void *b, int size);
Dimitri Gorokhovikbcb4ddb2006-12-29 16:48:28 -080063static void slob_timer_cbk(void);
64
Matt Mackall10cef602006-01-08 01:01:45 -080065
66static void *slob_alloc(size_t size, gfp_t gfp, int align)
67{
68 slob_t *prev, *cur, *aligned = 0;
69 int delta = 0, units = SLOB_UNITS(size);
70 unsigned long flags;
71
72 spin_lock_irqsave(&slob_lock, flags);
73 prev = slobfree;
74 for (cur = prev->next; ; prev = cur, cur = cur->next) {
75 if (align) {
76 aligned = (slob_t *)ALIGN((unsigned long)cur, align);
77 delta = aligned - cur;
78 }
79 if (cur->units >= units + delta) { /* room enough? */
80 if (delta) { /* need to fragment head to align? */
81 aligned->units = cur->units - delta;
82 aligned->next = cur->next;
83 cur->next = aligned;
84 cur->units = delta;
85 prev = cur;
86 cur = aligned;
87 }
88
89 if (cur->units == units) /* exact fit? */
90 prev->next = cur->next; /* unlink */
91 else { /* fragment */
92 prev->next = cur + units;
93 prev->next->units = cur->units - units;
94 prev->next->next = cur->next;
95 cur->units = units;
96 }
97
98 slobfree = prev;
99 spin_unlock_irqrestore(&slob_lock, flags);
100 return cur;
101 }
102 if (cur == slobfree) {
103 spin_unlock_irqrestore(&slob_lock, flags);
104
105 if (size == PAGE_SIZE) /* trying to shrink arena? */
106 return 0;
107
108 cur = (slob_t *)__get_free_page(gfp);
109 if (!cur)
110 return 0;
111
112 slob_free(cur, PAGE_SIZE);
113 spin_lock_irqsave(&slob_lock, flags);
114 cur = slobfree;
115 }
116 }
117}
118
119static void slob_free(void *block, int size)
120{
121 slob_t *cur, *b = (slob_t *)block;
122 unsigned long flags;
123
124 if (!block)
125 return;
126
127 if (size)
128 b->units = SLOB_UNITS(size);
129
130 /* Find reinsertion point */
131 spin_lock_irqsave(&slob_lock, flags);
132 for (cur = slobfree; !(b > cur && b < cur->next); cur = cur->next)
133 if (cur >= cur->next && (b > cur || b < cur->next))
134 break;
135
136 if (b + b->units == cur->next) {
137 b->units += cur->next->units;
138 b->next = cur->next->next;
139 } else
140 b->next = cur->next;
141
142 if (cur + cur->units == b) {
143 cur->units += b->units;
144 cur->next = b->next;
145 } else
146 cur->next = b;
147
148 slobfree = cur;
149
150 spin_unlock_irqrestore(&slob_lock, flags);
151}
152
Christoph Lameter2e892f42006-12-13 00:34:23 -0800153void *__kmalloc(size_t size, gfp_t gfp)
Matt Mackall10cef602006-01-08 01:01:45 -0800154{
155 slob_t *m;
156 bigblock_t *bb;
157 unsigned long flags;
158
159 if (size < PAGE_SIZE - SLOB_UNIT) {
160 m = slob_alloc(size + SLOB_UNIT, gfp, 0);
161 return m ? (void *)(m + 1) : 0;
162 }
163
164 bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
165 if (!bb)
166 return 0;
167
Akinobu Mita4ab688c2007-05-06 14:50:19 -0700168 bb->order = get_order(size);
Matt Mackall10cef602006-01-08 01:01:45 -0800169 bb->pages = (void *)__get_free_pages(gfp, bb->order);
170
171 if (bb->pages) {
172 spin_lock_irqsave(&block_lock, flags);
173 bb->next = bigblocks;
174 bigblocks = bb;
175 spin_unlock_irqrestore(&block_lock, flags);
176 return bb->pages;
177 }
178
179 slob_free(bb, sizeof(bigblock_t));
180 return 0;
181}
Christoph Lameter2e892f42006-12-13 00:34:23 -0800182EXPORT_SYMBOL(__kmalloc);
Matt Mackall10cef602006-01-08 01:01:45 -0800183
Pekka Enbergfd76bab2007-05-06 14:48:40 -0700184/**
185 * krealloc - reallocate memory. The contents will remain unchanged.
186 *
187 * @p: object to reallocate memory for.
188 * @new_size: how many bytes of memory are required.
189 * @flags: the type of memory to allocate.
190 *
191 * The contents of the object pointed to are preserved up to the
192 * lesser of the new and old sizes. If @p is %NULL, krealloc()
193 * behaves exactly like kmalloc(). If @size is 0 and @p is not a
194 * %NULL pointer, the object pointed to is freed.
195 */
196void *krealloc(const void *p, size_t new_size, gfp_t flags)
197{
198 void *ret;
199
200 if (unlikely(!p))
201 return kmalloc_track_caller(new_size, flags);
202
203 if (unlikely(!new_size)) {
204 kfree(p);
205 return NULL;
206 }
207
208 ret = kmalloc_track_caller(new_size, flags);
209 if (ret) {
210 memcpy(ret, p, min(new_size, ksize(p)));
211 kfree(p);
212 }
213 return ret;
214}
215EXPORT_SYMBOL(krealloc);
216
Matt Mackall10cef602006-01-08 01:01:45 -0800217void kfree(const void *block)
218{
219 bigblock_t *bb, **last = &bigblocks;
220 unsigned long flags;
221
222 if (!block)
223 return;
224
225 if (!((unsigned long)block & (PAGE_SIZE-1))) {
226 /* might be on the big block list */
227 spin_lock_irqsave(&block_lock, flags);
228 for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {
229 if (bb->pages == block) {
230 *last = bb->next;
231 spin_unlock_irqrestore(&block_lock, flags);
232 free_pages((unsigned long)block, bb->order);
233 slob_free(bb, sizeof(bigblock_t));
234 return;
235 }
236 }
237 spin_unlock_irqrestore(&block_lock, flags);
238 }
239
240 slob_free((slob_t *)block - 1, 0);
241 return;
242}
243
244EXPORT_SYMBOL(kfree);
245
Pekka Enbergfd76bab2007-05-06 14:48:40 -0700246size_t ksize(const void *block)
Matt Mackall10cef602006-01-08 01:01:45 -0800247{
248 bigblock_t *bb;
249 unsigned long flags;
250
251 if (!block)
252 return 0;
253
254 if (!((unsigned long)block & (PAGE_SIZE-1))) {
255 spin_lock_irqsave(&block_lock, flags);
256 for (bb = bigblocks; bb; bb = bb->next)
257 if (bb->pages == block) {
258 spin_unlock_irqrestore(&slob_lock, flags);
259 return PAGE_SIZE << bb->order;
260 }
261 spin_unlock_irqrestore(&block_lock, flags);
262 }
263
264 return ((slob_t *)block - 1)->units * SLOB_UNIT;
265}
266
267struct kmem_cache {
268 unsigned int size, align;
269 const char *name;
270 void (*ctor)(void *, struct kmem_cache *, unsigned long);
271 void (*dtor)(void *, struct kmem_cache *, unsigned long);
272};
273
274struct kmem_cache *kmem_cache_create(const char *name, size_t size,
275 size_t align, unsigned long flags,
276 void (*ctor)(void*, struct kmem_cache *, unsigned long),
277 void (*dtor)(void*, struct kmem_cache *, unsigned long))
278{
279 struct kmem_cache *c;
280
281 c = slob_alloc(sizeof(struct kmem_cache), flags, 0);
282
283 if (c) {
284 c->name = name;
285 c->size = size;
286 c->ctor = ctor;
287 c->dtor = dtor;
288 /* ignore alignment unless it's forced */
Christoph Lameter5af60832007-05-06 14:49:56 -0700289 c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
Matt Mackall10cef602006-01-08 01:01:45 -0800290 if (c->align < align)
291 c->align = align;
Akinobu Mitabc0055a2007-05-06 14:49:52 -0700292 } else if (flags & SLAB_PANIC)
293 panic("Cannot create slab cache %s\n", name);
Matt Mackall10cef602006-01-08 01:01:45 -0800294
295 return c;
296}
297EXPORT_SYMBOL(kmem_cache_create);
298
Alexey Dobriyan133d2052006-09-27 01:49:41 -0700299void kmem_cache_destroy(struct kmem_cache *c)
Matt Mackall10cef602006-01-08 01:01:45 -0800300{
301 slob_free(c, sizeof(struct kmem_cache));
Matt Mackall10cef602006-01-08 01:01:45 -0800302}
303EXPORT_SYMBOL(kmem_cache_destroy);
304
305void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
306{
307 void *b;
308
309 if (c->size < PAGE_SIZE)
310 b = slob_alloc(c->size, flags, c->align);
311 else
Akinobu Mita4ab688c2007-05-06 14:50:19 -0700312 b = (void *)__get_free_pages(flags, get_order(c->size));
Matt Mackall10cef602006-01-08 01:01:45 -0800313
314 if (c->ctor)
315 c->ctor(b, c, SLAB_CTOR_CONSTRUCTOR);
316
317 return b;
318}
319EXPORT_SYMBOL(kmem_cache_alloc);
320
Pekka Enberga8c0f9a2006-03-25 03:06:42 -0800321void *kmem_cache_zalloc(struct kmem_cache *c, gfp_t flags)
322{
323 void *ret = kmem_cache_alloc(c, flags);
324 if (ret)
325 memset(ret, 0, c->size);
326
327 return ret;
328}
329EXPORT_SYMBOL(kmem_cache_zalloc);
330
Matt Mackall10cef602006-01-08 01:01:45 -0800331void kmem_cache_free(struct kmem_cache *c, void *b)
332{
333 if (c->dtor)
334 c->dtor(b, c, 0);
335
336 if (c->size < PAGE_SIZE)
337 slob_free(b, c->size);
338 else
Akinobu Mita4ab688c2007-05-06 14:50:19 -0700339 free_pages((unsigned long)b, get_order(c->size));
Matt Mackall10cef602006-01-08 01:01:45 -0800340}
341EXPORT_SYMBOL(kmem_cache_free);
342
343unsigned int kmem_cache_size(struct kmem_cache *c)
344{
345 return c->size;
346}
347EXPORT_SYMBOL(kmem_cache_size);
348
349const char *kmem_cache_name(struct kmem_cache *c)
350{
351 return c->name;
352}
353EXPORT_SYMBOL(kmem_cache_name);
354
355static struct timer_list slob_timer = TIMER_INITIALIZER(
Dimitri Gorokhovikbcb4ddb2006-12-29 16:48:28 -0800356 (void (*)(unsigned long))slob_timer_cbk, 0, 0);
Matt Mackall10cef602006-01-08 01:01:45 -0800357
Christoph Lameter2e892f42006-12-13 00:34:23 -0800358int kmem_cache_shrink(struct kmem_cache *d)
359{
360 return 0;
361}
362EXPORT_SYMBOL(kmem_cache_shrink);
363
Christoph Lameter55935a32006-12-13 00:34:24 -0800364int kmem_ptr_validate(struct kmem_cache *a, const void *b)
Christoph Lameter2e892f42006-12-13 00:34:23 -0800365{
366 return 0;
367}
368
Dimitri Gorokhovikbcb4ddb2006-12-29 16:48:28 -0800369void __init kmem_cache_init(void)
370{
371 slob_timer_cbk();
372}
373
374static void slob_timer_cbk(void)
Matt Mackall10cef602006-01-08 01:01:45 -0800375{
376 void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);
377
378 if (p)
379 free_page((unsigned long)p);
380
381 mod_timer(&slob_timer, jiffies + HZ);
382}