gslice.c revision f2613bf9ed1dcf0bd2e8b131d20b50d146a6316d
1/* GLIB sliced memory - fast concurrent memory chunk allocator 2 * Copyright (C) 2005 Tim Janik 3 * 4 * This library is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU Lesser General Public 6 * License as published by the Free Software Foundation; either 7 * version 2 of the License, or (at your option) any later version. 8 * 9 * This library is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * Lesser General Public License for more details. 13 * 14 * You should have received a copy of the GNU Lesser General Public 15 * License along with this library; if not, write to the 16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330, 17 * Boston, MA 02111-1307, USA. 18 */ 19/* MT safe */ 20#define _XOPEN_SOURCE 600 /* posix_memalign() */ 21#include <stdlib.h> /* posix_memalign() */ 22#include <string.h> 23#include <errno.h> 24#include "config.h" 25#include "gmem.h" /* gslice.h */ 26#include "gthreadinit.h" 27#include "galias.h" 28#include "glib.h" 29#ifdef HAVE_UNISTD_H 30#include <unistd.h> /* sysconf() */ 31#endif 32#ifdef G_OS_WIN32 33#include <windows.h> 34#include <process.h> 35#endif 36 37/* the GSlice allocator is split up into 4 layers, roughly modelled after the slab 38 * allocator and magazine extensions as outlined in: 39 * + [Bonwick94] Jeff Bonwick, The slab allocator: An object-caching kernel 40 * memory allocator. USENIX 1994, http://citeseer.ist.psu.edu/bonwick94slab.html 41 * + [Bonwick01] Bonwick and Jonathan Adams, Magazines and vmem: Extending the 42 * slab allocator to many cpu's and arbitrary resources. 43 * USENIX 2001, http://citeseer.ist.psu.edu/bonwick01magazines.html 44 * the layers are: 45 * - the thread magazines. for each (aligned) chunk size, a magazine (a list) 46 * of recently freed and soon to be allocated chunks is maintained per thread. 47 * this way, most alloc/free requests can be quickly satisfied from per-thread 48 * free lists which only require one g_private_get() call to retrive the 49 * thread handle. 50 * - the magazine cache. allocating and freeing chunks to/from threads only 51 * occours at magazine sizes from a global depot of magazines. the depot 52 * maintaines a 15 second working set of allocated magazines, so full 53 * magazines are not allocated and released too often. 54 * the chunk size dependent magazine sizes automatically adapt (within limits, 55 * see [3]) to lock contention to properly scale performance across a variety 56 * of SMP systems. 57 * - the slab allocator. this allocator allocates slabs (blocks of memory) close 58 * to the system page size or multiples thereof which have to be page aligned. 59 * the blocks are divided into smaller chunks which are used to satisfy 60 * allocations from the upper layers. the space provided by the reminder of 61 * the chunk size division is used for cache colorization (random distribution 62 * of chunk addresses) to improve processor cache utilization. multiple slabs 63 * with the same chunk size are kept in a partially sorted ring to allow O(1) 64 * freeing and allocation of chunks (as long as the allocation of an entirely 65 * new slab can be avoided). 66 * - the page allocator. on most modern systems, posix_memalign(3) or 67 * memalign(3) should be available, so this is used to allocate blocks with 68 * system page size based alignments and sizes or multiples thereof. 69 * if no memalign variant is provided, valloc() is used instead and 70 * block sizes are limited to the system page size (no multiples thereof). 71 * as a fallback, on system without even valloc(), a malloc(3)-based page 72 * allocator with alloc-only behaviour is used. 73 * 74 * NOTES: 75 * [1] some systems memalign(3) implementations may rely on boundary tagging for 76 * the handed out memory chunks. to avoid excessive page-wise fragmentation, 77 * we reserve 2 * sizeof (void*) per block size for the systems memalign(3), 78 * specified in NATIVE_MALLOC_PADDING. 79 * [2] using the slab allocator alone already provides for a fast and efficient 80 * allocator, it doesn't properly scale beyond single-threaded uses though. 81 * also, the slab allocator implements eager free(3)-ing, i.e. does not 82 * provide any form of caching or working set maintenance. so if used alone, 83 * it's vulnerable to trashing for sequences of balanced (alloc, free) pairs 84 * at certain thresholds. 85 * [3] magazine sizes are bound by an implementation specific minimum size and 86 * a chunk size specific maximum to limit magazine storage sizes to roughly 87 * 16KB. 88 * [4] allocating ca. 8 chunks per block/page keeps a good balance between 89 * external and internal fragmentation (<= 12.5%). [Bonwick94] 90 */ 91 92/* --- macros and constants --- */ 93#define LARGEALIGNMENT (256) 94#define P2ALIGNMENT (2 * sizeof (gsize)) /* fits 2 pointers (assumed to be 2 * GLIB_SIZEOF_SIZE_T below) */ 95#define ALIGN(size, base) ((base) * (gsize) (((size) + (base) - 1) / (base))) 96#define NATIVE_MALLOC_PADDING P2ALIGNMENT /* per-page padding left for native malloc(3) see [1] */ 97#define SLAB_INFO_SIZE P2ALIGN (sizeof (SlabInfo) + NATIVE_MALLOC_PADDING) 98#define MAX_MAGAZINE_SIZE (256) /* see [3] and allocator_get_magazine_threshold() for this */ 99#define MIN_MAGAZINE_SIZE (4) 100#define MAX_STAMP_COUNTER (7) /* distributes the load of gettimeofday() */ 101#define MAX_SLAB_CHUNK_SIZE(al) (((al)->max_page_size - SLAB_INFO_SIZE) / 8) /* we want at last 8 chunks per page, see [4] */ 102#define MAX_SLAB_INDEX(al) (SLAB_INDEX (al, MAX_SLAB_CHUNK_SIZE (al)) + 1) 103#define SLAB_INDEX(al, asize) ((asize) / P2ALIGNMENT - 1) /* asize must be P2ALIGNMENT aligned */ 104#define SLAB_CHUNK_SIZE(al, ix) (((ix) + 1) * P2ALIGNMENT) 105#define SLAB_BPAGE_SIZE(al,csz) (8 * (csz) + SLAB_INFO_SIZE) 106 107/* optimized version of ALIGN (size, P2ALIGNMENT) */ 108#if GLIB_SIZEOF_SIZE_T * 2 == 8 /* P2ALIGNMENT */ 109#define P2ALIGN(size) (((size) + 0x7) & ~(gsize) 0x7) 110#elif GLIB_SIZEOF_SIZE_T * 2 == 16 /* P2ALIGNMENT */ 111#define P2ALIGN(size) (((size) + 0xf) & ~(gsize) 0xf) 112#else 113#define P2ALIGN(size) ALIGN (size, P2ALIGNMENT) 114#endif 115 116/* special helpers to avoid gmessage.c dependency */ 117static void mem_error (const char *format, ...) G_GNUC_PRINTF (1,2); 118#define mem_assert(cond) do { if (G_LIKELY (cond)) ; else mem_error ("assertion failed: %s", #cond); } while (0) 119 120/* --- structures --- */ 121typedef struct _ChunkLink ChunkLink; 122typedef struct _SlabInfo SlabInfo; 123typedef struct _CachedMagazine CachedMagazine; 124struct _ChunkLink { 125 ChunkLink *next; 126 ChunkLink *data; 127}; 128struct _SlabInfo { 129 ChunkLink *chunks; 130 guint n_allocated; 131 SlabInfo *next, *prev; 132}; 133typedef struct { 134 ChunkLink *chunks; 135 gsize count; /* approximative chunks list length */ 136} Magazine; 137typedef struct { 138 Magazine *magazine1; /* array of MAX_SLAB_INDEX (allocator) */ 139 Magazine *magazine2; /* array of MAX_SLAB_INDEX (allocator) */ 140} ThreadMemory; 141typedef struct { 142 gboolean always_malloc; 143 gboolean bypass_magazines; 144 gsize working_set_msecs; 145 guint color_increment; 146} SliceConfig; 147typedef struct { 148 /* const after initialization */ 149 gsize min_page_size, max_page_size; 150 SliceConfig config; 151 gsize max_slab_chunk_size_for_magazine_cache; 152 /* magazine cache */ 153 GMutex *magazine_mutex; 154 ChunkLink **magazines; /* array of MAX_SLAB_INDEX (allocator) */ 155 guint *contention_counters; /* array of MAX_SLAB_INDEX (allocator) */ 156 gint mutex_counter; 157 guint stamp_counter; 158 guint last_stamp; 159 /* slab allocator */ 160 GMutex *slab_mutex; 161 SlabInfo **slab_stack; /* array of MAX_SLAB_INDEX (allocator) */ 162 guint color_accu; 163} Allocator; 164 165/* --- prototypes --- */ 166static gpointer slab_allocator_alloc_chunk (gsize chunk_size); 167static void slab_allocator_free_chunk (gsize chunk_size, 168 gpointer mem); 169static void private_thread_memory_cleanup (gpointer data); 170static gpointer allocator_memalign (gsize alignment, 171 gsize memsize); 172static void allocator_memfree (gsize memsize, 173 gpointer mem); 174static inline void magazine_cache_update_stamp (void); 175static inline gsize allocator_get_magazine_threshold (Allocator *allocator, 176 guint ix); 177 178/* --- variables --- */ 179static GPrivate *private_thread_memory = NULL; 180static gsize sys_page_size = 0; 181static Allocator allocator[1] = { { 0, }, }; 182static SliceConfig slice_config = { 183 FALSE, /* always_malloc */ 184 FALSE, /* bypass_magazines */ 185 15 * 1000, /* working_set_msecs */ 186 1, /* color increment, alt: 0x7fffffff */ 187}; 188 189/* --- auxillary funcitons --- */ 190void 191g_slice_set_config (GSliceConfig ckey, 192 gint64 value) 193{ 194 g_return_if_fail (sys_page_size == 0); 195 switch (ckey) 196 { 197 case G_SLICE_CONFIG_ALWAYS_MALLOC: 198 slice_config.always_malloc = value != 0; 199 break; 200 case G_SLICE_CONFIG_BYPASS_MAGAZINES: 201 slice_config.bypass_magazines = value != 0; 202 break; 203 case G_SLICE_CONFIG_WORKING_SET_MSECS: 204 slice_config.working_set_msecs = value; 205 break; 206 case G_SLICE_CONFIG_COLOR_INCREMENT: 207 slice_config.color_increment = value; 208 default: ; 209 } 210} 211 212gint64 213g_slice_get_config (GSliceConfig ckey) 214{ 215 switch (ckey) 216 { 217 case G_SLICE_CONFIG_ALWAYS_MALLOC: 218 return slice_config.always_malloc; 219 case G_SLICE_CONFIG_BYPASS_MAGAZINES: 220 return slice_config.bypass_magazines; 221 case G_SLICE_CONFIG_WORKING_SET_MSECS: 222 return slice_config.working_set_msecs; 223 case G_SLICE_CONFIG_CHUNK_SIZES: 224 return MAX_SLAB_INDEX (allocator); 225 case G_SLICE_CONFIG_COLOR_INCREMENT: 226 return slice_config.color_increment; 227 default: 228 return 0; 229 } 230} 231 232gint64* 233g_slice_get_config_state (GSliceConfig ckey, 234 gint64 address, 235 guint *n_values) 236{ 237 guint i = 0; 238 g_return_val_if_fail (n_values != NULL, NULL); 239 *n_values = 0; 240 switch (ckey) 241 { 242 gint64 array[64]; 243 case G_SLICE_CONFIG_CONTENTION_COUNTER: 244 array[i++] = SLAB_CHUNK_SIZE (allocator, address); 245 array[i++] = allocator->contention_counters[address]; 246 array[i++] = allocator_get_magazine_threshold (allocator, address); 247 *n_values = i; 248 return g_memdup (array, sizeof (array[0]) * *n_values); 249 default: 250 return NULL; 251 } 252} 253 254static void 255g_slice_init_nomessage (void) 256{ 257 /* we may not use g_error() or friends here */ 258 mem_assert (sys_page_size == 0); 259 mem_assert (MIN_MAGAZINE_SIZE >= 4); 260 261#ifdef G_OS_WIN32 262 { 263 SYSTEM_INFO system_info; 264 GetSystemInfo (&system_info); 265 sys_page_size = system_info.dwPageSize; 266 } 267#else 268 sys_page_size = sysconf (_SC_PAGESIZE); /* = sysconf (_SC_PAGE_SIZE); = getpagesize(); */ 269#endif 270 mem_assert (sys_page_size >= 2 * LARGEALIGNMENT); 271 mem_assert ((sys_page_size & (sys_page_size - 1)) == 0); 272 allocator->config = slice_config; 273 allocator->min_page_size = sys_page_size; 274#if HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN 275 /* allow allocation of pages up to 8KB (with 8KB alignment). 276 * this is useful because many medium to large sized structures 277 * fit less than 8 times (see [4]) into 4KB pages. 278 * we allow very small page sizes here, to reduce wastage in 279 * threads if only small allocations are required (this does 280 * bear the risk of incresing allocation times and fragmentation 281 * though). 282 */ 283 allocator->min_page_size = MAX (allocator->min_page_size, 4096); 284 allocator->max_page_size = MAX (allocator->min_page_size, 8192); 285 allocator->min_page_size = MIN (allocator->min_page_size, 128); 286#else 287 /* we can only align to system page size */ 288 allocator->max_page_size = sys_page_size; 289#endif 290 allocator->magazine_mutex = NULL; /* _g_slice_thread_init_nomessage() */ 291 allocator->magazines = g_new0 (ChunkLink*, MAX_SLAB_INDEX (allocator)); 292 allocator->contention_counters = g_new0 (guint, MAX_SLAB_INDEX (allocator)); 293 allocator->mutex_counter = 0; 294 allocator->stamp_counter = MAX_STAMP_COUNTER; /* force initial update */ 295 allocator->last_stamp = 0; 296 allocator->slab_mutex = NULL; /* _g_slice_thread_init_nomessage() */ 297 allocator->slab_stack = g_new0 (SlabInfo*, MAX_SLAB_INDEX (allocator)); 298 allocator->color_accu = 0; 299 magazine_cache_update_stamp(); 300 /* values cached for performance reasons */ 301 allocator->max_slab_chunk_size_for_magazine_cache = MAX_SLAB_CHUNK_SIZE (allocator); 302 if (allocator->config.always_malloc || allocator->config.bypass_magazines) 303 allocator->max_slab_chunk_size_for_magazine_cache = 0; /* non-optimized cases */ 304} 305 306static inline guint 307allocator_categorize (gsize aligned_chunk_size) 308{ 309 /* speed up the likely path */ 310 if (G_LIKELY (aligned_chunk_size && aligned_chunk_size <= allocator->max_slab_chunk_size_for_magazine_cache)) 311 return 1; /* use magazine cache */ 312 313 /* the above will fail (max_slab_chunk_size_for_magazine_cache == 0) if the 314 * allocator is still uninitialized, or if we are not configured to use the 315 * magazine cache. 316 */ 317 if (!sys_page_size) 318 g_slice_init_nomessage (); 319 if (!allocator->config.always_malloc && 320 aligned_chunk_size && 321 aligned_chunk_size <= MAX_SLAB_CHUNK_SIZE (allocator)) 322 { 323 if (allocator->config.bypass_magazines) 324 return 2; /* use slab allocator, see [2] */ 325 return 1; /* use magazine cache */ 326 } 327 return 0; /* use malloc() */ 328} 329 330void 331_g_slice_thread_init_nomessage (void) 332{ 333 /* we may not use g_error() or friends here */ 334 if (!sys_page_size) 335 g_slice_init_nomessage(); 336 private_thread_memory = g_private_new (private_thread_memory_cleanup); 337 allocator->magazine_mutex = g_mutex_new(); 338 allocator->slab_mutex = g_mutex_new(); 339} 340 341static inline void 342g_mutex_lock_a (GMutex *mutex, 343 guint *contention_counter) 344{ 345 gboolean contention = FALSE; 346 if (!g_mutex_trylock (mutex)) 347 { 348 g_mutex_lock (mutex); 349 contention = TRUE; 350 } 351 if (contention) 352 { 353 allocator->mutex_counter++; 354 if (allocator->mutex_counter >= 1) /* quickly adapt to contention */ 355 { 356 allocator->mutex_counter = 0; 357 *contention_counter = MIN (*contention_counter + 1, MAX_MAGAZINE_SIZE); 358 } 359 } 360 else /* !contention */ 361 { 362 allocator->mutex_counter--; 363 if (allocator->mutex_counter < -11) /* moderately recover magazine sizes */ 364 { 365 allocator->mutex_counter = 0; 366 *contention_counter = MAX (*contention_counter, 1) - 1; 367 } 368 } 369} 370 371static inline ThreadMemory* 372thread_memory_from_self (void) 373{ 374 ThreadMemory *tmem = g_private_get (private_thread_memory); 375 if (G_UNLIKELY (!tmem)) 376 { 377 const guint n_magazines = MAX_SLAB_INDEX (allocator); 378 tmem = g_malloc0 (sizeof (ThreadMemory) + sizeof (Magazine) * 2 * n_magazines); 379 tmem->magazine1 = (Magazine*) (tmem + 1); 380 tmem->magazine2 = &tmem->magazine1[n_magazines]; 381 g_private_set (private_thread_memory, tmem); 382 } 383 return tmem; 384} 385 386static inline ChunkLink* 387magazine_chain_pop_head (ChunkLink **magazine_chunks) 388{ 389 /* magazine chains are linked via ChunkLink->next. 390 * each ChunkLink->data of the toplevel chain may point to a subchain, 391 * linked via ChunkLink->next. ChunkLink->data of the subchains just 392 * contains uninitialized junk. 393 */ 394 ChunkLink *chunk = (*magazine_chunks)->data; 395 if (G_UNLIKELY (chunk)) 396 { 397 /* allocating from freed list */ 398 (*magazine_chunks)->data = chunk->next; 399 } 400 else 401 { 402 chunk = *magazine_chunks; 403 *magazine_chunks = chunk->next; 404 } 405 return chunk; 406} 407 408#if 0 /* useful for debugging */ 409static guint 410magazine_count (ChunkLink *head) 411{ 412 guint count = 0; 413 if (!head) 414 return 0; 415 while (head) 416 { 417 ChunkLink *child = head->data; 418 count += 1; 419 for (child = head->data; child; child = child->next) 420 count += 1; 421 head = head->next; 422 } 423 return count; 424} 425#endif 426 427static inline gsize 428allocator_get_magazine_threshold (Allocator *allocator, 429 guint ix) 430{ 431 /* the magazine size calculated here has a lower bound of MIN_MAGAZINE_SIZE, 432 * which is required by the implementation. also, for moderately sized chunks 433 * (say >= 64 bytes), magazine sizes shouldn't be much smaller then the number 434 * of chunks available per page/2 to avoid excessive traffic in the magazine 435 * cache for small to medium sized structures. 436 * the upper bound of the magazine size is effectively provided by 437 * MAX_MAGAZINE_SIZE. for larger chunks, this number is scaled down so that 438 * the content of a single magazine doesn't exceed ca. 16KB. 439 */ 440 gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix); 441 guint threshold = MAX (MIN_MAGAZINE_SIZE, allocator->max_page_size / MAX (5 * chunk_size, 5 * 32)); 442 guint contention_counter = allocator->contention_counters[ix]; 443 if (G_UNLIKELY (contention_counter)) /* single CPU bias */ 444 { 445 /* adapt contention counter thresholds to chunk sizes */ 446 contention_counter = contention_counter * 64 / chunk_size; 447 threshold = MAX (threshold, contention_counter); 448 } 449 return threshold; 450} 451 452/* --- magazine cache --- */ 453static inline void 454magazine_cache_update_stamp (void) 455{ 456 if (allocator->stamp_counter >= MAX_STAMP_COUNTER) 457 { 458 GTimeVal tv; 459 g_get_current_time (&tv); 460 allocator->last_stamp = tv.tv_sec * 1000 + tv.tv_usec / 1000; /* milli seconds */ 461 allocator->stamp_counter = 0; 462 } 463 else 464 allocator->stamp_counter++; 465} 466 467static inline ChunkLink* 468magazine_chain_prepare_fields (ChunkLink *magazine_chunks) 469{ 470 ChunkLink *chunk1; 471 ChunkLink *chunk2; 472 ChunkLink *chunk3; 473 ChunkLink *chunk4; 474 /* checked upon initialization: mem_assert (MIN_MAGAZINE_SIZE >= 4); */ 475 /* ensure a magazine with at least 4 unused data pointers */ 476 chunk1 = magazine_chain_pop_head (&magazine_chunks); 477 chunk2 = magazine_chain_pop_head (&magazine_chunks); 478 chunk3 = magazine_chain_pop_head (&magazine_chunks); 479 chunk4 = magazine_chain_pop_head (&magazine_chunks); 480 chunk4->next = magazine_chunks; 481 chunk3->next = chunk4; 482 chunk2->next = chunk3; 483 chunk1->next = chunk2; 484 return chunk1; 485} 486 487/* access the first 3 fields of a specially prepared magazine chain */ 488#define magazine_chain_prev(mc) ((mc)->data) 489#define magazine_chain_stamp(mc) ((mc)->next->data) 490#define magazine_chain_uint_stamp(mc) GPOINTER_TO_UINT ((mc)->next->data) 491#define magazine_chain_next(mc) ((mc)->next->next->data) 492#define magazine_chain_count(mc) ((mc)->next->next->next->data) 493 494static void 495magazine_cache_trim (Allocator *allocator, 496 guint ix, 497 guint stamp) 498{ 499 /* g_mutex_lock (allocator->mutex); done by caller */ 500 /* trim magazine cache from tail */ 501 ChunkLink *current = magazine_chain_prev (allocator->magazines[ix]); 502 ChunkLink *trash = NULL; 503 while (ABS (stamp - magazine_chain_uint_stamp (current)) >= allocator->config.working_set_msecs) 504 { 505 /* unlink */ 506 ChunkLink *prev = magazine_chain_prev (current); 507 ChunkLink *next = magazine_chain_next (current); 508 magazine_chain_next (prev) = next; 509 magazine_chain_prev (next) = prev; 510 /* clear special fields, put on trash stack */ 511 magazine_chain_next (current) = NULL; 512 magazine_chain_count (current) = NULL; 513 magazine_chain_stamp (current) = NULL; 514 magazine_chain_prev (current) = trash; 515 trash = current; 516 /* fixup list head if required */ 517 if (current == allocator->magazines[ix]) 518 { 519 allocator->magazines[ix] = NULL; 520 break; 521 } 522 current = prev; 523 } 524 g_mutex_unlock (allocator->magazine_mutex); 525 /* free trash */ 526 if (trash) 527 { 528 const gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix); 529 g_mutex_lock (allocator->slab_mutex); 530 while (trash) 531 { 532 current = trash; 533 trash = magazine_chain_prev (current); 534 magazine_chain_prev (current) = NULL; /* clear special field */ 535 while (current) 536 { 537 ChunkLink *chunk = magazine_chain_pop_head (¤t); 538 slab_allocator_free_chunk (chunk_size, chunk); 539 } 540 } 541 g_mutex_unlock (allocator->slab_mutex); 542 } 543} 544 545static void 546magazine_cache_push_magazine (guint ix, 547 ChunkLink *magazine_chunks, 548 gsize count) /* must be >= MIN_MAGAZINE_SIZE */ 549{ 550 ChunkLink *current = magazine_chain_prepare_fields (magazine_chunks); 551 ChunkLink *next, *prev; 552 g_mutex_lock (allocator->magazine_mutex); 553 /* add magazine at head */ 554 next = allocator->magazines[ix]; 555 if (next) 556 prev = magazine_chain_prev (next); 557 else 558 next = prev = current; 559 magazine_chain_next (prev) = current; 560 magazine_chain_prev (next) = current; 561 magazine_chain_prev (current) = prev; 562 magazine_chain_next (current) = next; 563 magazine_chain_count (current) = (gpointer) count; 564 /* stamp magazine */ 565 magazine_cache_update_stamp(); 566 magazine_chain_stamp (current) = GUINT_TO_POINTER (allocator->last_stamp); 567 allocator->magazines[ix] = current; 568 /* free old magazines beyond a certain threshold */ 569 magazine_cache_trim (allocator, ix, allocator->last_stamp); 570 /* g_mutex_unlock (allocator->mutex); was done by magazine_cache_trim() */ 571} 572 573static ChunkLink* 574magazine_cache_pop_magazine (guint ix, 575 gsize *countp) 576{ 577 g_mutex_lock_a (allocator->magazine_mutex, &allocator->contention_counters[ix]); 578 if (!allocator->magazines[ix]) 579 { 580 guint magazine_threshold = allocator_get_magazine_threshold (allocator, ix); 581 gsize i, chunk_size = SLAB_CHUNK_SIZE (allocator, ix); 582 ChunkLink *chunk, *head; 583 g_mutex_unlock (allocator->magazine_mutex); 584 g_mutex_lock (allocator->slab_mutex); 585 head = slab_allocator_alloc_chunk (chunk_size); 586 head->data = NULL; 587 chunk = head; 588 for (i = 1; i < magazine_threshold; i++) 589 { 590 chunk->next = slab_allocator_alloc_chunk (chunk_size); 591 chunk = chunk->next; 592 chunk->data = NULL; 593 } 594 chunk->next = NULL; 595 g_mutex_unlock (allocator->slab_mutex); 596 *countp = i; 597 return head; 598 } 599 else 600 { 601 ChunkLink *current = allocator->magazines[ix]; 602 ChunkLink *prev = magazine_chain_prev (current); 603 ChunkLink *next = magazine_chain_next (current); 604 /* unlink */ 605 magazine_chain_next (prev) = next; 606 magazine_chain_prev (next) = prev; 607 allocator->magazines[ix] = next == current ? NULL : next; 608 g_mutex_unlock (allocator->magazine_mutex); 609 /* clear special fields and hand out */ 610 *countp = (gsize) magazine_chain_count (current); 611 magazine_chain_prev (current) = NULL; 612 magazine_chain_next (current) = NULL; 613 magazine_chain_count (current) = NULL; 614 magazine_chain_stamp (current) = NULL; 615 return current; 616 } 617} 618 619/* --- thread magazines --- */ 620static void 621private_thread_memory_cleanup (gpointer data) 622{ 623 ThreadMemory *tmem = data; 624 const guint n_magazines = MAX_SLAB_INDEX (allocator); 625 guint ix; 626 for (ix = 0; ix < n_magazines; ix++) 627 { 628 Magazine *mags[2]; 629 guint j; 630 mags[0] = &tmem->magazine1[ix]; 631 mags[1] = &tmem->magazine2[ix]; 632 for (j = 0; j < 2; j++) 633 { 634 Magazine *mag = mags[j]; 635 if (mag->count >= MIN_MAGAZINE_SIZE) 636 magazine_cache_push_magazine (ix, mag->chunks, mag->count); 637 else 638 { 639 const gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix); 640 g_mutex_lock (allocator->slab_mutex); 641 while (mag->chunks) 642 { 643 ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks); 644 slab_allocator_free_chunk (chunk_size, chunk); 645 } 646 g_mutex_unlock (allocator->slab_mutex); 647 } 648 } 649 } 650 g_free (tmem); 651} 652 653static void 654thread_memory_magazine1_reload (ThreadMemory *tmem, 655 guint ix) 656{ 657 Magazine *mag = &tmem->magazine1[ix]; 658 mem_assert (mag->chunks == NULL); /* ensure that we may reset mag->count */ 659 mag->count = 0; 660 mag->chunks = magazine_cache_pop_magazine (ix, &mag->count); 661} 662 663static void 664thread_memory_magazine2_unload (ThreadMemory *tmem, 665 guint ix) 666{ 667 Magazine *mag = &tmem->magazine2[ix]; 668 magazine_cache_push_magazine (ix, mag->chunks, mag->count); 669 mag->chunks = NULL; 670 mag->count = 0; 671} 672 673static inline void 674thread_memory_swap_magazines (ThreadMemory *tmem, 675 guint ix) 676{ 677 Magazine xmag = tmem->magazine1[ix]; 678 tmem->magazine1[ix] = tmem->magazine2[ix]; 679 tmem->magazine2[ix] = xmag; 680} 681 682static inline gboolean 683thread_memory_magazine1_is_empty (ThreadMemory *tmem, 684 guint ix) 685{ 686 return tmem->magazine1[ix].chunks == NULL; 687} 688 689static inline gboolean 690thread_memory_magazine2_is_full (ThreadMemory *tmem, 691 guint ix) 692{ 693 return tmem->magazine2[ix].count >= allocator_get_magazine_threshold (allocator, ix); 694} 695 696static inline gpointer 697thread_memory_magazine1_alloc (ThreadMemory *tmem, 698 guint ix) 699{ 700 Magazine *mag = &tmem->magazine1[ix]; 701 ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks); 702 if (G_LIKELY (mag->count > 0)) 703 mag->count--; 704 return chunk; 705} 706 707static inline void 708thread_memory_magazine2_free (ThreadMemory *tmem, 709 guint ix, 710 gpointer mem) 711{ 712 Magazine *mag = &tmem->magazine2[ix]; 713 ChunkLink *chunk = mem; 714 chunk->data = NULL; 715 chunk->next = mag->chunks; 716 mag->chunks = chunk; 717 mag->count++; 718} 719 720/* --- API functions --- */ 721gpointer 722g_slice_alloc (gsize mem_size) 723{ 724 gsize chunk_size; 725 gpointer mem; 726 guint acat; 727 chunk_size = P2ALIGN (mem_size); 728 acat = allocator_categorize (chunk_size); 729 if (G_LIKELY (acat == 1)) /* allocate through magazine layer */ 730 { 731 ThreadMemory *tmem = thread_memory_from_self(); 732 guint ix = SLAB_INDEX (allocator, chunk_size); 733 if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix))) 734 { 735 thread_memory_swap_magazines (tmem, ix); 736 if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix))) 737 thread_memory_magazine1_reload (tmem, ix); 738 } 739 mem = thread_memory_magazine1_alloc (tmem, ix); 740 } 741 else if (acat == 2) /* allocate through slab allocator */ 742 { 743 g_mutex_lock (allocator->slab_mutex); 744 mem = slab_allocator_alloc_chunk (chunk_size); 745 g_mutex_unlock (allocator->slab_mutex); 746 } 747 else /* delegate to system malloc */ 748 mem = g_malloc (mem_size); 749 return mem; 750} 751 752gpointer 753g_slice_alloc0 (gsize mem_size) 754{ 755 gpointer mem = g_slice_alloc (mem_size); 756 if (mem) 757 memset (mem, 0, mem_size); 758 return mem; 759} 760 761void 762g_slice_free1 (gsize mem_size, 763 gpointer mem_block) 764{ 765 gsize chunk_size = P2ALIGN (mem_size); 766 guint acat = allocator_categorize (chunk_size); 767 if (G_UNLIKELY (!mem_block)) 768 /* pass */; 769 else if (G_LIKELY (acat == 1)) /* allocate through magazine layer */ 770 { 771 ThreadMemory *tmem = thread_memory_from_self(); 772 guint ix = SLAB_INDEX (allocator, chunk_size); 773 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix))) 774 { 775 thread_memory_swap_magazines (tmem, ix); 776 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix))) 777 thread_memory_magazine2_unload (tmem, ix); 778 } 779 thread_memory_magazine2_free (tmem, ix, mem_block); 780 } 781 else if (acat == 2) /* allocate through slab allocator */ 782 { 783 g_mutex_lock (allocator->slab_mutex); 784 slab_allocator_free_chunk (chunk_size, mem_block); 785 g_mutex_unlock (allocator->slab_mutex); 786 } 787 else /* delegate to system malloc */ 788 g_free (mem_block); 789} 790 791void 792g_slice_free_chain_with_offset (gsize mem_size, 793 gpointer mem_chain, 794 gsize next_offset) 795{ 796 gpointer slice = mem_chain; 797 /* while the thread magazines and the magazine cache are implemented so that 798 * they can easily be extended to allow for free lists containing more free 799 * lists for the first level nodes, which would allow O(1) freeing in this 800 * function, the benefit of such an extension is questionable, because: 801 * - the magazine size counts will become mere lower bounds which confuses 802 * the code adapting to lock contention; 803 * - freeing a single node to the thread magazines is very fast, so this 804 * O(list_length) operation is multiplied by a fairly small factor; 805 * - memory usage histograms on larger applications seem to indicate that 806 * the amount of released multi node lists is negligible in comparison 807 * to single node releases. 808 * - the major performance bottle neck, namely g_private_get() or 809 * g_mutex_lock()/g_mutex_unlock() has already been moved out of the 810 * inner loop for freeing chained slices. 811 */ 812 gsize chunk_size = P2ALIGN (mem_size); 813 guint acat = allocator_categorize (chunk_size); 814 if (G_LIKELY (acat == 1)) /* allocate through magazine layer */ 815 { 816 ThreadMemory *tmem = thread_memory_from_self(); 817 guint ix = SLAB_INDEX (allocator, chunk_size); 818 while (slice) 819 { 820 guint8 *current = slice; 821 slice = *(gpointer*) (current + next_offset); 822 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix))) 823 { 824 thread_memory_swap_magazines (tmem, ix); 825 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix))) 826 thread_memory_magazine2_unload (tmem, ix); 827 } 828 thread_memory_magazine2_free (tmem, ix, current); 829 } 830 } 831 else if (acat == 2) /* allocate through slab allocator */ 832 { 833 g_mutex_lock (allocator->slab_mutex); 834 while (slice) 835 { 836 guint8 *current = slice; 837 slice = *(gpointer*) (current + next_offset); 838 slab_allocator_free_chunk (chunk_size, current); 839 } 840 g_mutex_unlock (allocator->slab_mutex); 841 } 842 else /* delegate to system malloc */ 843 while (slice) 844 { 845 guint8 *current = slice; 846 slice = *(gpointer*) (current + next_offset); 847 g_free (current); 848 } 849} 850 851/* --- single page allocator --- */ 852static void 853allocator_slab_stack_push (Allocator *allocator, 854 guint ix, 855 SlabInfo *sinfo) 856{ 857 /* insert slab at slab ring head */ 858 if (!allocator->slab_stack[ix]) 859 { 860 sinfo->next = sinfo; 861 sinfo->prev = sinfo; 862 } 863 else 864 { 865 SlabInfo *next = allocator->slab_stack[ix], *prev = next->prev; 866 next->prev = sinfo; 867 prev->next = sinfo; 868 sinfo->next = next; 869 sinfo->prev = prev; 870 } 871 allocator->slab_stack[ix] = sinfo; 872} 873 874static gsize 875allocator_aligned_page_size (Allocator *allocator, 876 gsize n_bytes) 877{ 878 gsize val = 1 << g_bit_storage (n_bytes - 1); 879 val = MAX (val, allocator->min_page_size); 880 return val; 881} 882 883static void 884allocator_add_slab (Allocator *allocator, 885 guint ix, 886 gsize chunk_size) 887{ 888 ChunkLink *chunk; 889 SlabInfo *sinfo; 890 gsize addr, padding, n_chunks, color = 0; 891 gsize page_size = allocator_aligned_page_size (allocator, SLAB_BPAGE_SIZE (allocator, chunk_size)); 892 /* allocate 1 page for the chunks and the slab */ 893 gpointer aligned_memory = allocator_memalign (page_size, page_size - NATIVE_MALLOC_PADDING); 894 guint8 *mem = aligned_memory; 895 guint i; 896 if (!mem) 897 { 898 const gchar *syserr = "unknown error"; 899#if HAVE_STRERROR 900 syserr = strerror (errno); 901#endif 902 mem_error ("failed to allocate %u bytes (alignment: %u): %s\n", 903 (guint) (page_size - NATIVE_MALLOC_PADDING), (guint) page_size, syserr); 904 } 905 /* mask page adress */ 906 addr = ((gsize) mem / page_size) * page_size; 907 /* assert alignment */ 908 mem_assert (aligned_memory == (gpointer) addr); 909 /* basic slab info setup */ 910 sinfo = (SlabInfo*) (mem + page_size - SLAB_INFO_SIZE); 911 sinfo->n_allocated = 0; 912 sinfo->chunks = NULL; 913 /* figure cache colorization */ 914 n_chunks = ((guint8*) sinfo - mem) / chunk_size; 915 padding = ((guint8*) sinfo - mem) - n_chunks * chunk_size; 916 if (padding) 917 { 918 color = (allocator->color_accu * P2ALIGNMENT) % padding; 919 allocator->color_accu += allocator->config.color_increment; 920 } 921 /* add chunks to free list */ 922 chunk = (ChunkLink*) (mem + color); 923 sinfo->chunks = chunk; 924 for (i = 0; i < n_chunks - 1; i++) 925 { 926 chunk->next = (ChunkLink*) ((guint8*) chunk + chunk_size); 927 chunk = chunk->next; 928 } 929 chunk->next = NULL; /* last chunk */ 930 /* add slab to slab ring */ 931 allocator_slab_stack_push (allocator, ix, sinfo); 932} 933 934static gpointer 935slab_allocator_alloc_chunk (gsize chunk_size) 936{ 937 ChunkLink *chunk; 938 guint ix = SLAB_INDEX (allocator, chunk_size); 939 /* ensure non-empty slab */ 940 if (!allocator->slab_stack[ix] || !allocator->slab_stack[ix]->chunks) 941 allocator_add_slab (allocator, ix, chunk_size); 942 /* allocate chunk */ 943 chunk = allocator->slab_stack[ix]->chunks; 944 allocator->slab_stack[ix]->chunks = chunk->next; 945 allocator->slab_stack[ix]->n_allocated++; 946 /* rotate empty slabs */ 947 if (!allocator->slab_stack[ix]->chunks) 948 allocator->slab_stack[ix] = allocator->slab_stack[ix]->next; 949 return chunk; 950} 951 952static void 953slab_allocator_free_chunk (gsize chunk_size, 954 gpointer mem) 955{ 956 ChunkLink *chunk; 957 gboolean was_empty; 958 guint ix = SLAB_INDEX (allocator, chunk_size); 959 gsize page_size = allocator_aligned_page_size (allocator, SLAB_BPAGE_SIZE (allocator, chunk_size)); 960 gsize addr = ((gsize) mem / page_size) * page_size; 961 /* mask page adress */ 962 guint8 *page = (guint8*) addr; 963 SlabInfo *sinfo = (SlabInfo*) (page + page_size - SLAB_INFO_SIZE); 964 /* assert valid chunk count */ 965 mem_assert (sinfo->n_allocated > 0); 966 /* add chunk to free list */ 967 was_empty = sinfo->chunks == NULL; 968 chunk = (ChunkLink*) mem; 969 chunk->next = sinfo->chunks; 970 sinfo->chunks = chunk; 971 sinfo->n_allocated--; 972 /* keep slab ring partially sorted, empty slabs at end */ 973 if (was_empty) 974 { 975 /* unlink slab */ 976 SlabInfo *next = sinfo->next, *prev = sinfo->prev; 977 next->prev = prev; 978 prev->next = next; 979 if (allocator->slab_stack[ix] == sinfo) 980 allocator->slab_stack[ix] = next == sinfo ? NULL : next; 981 /* insert slab at head */ 982 allocator_slab_stack_push (allocator, ix, sinfo); 983 } 984 /* eagerly free complete unused slabs */ 985 if (!sinfo->n_allocated) 986 { 987 /* unlink slab */ 988 SlabInfo *next = sinfo->next, *prev = sinfo->prev; 989 next->prev = prev; 990 prev->next = next; 991 if (allocator->slab_stack[ix] == sinfo) 992 allocator->slab_stack[ix] = next == sinfo ? NULL : next; 993 /* free slab */ 994 allocator_memfree (page_size, page); 995 } 996} 997 998/* --- memalign implementation --- */ 999#ifdef HAVE_MALLOC_H 1000#include <malloc.h> /* memalign() */ 1001#endif 1002 1003/* from config.h: 1004 * define HAVE_POSIX_MEMALIGN 1 // if free(posix_memalign(3)) works, <stdlib.h> 1005 * define HAVE_MEMALIGN 1 // if free(memalign(3)) works, <malloc.h> 1006 * define HAVE_VALLOC 1 // if free(valloc(3)) works, <stdlib.h> or <malloc.h> 1007 * if none is provided, we implement malloc(3)-based alloc-only page alignment 1008 */ 1009 1010#if !(HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC) 1011static GTrashStack *compat_valloc_trash = NULL; 1012#endif 1013 1014static gpointer 1015allocator_memalign (gsize alignment, 1016 gsize memsize) 1017{ 1018 gpointer aligned_memory = NULL; 1019 gint err = ENOMEM; 1020#if HAVE_POSIX_MEMALIGN 1021 err = posix_memalign (&aligned_memory, alignment, memsize); 1022#elif HAVE_MEMALIGN 1023 errno = 0; 1024 aligned_memory = memalign (alignment, memsize); 1025 err = errno; 1026#elif HAVE_VALLOC 1027 errno = 0; 1028 aligned_memory = valloc (memsize); 1029 err = errno; 1030#else 1031 /* simplistic non-freeing page allocator */ 1032 mem_assert (alignment == sys_page_size); 1033 mem_assert (memsize <= sys_page_size); 1034 if (!compat_valloc_trash) 1035 { 1036 const guint n_pages = 16; 1037 guint8 *mem = malloc (n_pages * sys_page_size); 1038 err = errno; 1039 if (mem) 1040 { 1041 gint i = n_pages; 1042 guint8 *amem = (guint8*) ALIGN ((gsize) mem, sys_page_size); 1043 if (amem != mem) 1044 i--; /* mem wasn't page aligned */ 1045 while (--i >= 0) 1046 g_trash_stack_push (&compat_valloc_trash, amem + i * sys_page_size); 1047 } 1048 } 1049 aligned_memory = g_trash_stack_pop (&compat_valloc_trash); 1050#endif 1051 if (!aligned_memory) 1052 errno = err; 1053 return aligned_memory; 1054} 1055 1056static void 1057allocator_memfree (gsize memsize, 1058 gpointer mem) 1059{ 1060#if HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC 1061 free (mem); 1062#else 1063 mem_assert (memsize <= sys_page_size); 1064 g_trash_stack_push (&compat_valloc_trash, mem); 1065#endif 1066} 1067 1068#include <stdio.h> 1069 1070static void 1071mem_error (const char *format, 1072 ...) 1073{ 1074 const char *pname; 1075 va_list args; 1076 /* at least, put out "MEMORY-ERROR", in case we segfault during the rest of the function */ 1077 fputs ("\n***MEMORY-ERROR***: ", stderr); 1078 pname = g_get_prgname(); 1079 fprintf (stderr, "%s[%u]: GSlice: ", pname ? pname : "", getpid()); 1080 va_start (args, format); 1081 vfprintf (stderr, format, args); 1082 va_end (args); 1083 fputs ("\n", stderr); 1084 _exit (1); 1085} 1086 1087#define __G_SLICE_C__ 1088#include "galiasdef.c" 1089