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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
24 * the 8-byte alignment unless the SLAB_MUST_HWCACHE_ALIGN flag is
25 * 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
153static int FASTCALL(find_order(int size));
154static int fastcall find_order(int size)
155{
156 int order = 0;
157 for ( ; size > 4096 ; size >>=1)
158 order++;
159 return order;
160}
161
Christoph Lameter2e892f42006-12-13 00:34:23 -0800162void *__kmalloc(size_t size, gfp_t gfp)
Matt Mackall10cef602006-01-08 01:01:45 -0800163{
164 slob_t *m;
165 bigblock_t *bb;
166 unsigned long flags;
167
168 if (size < PAGE_SIZE - SLOB_UNIT) {
169 m = slob_alloc(size + SLOB_UNIT, gfp, 0);
170 return m ? (void *)(m + 1) : 0;
171 }
172
173 bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
174 if (!bb)
175 return 0;
176
177 bb->order = find_order(size);
178 bb->pages = (void *)__get_free_pages(gfp, bb->order);
179
180 if (bb->pages) {
181 spin_lock_irqsave(&block_lock, flags);
182 bb->next = bigblocks;
183 bigblocks = bb;
184 spin_unlock_irqrestore(&block_lock, flags);
185 return bb->pages;
186 }
187
188 slob_free(bb, sizeof(bigblock_t));
189 return 0;
190}
Christoph Lameter2e892f42006-12-13 00:34:23 -0800191EXPORT_SYMBOL(__kmalloc);
Matt Mackall10cef602006-01-08 01:01:45 -0800192
193void kfree(const void *block)
194{
195 bigblock_t *bb, **last = &bigblocks;
196 unsigned long flags;
197
198 if (!block)
199 return;
200
201 if (!((unsigned long)block & (PAGE_SIZE-1))) {
202 /* might be on the big block list */
203 spin_lock_irqsave(&block_lock, flags);
204 for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {
205 if (bb->pages == block) {
206 *last = bb->next;
207 spin_unlock_irqrestore(&block_lock, flags);
208 free_pages((unsigned long)block, bb->order);
209 slob_free(bb, sizeof(bigblock_t));
210 return;
211 }
212 }
213 spin_unlock_irqrestore(&block_lock, flags);
214 }
215
216 slob_free((slob_t *)block - 1, 0);
217 return;
218}
219
220EXPORT_SYMBOL(kfree);
221
222unsigned int ksize(const void *block)
223{
224 bigblock_t *bb;
225 unsigned long flags;
226
227 if (!block)
228 return 0;
229
230 if (!((unsigned long)block & (PAGE_SIZE-1))) {
231 spin_lock_irqsave(&block_lock, flags);
232 for (bb = bigblocks; bb; bb = bb->next)
233 if (bb->pages == block) {
234 spin_unlock_irqrestore(&slob_lock, flags);
235 return PAGE_SIZE << bb->order;
236 }
237 spin_unlock_irqrestore(&block_lock, flags);
238 }
239
240 return ((slob_t *)block - 1)->units * SLOB_UNIT;
241}
242
243struct kmem_cache {
244 unsigned int size, align;
245 const char *name;
246 void (*ctor)(void *, struct kmem_cache *, unsigned long);
247 void (*dtor)(void *, struct kmem_cache *, unsigned long);
248};
249
250struct kmem_cache *kmem_cache_create(const char *name, size_t size,
251 size_t align, unsigned long flags,
252 void (*ctor)(void*, struct kmem_cache *, unsigned long),
253 void (*dtor)(void*, struct kmem_cache *, unsigned long))
254{
255 struct kmem_cache *c;
256
257 c = slob_alloc(sizeof(struct kmem_cache), flags, 0);
258
259 if (c) {
260 c->name = name;
261 c->size = size;
262 c->ctor = ctor;
263 c->dtor = dtor;
264 /* ignore alignment unless it's forced */
265 c->align = (flags & SLAB_MUST_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
266 if (c->align < align)
267 c->align = align;
268 }
269
270 return c;
271}
272EXPORT_SYMBOL(kmem_cache_create);
273
Alexey Dobriyan133d2052006-09-27 01:49:41 -0700274void kmem_cache_destroy(struct kmem_cache *c)
Matt Mackall10cef602006-01-08 01:01:45 -0800275{
276 slob_free(c, sizeof(struct kmem_cache));
Matt Mackall10cef602006-01-08 01:01:45 -0800277}
278EXPORT_SYMBOL(kmem_cache_destroy);
279
280void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
281{
282 void *b;
283
284 if (c->size < PAGE_SIZE)
285 b = slob_alloc(c->size, flags, c->align);
286 else
287 b = (void *)__get_free_pages(flags, find_order(c->size));
288
289 if (c->ctor)
290 c->ctor(b, c, SLAB_CTOR_CONSTRUCTOR);
291
292 return b;
293}
294EXPORT_SYMBOL(kmem_cache_alloc);
295
Pekka Enberga8c0f9a2006-03-25 03:06:42 -0800296void *kmem_cache_zalloc(struct kmem_cache *c, gfp_t flags)
297{
298 void *ret = kmem_cache_alloc(c, flags);
299 if (ret)
300 memset(ret, 0, c->size);
301
302 return ret;
303}
304EXPORT_SYMBOL(kmem_cache_zalloc);
305
Matt Mackall10cef602006-01-08 01:01:45 -0800306void kmem_cache_free(struct kmem_cache *c, void *b)
307{
308 if (c->dtor)
309 c->dtor(b, c, 0);
310
311 if (c->size < PAGE_SIZE)
312 slob_free(b, c->size);
313 else
314 free_pages((unsigned long)b, find_order(c->size));
315}
316EXPORT_SYMBOL(kmem_cache_free);
317
318unsigned int kmem_cache_size(struct kmem_cache *c)
319{
320 return c->size;
321}
322EXPORT_SYMBOL(kmem_cache_size);
323
324const char *kmem_cache_name(struct kmem_cache *c)
325{
326 return c->name;
327}
328EXPORT_SYMBOL(kmem_cache_name);
329
330static struct timer_list slob_timer = TIMER_INITIALIZER(
Dimitri Gorokhovikbcb4ddb2006-12-29 16:48:28 -0800331 (void (*)(unsigned long))slob_timer_cbk, 0, 0);
Matt Mackall10cef602006-01-08 01:01:45 -0800332
Christoph Lameter2e892f42006-12-13 00:34:23 -0800333int kmem_cache_shrink(struct kmem_cache *d)
334{
335 return 0;
336}
337EXPORT_SYMBOL(kmem_cache_shrink);
338
Christoph Lameter55935a32006-12-13 00:34:24 -0800339int kmem_ptr_validate(struct kmem_cache *a, const void *b)
Christoph Lameter2e892f42006-12-13 00:34:23 -0800340{
341 return 0;
342}
343
Dimitri Gorokhovikbcb4ddb2006-12-29 16:48:28 -0800344void __init kmem_cache_init(void)
345{
346 slob_timer_cbk();
347}
348
349static void slob_timer_cbk(void)
Matt Mackall10cef602006-01-08 01:01:45 -0800350{
351 void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);
352
353 if (p)
354 free_page((unsigned long)p);
355
356 mod_timer(&slob_timer, jiffies + HZ);
357}