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. 32 * These objects are detected in kfree() because PageSlab() 33 * is false for them. 34 * 35 * SLAB is emulated on top of SLOB by simply calling constructors and 36 * destructors for every SLAB allocation. Objects are returned with the 37 * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which 38 * case the low-level allocator will fragment blocks to create the proper 39 * alignment. Again, objects of page-size or greater are allocated by 40 * calling alloc_pages(). As SLAB objects know their size, no separate 41 * size bookkeeping is necessary and there is essentially no allocation 42 * space overhead, and compound pages aren't needed for multi-page 43 * allocations. 44 * 45 * NUMA support in SLOB is fairly simplistic, pushing most of the real 46 * logic down to the page allocator, and simply doing the node accounting 47 * on the upper levels. In the event that a node id is explicitly 48 * provided, alloc_pages_exact_node() with the specified node id is used 49 * instead. The common case (or when the node id isn't explicitly provided) 50 * will default to the current node, as per numa_node_id(). 51 * 52 * Node aware pages are still inserted in to the global freelist, and 53 * these are scanned for by matching against the node id encoded in the 54 * page flags. As a result, block allocations that can be satisfied from 55 * the freelist will only be done so on pages residing on the same node, 56 * in order to prevent random node placement. 57 */ 58 59#include <linux/kernel.h> 60#include <linux/slab.h> 61 62#include <linux/mm.h> 63#include <linux/swap.h> /* struct reclaim_state */ 64#include <linux/cache.h> 65#include <linux/init.h> 66#include <linux/export.h> 67#include <linux/rcupdate.h> 68#include <linux/list.h> 69#include <linux/kmemleak.h> 70 71#include <trace/events/kmem.h> 72 73#include <linux/atomic.h> 74 75#include "slab.h" 76/* 77 * slob_block has a field 'units', which indicates size of block if +ve, 78 * or offset of next block if -ve (in SLOB_UNITs). 79 * 80 * Free blocks of size 1 unit simply contain the offset of the next block. 81 * Those with larger size contain their size in the first SLOB_UNIT of 82 * memory, and the offset of the next free block in the second SLOB_UNIT. 83 */ 84#if PAGE_SIZE <= (32767 * 2) 85typedef s16 slobidx_t; 86#else 87typedef s32 slobidx_t; 88#endif 89 90struct slob_block { 91 slobidx_t units; 92}; 93typedef struct slob_block slob_t; 94 95/* 96 * All partially free slob pages go on these lists. 97 */ 98#define SLOB_BREAK1 256 99#define SLOB_BREAK2 1024 100static LIST_HEAD(free_slob_small); 101static LIST_HEAD(free_slob_medium); 102static LIST_HEAD(free_slob_large); 103 104/* 105 * slob_page_free: true for pages on free_slob_pages list. 106 */ 107static inline int slob_page_free(struct page *sp) 108{ 109 return PageSlobFree(sp); 110} 111 112static void set_slob_page_free(struct page *sp, struct list_head *list) 113{ 114 list_add(&sp->lru, list); 115 __SetPageSlobFree(sp); 116} 117 118static inline void clear_slob_page_free(struct page *sp) 119{ 120 list_del(&sp->lru); 121 __ClearPageSlobFree(sp); 122} 123 124#define SLOB_UNIT sizeof(slob_t) 125#define SLOB_UNITS(size) DIV_ROUND_UP(size, SLOB_UNIT) 126 127/* 128 * struct slob_rcu is inserted at the tail of allocated slob blocks, which 129 * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free 130 * the block using call_rcu. 131 */ 132struct slob_rcu { 133 struct rcu_head head; 134 int size; 135}; 136 137/* 138 * slob_lock protects all slob allocator structures. 139 */ 140static DEFINE_SPINLOCK(slob_lock); 141 142/* 143 * Encode the given size and next info into a free slob block s. 144 */ 145static void set_slob(slob_t *s, slobidx_t size, slob_t *next) 146{ 147 slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK); 148 slobidx_t offset = next - base; 149 150 if (size > 1) { 151 s[0].units = size; 152 s[1].units = offset; 153 } else 154 s[0].units = -offset; 155} 156 157/* 158 * Return the size of a slob block. 159 */ 160static slobidx_t slob_units(slob_t *s) 161{ 162 if (s->units > 0) 163 return s->units; 164 return 1; 165} 166 167/* 168 * Return the next free slob block pointer after this one. 169 */ 170static slob_t *slob_next(slob_t *s) 171{ 172 slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK); 173 slobidx_t next; 174 175 if (s[0].units < 0) 176 next = -s[0].units; 177 else 178 next = s[1].units; 179 return base+next; 180} 181 182/* 183 * Returns true if s is the last free block in its page. 184 */ 185static int slob_last(slob_t *s) 186{ 187 return !((unsigned long)slob_next(s) & ~PAGE_MASK); 188} 189 190static void *slob_new_pages(gfp_t gfp, int order, int node) 191{ 192 void *page; 193 194#ifdef CONFIG_NUMA 195 if (node != NUMA_NO_NODE) 196 page = alloc_pages_exact_node(node, gfp, order); 197 else 198#endif 199 page = alloc_pages(gfp, order); 200 201 if (!page) 202 return NULL; 203 204 return page_address(page); 205} 206 207static void slob_free_pages(void *b, int order) 208{ 209 if (current->reclaim_state) 210 current->reclaim_state->reclaimed_slab += 1 << order; 211 free_pages((unsigned long)b, order); 212} 213 214/* 215 * Allocate a slob block within a given slob_page sp. 216 */ 217static void *slob_page_alloc(struct page *sp, size_t size, int align) 218{ 219 slob_t *prev, *cur, *aligned = NULL; 220 int delta = 0, units = SLOB_UNITS(size); 221 222 for (prev = NULL, cur = sp->freelist; ; prev = cur, cur = slob_next(cur)) { 223 slobidx_t avail = slob_units(cur); 224 225 if (align) { 226 aligned = (slob_t *)ALIGN((unsigned long)cur, align); 227 delta = aligned - cur; 228 } 229 if (avail >= units + delta) { /* room enough? */ 230 slob_t *next; 231 232 if (delta) { /* need to fragment head to align? */ 233 next = slob_next(cur); 234 set_slob(aligned, avail - delta, next); 235 set_slob(cur, delta, aligned); 236 prev = cur; 237 cur = aligned; 238 avail = slob_units(cur); 239 } 240 241 next = slob_next(cur); 242 if (avail == units) { /* exact fit? unlink. */ 243 if (prev) 244 set_slob(prev, slob_units(prev), next); 245 else 246 sp->freelist = next; 247 } else { /* fragment */ 248 if (prev) 249 set_slob(prev, slob_units(prev), cur + units); 250 else 251 sp->freelist = cur + units; 252 set_slob(cur + units, avail - units, next); 253 } 254 255 sp->units -= units; 256 if (!sp->units) 257 clear_slob_page_free(sp); 258 return cur; 259 } 260 if (slob_last(cur)) 261 return NULL; 262 } 263} 264 265/* 266 * slob_alloc: entry point into the slob allocator. 267 */ 268static void *slob_alloc(size_t size, gfp_t gfp, int align, int node) 269{ 270 struct page *sp; 271 struct list_head *prev; 272 struct list_head *slob_list; 273 slob_t *b = NULL; 274 unsigned long flags; 275 276 if (size < SLOB_BREAK1) 277 slob_list = &free_slob_small; 278 else if (size < SLOB_BREAK2) 279 slob_list = &free_slob_medium; 280 else 281 slob_list = &free_slob_large; 282 283 spin_lock_irqsave(&slob_lock, flags); 284 /* Iterate through each partially free page, try to find room */ 285 list_for_each_entry(sp, slob_list, lru) { 286#ifdef CONFIG_NUMA 287 /* 288 * If there's a node specification, search for a partial 289 * page with a matching node id in the freelist. 290 */ 291 if (node != NUMA_NO_NODE && page_to_nid(sp) != node) 292 continue; 293#endif 294 /* Enough room on this page? */ 295 if (sp->units < SLOB_UNITS(size)) 296 continue; 297 298 /* Attempt to alloc */ 299 prev = sp->lru.prev; 300 b = slob_page_alloc(sp, size, align); 301 if (!b) 302 continue; 303 304 /* Improve fragment distribution and reduce our average 305 * search time by starting our next search here. (see 306 * Knuth vol 1, sec 2.5, pg 449) */ 307 if (prev != slob_list->prev && 308 slob_list->next != prev->next) 309 list_move_tail(slob_list, prev->next); 310 break; 311 } 312 spin_unlock_irqrestore(&slob_lock, flags); 313 314 /* Not enough space: must allocate a new page */ 315 if (!b) { 316 b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node); 317 if (!b) 318 return NULL; 319 sp = virt_to_page(b); 320 __SetPageSlab(sp); 321 322 spin_lock_irqsave(&slob_lock, flags); 323 sp->units = SLOB_UNITS(PAGE_SIZE); 324 sp->freelist = b; 325 INIT_LIST_HEAD(&sp->lru); 326 set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE)); 327 set_slob_page_free(sp, slob_list); 328 b = slob_page_alloc(sp, size, align); 329 BUG_ON(!b); 330 spin_unlock_irqrestore(&slob_lock, flags); 331 } 332 if (unlikely((gfp & __GFP_ZERO) && b)) 333 memset(b, 0, size); 334 return b; 335} 336 337/* 338 * slob_free: entry point into the slob allocator. 339 */ 340static void slob_free(void *block, int size) 341{ 342 struct page *sp; 343 slob_t *prev, *next, *b = (slob_t *)block; 344 slobidx_t units; 345 unsigned long flags; 346 struct list_head *slob_list; 347 348 if (unlikely(ZERO_OR_NULL_PTR(block))) 349 return; 350 BUG_ON(!size); 351 352 sp = virt_to_page(block); 353 units = SLOB_UNITS(size); 354 355 spin_lock_irqsave(&slob_lock, flags); 356 357 if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) { 358 /* Go directly to page allocator. Do not pass slob allocator */ 359 if (slob_page_free(sp)) 360 clear_slob_page_free(sp); 361 spin_unlock_irqrestore(&slob_lock, flags); 362 __ClearPageSlab(sp); 363 page_mapcount_reset(sp); 364 slob_free_pages(b, 0); 365 return; 366 } 367 368 if (!slob_page_free(sp)) { 369 /* This slob page is about to become partially free. Easy! */ 370 sp->units = units; 371 sp->freelist = b; 372 set_slob(b, units, 373 (void *)((unsigned long)(b + 374 SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK)); 375 if (size < SLOB_BREAK1) 376 slob_list = &free_slob_small; 377 else if (size < SLOB_BREAK2) 378 slob_list = &free_slob_medium; 379 else 380 slob_list = &free_slob_large; 381 set_slob_page_free(sp, slob_list); 382 goto out; 383 } 384 385 /* 386 * Otherwise the page is already partially free, so find reinsertion 387 * point. 388 */ 389 sp->units += units; 390 391 if (b < (slob_t *)sp->freelist) { 392 if (b + units == sp->freelist) { 393 units += slob_units(sp->freelist); 394 sp->freelist = slob_next(sp->freelist); 395 } 396 set_slob(b, units, sp->freelist); 397 sp->freelist = b; 398 } else { 399 prev = sp->freelist; 400 next = slob_next(prev); 401 while (b > next) { 402 prev = next; 403 next = slob_next(prev); 404 } 405 406 if (!slob_last(prev) && b + units == next) { 407 units += slob_units(next); 408 set_slob(b, units, slob_next(next)); 409 } else 410 set_slob(b, units, next); 411 412 if (prev + slob_units(prev) == b) { 413 units = slob_units(b) + slob_units(prev); 414 set_slob(prev, units, slob_next(b)); 415 } else 416 set_slob(prev, slob_units(prev), b); 417 } 418out: 419 spin_unlock_irqrestore(&slob_lock, flags); 420} 421 422/* 423 * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend. 424 */ 425 426static __always_inline void * 427__do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller) 428{ 429 unsigned int *m; 430 int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN); 431 void *ret; 432 433 gfp &= gfp_allowed_mask; 434 435 lockdep_trace_alloc(gfp); 436 437 if (size < PAGE_SIZE - align) { 438 if (!size) 439 return ZERO_SIZE_PTR; 440 441 m = slob_alloc(size + align, gfp, align, node); 442 443 if (!m) 444 return NULL; 445 *m = size; 446 ret = (void *)m + align; 447 448 trace_kmalloc_node(caller, ret, 449 size, size + align, gfp, node); 450 } else { 451 unsigned int order = get_order(size); 452 453 if (likely(order)) 454 gfp |= __GFP_COMP; 455 ret = slob_new_pages(gfp, order, node); 456 457 trace_kmalloc_node(caller, ret, 458 size, PAGE_SIZE << order, gfp, node); 459 } 460 461 kmemleak_alloc(ret, size, 1, gfp); 462 return ret; 463} 464 465void *__kmalloc(size_t size, gfp_t gfp) 466{ 467 return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, _RET_IP_); 468} 469EXPORT_SYMBOL(__kmalloc); 470 471void *__kmalloc_track_caller(size_t size, gfp_t gfp, unsigned long caller) 472{ 473 return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, caller); 474} 475 476#ifdef CONFIG_NUMA 477void *__kmalloc_node_track_caller(size_t size, gfp_t gfp, 478 int node, unsigned long caller) 479{ 480 return __do_kmalloc_node(size, gfp, node, caller); 481} 482#endif 483 484void kfree(const void *block) 485{ 486 struct page *sp; 487 488 trace_kfree(_RET_IP_, block); 489 490 if (unlikely(ZERO_OR_NULL_PTR(block))) 491 return; 492 kmemleak_free(block); 493 494 sp = virt_to_page(block); 495 if (PageSlab(sp)) { 496 int align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN); 497 unsigned int *m = (unsigned int *)(block - align); 498 slob_free(m, *m + align); 499 } else 500 __free_pages(sp, compound_order(sp)); 501} 502EXPORT_SYMBOL(kfree); 503 504/* can't use ksize for kmem_cache_alloc memory, only kmalloc */ 505size_t ksize(const void *block) 506{ 507 struct page *sp; 508 int align; 509 unsigned int *m; 510 511 BUG_ON(!block); 512 if (unlikely(block == ZERO_SIZE_PTR)) 513 return 0; 514 515 sp = virt_to_page(block); 516 if (unlikely(!PageSlab(sp))) 517 return PAGE_SIZE << compound_order(sp); 518 519 align = max_t(size_t, ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN); 520 m = (unsigned int *)(block - align); 521 return SLOB_UNITS(*m) * SLOB_UNIT; 522} 523EXPORT_SYMBOL(ksize); 524 525int __kmem_cache_create(struct kmem_cache *c, unsigned long flags) 526{ 527 if (flags & SLAB_DESTROY_BY_RCU) { 528 /* leave room for rcu footer at the end of object */ 529 c->size += sizeof(struct slob_rcu); 530 } 531 c->flags = flags; 532 return 0; 533} 534 535static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node) 536{ 537 void *b; 538 539 flags &= gfp_allowed_mask; 540 541 lockdep_trace_alloc(flags); 542 543 if (c->size < PAGE_SIZE) { 544 b = slob_alloc(c->size, flags, c->align, node); 545 trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size, 546 SLOB_UNITS(c->size) * SLOB_UNIT, 547 flags, node); 548 } else { 549 b = slob_new_pages(flags, get_order(c->size), node); 550 trace_kmem_cache_alloc_node(_RET_IP_, b, c->object_size, 551 PAGE_SIZE << get_order(c->size), 552 flags, node); 553 } 554 555 if (b && c->ctor) 556 c->ctor(b); 557 558 kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags); 559 return b; 560} 561 562void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags) 563{ 564 return slob_alloc_node(cachep, flags, NUMA_NO_NODE); 565} 566EXPORT_SYMBOL(kmem_cache_alloc); 567 568#ifdef CONFIG_NUMA 569void *__kmalloc_node(size_t size, gfp_t gfp, int node) 570{ 571 return __do_kmalloc_node(size, gfp, node, _RET_IP_); 572} 573EXPORT_SYMBOL(__kmalloc_node); 574 575void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t gfp, int node) 576{ 577 return slob_alloc_node(cachep, gfp, node); 578} 579EXPORT_SYMBOL(kmem_cache_alloc_node); 580#endif 581 582static void __kmem_cache_free(void *b, int size) 583{ 584 if (size < PAGE_SIZE) 585 slob_free(b, size); 586 else 587 slob_free_pages(b, get_order(size)); 588} 589 590static void kmem_rcu_free(struct rcu_head *head) 591{ 592 struct slob_rcu *slob_rcu = (struct slob_rcu *)head; 593 void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu)); 594 595 __kmem_cache_free(b, slob_rcu->size); 596} 597 598void kmem_cache_free(struct kmem_cache *c, void *b) 599{ 600 kmemleak_free_recursive(b, c->flags); 601 if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) { 602 struct slob_rcu *slob_rcu; 603 slob_rcu = b + (c->size - sizeof(struct slob_rcu)); 604 slob_rcu->size = c->size; 605 call_rcu(&slob_rcu->head, kmem_rcu_free); 606 } else { 607 __kmem_cache_free(b, c->size); 608 } 609 610 trace_kmem_cache_free(_RET_IP_, b); 611} 612EXPORT_SYMBOL(kmem_cache_free); 613 614int __kmem_cache_shutdown(struct kmem_cache *c) 615{ 616 /* No way to check for remaining objects */ 617 return 0; 618} 619 620int __kmem_cache_shrink(struct kmem_cache *d, bool deactivate) 621{ 622 return 0; 623} 624 625struct kmem_cache kmem_cache_boot = { 626 .name = "kmem_cache", 627 .size = sizeof(struct kmem_cache), 628 .flags = SLAB_PANIC, 629 .align = ARCH_KMALLOC_MINALIGN, 630}; 631 632void __init kmem_cache_init(void) 633{ 634 kmem_cache = &kmem_cache_boot; 635 slab_state = UP; 636} 637 638void __init kmem_cache_init_late(void) 639{ 640 slab_state = FULL; 641} 642