mm/slob.c

   1 /*
   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
  32 #include <linux/config.h>
  33 #include <linux/slab.h>
  34 #include <linux/mm.h>
  35 #include <linux/cache.h>
  36 #include <linux/init.h>
  37 #include <linux/module.h>
  38 #include <linux/timer.h>
  39
  40 struct slob_block {
  41         int units;
  42         struct slob_block *next;
  43 };
  44 typedef struct slob_block slob_t;
  45
  46 #define SLOB_UNIT sizeof(slob_t)
  47 #define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
  48 #define SLOB_ALIGN L1_CACHE_BYTES
  49
  50 struct bigblock {
  51         int order;
  52         void *pages;
  53         struct bigblock *next;
  54 };
  55 typedef struct bigblock bigblock_t;
  56
  57 static slob_t arena = { .next = &arena, .units = 1 };
  58 static slob_t *slobfree = &arena;
  59 static bigblock_t *bigblocks;
  60 static DEFINE_SPINLOCK(slob_lock);
  61 static DEFINE_SPINLOCK(block_lock);
  62
  63 static void slob_free(void *b, int size);
  64
  65 static void *slob_alloc(size_t size, gfp_t gfp, int align)
  66 {
  67         slob_t *prev, *cur, *aligned = 0;
  68         int delta = 0, units = SLOB_UNITS(size);
  69         unsigned long flags;
  70
  71         spin_lock_irqsave(&slob_lock, flags);
  72         prev = slobfree;
  73         for (cur = prev->next; ; prev = cur, cur = cur->next) {
  74                 if (align) {
  75                         aligned = (slob_t *)ALIGN((unsigned long)cur, align);
  76                         delta = aligned - cur;
  77                 }
  78                 if (cur->units >= units + delta) { /* room enough? */
  79                         if (delta) { /* need to fragment head to align? */
  80                                 aligned->units = cur->units - delta;
  81                                 aligned->next = cur->next;
  82                                 cur->next = aligned;
  83                                 cur->units = delta;
  84                                 prev = cur;
  85                                 cur = aligned;
  86                         }
  87
  88                         if (cur->units == units) /* exact fit? */
  89                                 prev->next = cur->next; /* unlink */
  90                         else { /* fragment */
  91                                 prev->next = cur + units;
  92                                 prev->next->units = cur->units - units;
  93                                 prev->next->next = cur->next;
  94                                 cur->units = units;
  95                         }
  96
  97                         slobfree = prev;
  98                         spin_unlock_irqrestore(&slob_lock, flags);
  99                         return cur;
 100                 }
 101                 if (cur == slobfree) {
 102                         spin_unlock_irqrestore(&slob_lock, flags);
 103
 104                         if (size == PAGE_SIZE) /* trying to shrink arena? */
 105                                 return 0;
 106
 107                         cur = (slob_t *)__get_free_page(gfp);
 108                         if (!cur)
 109                                 return 0;
 110
 111                         slob_free(cur, PAGE_SIZE);
 112                         spin_lock_irqsave(&slob_lock, flags);
 113                         cur = slobfree;
 114                 }
 115         }
 116 }
 117
 118 static void slob_free(void *block, int size)
 119 {
 120         slob_t *cur, *b = (slob_t *)block;
 121         unsigned long flags;
 122
 123         if (!block)
 124                 return;
 125
 126         if (size)
 127                 b->units = SLOB_UNITS(size);
 128
 129         /* Find reinsertion point */
 130         spin_lock_irqsave(&slob_lock, flags);
 131         for (cur = slobfree; !(b > cur && b < cur->next); cur = cur->next)
 132                 if (cur >= cur->next && (b > cur || b < cur->next))
 133                         break;
 134
 135         if (b + b->units == cur->next) {
 136                 b->units += cur->next->units;
 137                 b->next = cur->next->next;
 138         } else
 139                 b->next = cur->next;
 140
 141         if (cur + cur->units == b) {
 142                 cur->units += b->units;
 143                 cur->next = b->next;
 144         } else
 145                 cur->next = b;
 146
 147         slobfree = cur;
 148
 149         spin_unlock_irqrestore(&slob_lock, flags);
 150 }
 151
 152 static int FASTCALL(find_order(int size));
 153 static int fastcall find_order(int size)
 154 {
 155         int order = 0;
 156         for ( ; size > 4096 ; size >>=1)
 157                 order++;
 158         return order;
 159 }
 160
 161 void *kmalloc(size_t size, gfp_t gfp)
 162 {
 163         slob_t *m;
 164         bigblock_t *bb;
 165         unsigned long flags;
 166
 167         if (size < PAGE_SIZE - SLOB_UNIT) {
 168                 m = slob_alloc(size + SLOB_UNIT, gfp, 0);
 169                 return m ? (void *)(m + 1) : 0;
 170         }
 171
 172         bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
 173         if (!bb)
 174                 return 0;
 175
 176         bb->order = find_order(size);
 177         bb->pages = (void *)__get_free_pages(gfp, bb->order);
 178
 179         if (bb->pages) {
 180                 spin_lock_irqsave(&block_lock, flags);
 181                 bb->next = bigblocks;
 182                 bigblocks = bb;
 183                 spin_unlock_irqrestore(&block_lock, flags);
 184                 return bb->pages;
 185         }
 186
 187         slob_free(bb, sizeof(bigblock_t));
 188         return 0;
 189 }
 190
 191 EXPORT_SYMBOL(kmalloc);
 192
 193 void 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
 220 EXPORT_SYMBOL(kfree);
 221
 222 unsigned 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
 243 struct 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
 250 struct 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 }
 272 EXPORT_SYMBOL(kmem_cache_create);
 273
 274 int kmem_cache_destroy(struct kmem_cache *c)
 275 {
 276         slob_free(c, sizeof(struct kmem_cache));
 277         return 0;
 278 }
 279 EXPORT_SYMBOL(kmem_cache_destroy);
 280
 281 void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
 282 {
 283         void *b;
 284
 285         if (c->size < PAGE_SIZE)
 286                 b = slob_alloc(c->size, flags, c->align);
 287         else
 288                 b = (void *)__get_free_pages(flags, find_order(c->size));
 289
 290         if (c->ctor)
 291                 c->ctor(b, c, SLAB_CTOR_CONSTRUCTOR);
 292
 293         return b;
 294 }
 295 EXPORT_SYMBOL(kmem_cache_alloc);
 296
 297 void kmem_cache_free(struct kmem_cache *c, void *b)
 298 {
 299         if (c->dtor)
 300                 c->dtor(b, c, 0);
 301
 302         if (c->size < PAGE_SIZE)
 303                 slob_free(b, c->size);
 304         else
 305                 free_pages((unsigned long)b, find_order(c->size));
 306 }
 307 EXPORT_SYMBOL(kmem_cache_free);
 308
 309 unsigned int kmem_cache_size(struct kmem_cache *c)
 310 {
 311         return c->size;
 312 }
 313 EXPORT_SYMBOL(kmem_cache_size);
 314
 315 const char *kmem_cache_name(struct kmem_cache *c)
 316 {
 317         return c->name;
 318 }
 319 EXPORT_SYMBOL(kmem_cache_name);
 320
 321 static struct timer_list slob_timer = TIMER_INITIALIZER(
 322         (void (*)(unsigned long))kmem_cache_init, 0, 0);
 323
 324 void kmem_cache_init(void)
 325 {
 326         void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);
 327
 328         if (p)
 329                 free_page((unsigned long)p);
 330
 331         mod_timer(&slob_timer, jiffies + HZ);
 332 }
 333
 334 atomic_t slab_reclaim_pages = ATOMIC_INIT(0);
 335 EXPORT_SYMBOL(slab_reclaim_pages);
 336
 337 #ifdef CONFIG_SMP
 338
 339 void *__alloc_percpu(size_t size)
 340 {
 341         int i;
 342         struct percpu_data *pdata = kmalloc(sizeof (*pdata), GFP_KERNEL);
 343
 344         if (!pdata)
 345                 return NULL;
 346
 347         for (i = 0; i < NR_CPUS; i++) {
 348                 if (!cpu_possible(i))
 349                         continue;
 350                 pdata->ptrs[i] = kmalloc(size, GFP_KERNEL);
 351                 if (!pdata->ptrs[i])
 352                         goto unwind_oom;
 353                 memset(pdata->ptrs[i], 0, size);
 354         }
 355
 356         /* Catch derefs w/o wrappers */
 357         return (void *) (~(unsigned long) pdata);
 358
 359 unwind_oom:
 360         while (--i >= 0) {
 361                 if (!cpu_possible(i))
 362                         continue;
 363                 kfree(pdata->ptrs[i]);
 364         }
 365         kfree(pdata);
 366         return NULL;
 367 }
 368 EXPORT_SYMBOL(__alloc_percpu);
 369
 370 void
 371 free_percpu(const void *objp)
 372 {
 373         int i;
 374         struct percpu_data *p = (struct percpu_data *) (~(unsigned long) objp);
 375
 376         for (i = 0; i < NR_CPUS; i++) {
 377                 if (!cpu_possible(i))
 378                         continue;
 379                 kfree(p->ptrs[i]);
 380         }
 381         kfree(p);
 382 }
 383 EXPORT_SYMBOL(free_percpu);
 384
 385 #endif