1 /* GLIB sliced memory - fast concurrent memory chunk allocator
2 * Copyright (C) 2005 Tim Janik
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.
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.
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.
22 #include "glibconfig.h"
24 #if defined HAVE_POSIX_MEMALIGN && defined POSIX_MEMALIGN_WITH_COMPLIANT_ALLOCS
25 # define HAVE_COMPLIANT_POSIX_MEMALIGN 1
28 #if defined(HAVE_COMPLIANT_POSIX_MEMALIGN) && !defined(_XOPEN_SOURCE)
29 #define _XOPEN_SOURCE 600 /* posix_memalign() */
31 #include <stdlib.h> /* posix_memalign() */
36 #include <unistd.h> /* sysconf() */
43 #include <stdio.h> /* fputs/fprintf */
48 #include "gmem.h" /* gslice.h */
49 #include "gstrfuncs.h"
51 #include "gtestutils.h"
53 #include "gthreadprivate.h"
54 #include "glib_trace.h"
55 #include "glib-ctor.h"
57 /* the GSlice allocator is split up into 4 layers, roughly modelled after the slab
58 * allocator and magazine extensions as outlined in:
59 * + [Bonwick94] Jeff Bonwick, The slab allocator: An object-caching kernel
60 * memory allocator. USENIX 1994, http://citeseer.ist.psu.edu/bonwick94slab.html
61 * + [Bonwick01] Bonwick and Jonathan Adams, Magazines and vmem: Extending the
62 * slab allocator to many cpu's and arbitrary resources.
63 * USENIX 2001, http://citeseer.ist.psu.edu/bonwick01magazines.html
65 * - the thread magazines. for each (aligned) chunk size, a magazine (a list)
66 * of recently freed and soon to be allocated chunks is maintained per thread.
67 * this way, most alloc/free requests can be quickly satisfied from per-thread
68 * free lists which only require one g_private_get() call to retrive the
70 * - the magazine cache. allocating and freeing chunks to/from threads only
71 * occours at magazine sizes from a global depot of magazines. the depot
72 * maintaines a 15 second working set of allocated magazines, so full
73 * magazines are not allocated and released too often.
74 * the chunk size dependent magazine sizes automatically adapt (within limits,
75 * see [3]) to lock contention to properly scale performance across a variety
77 * - the slab allocator. this allocator allocates slabs (blocks of memory) close
78 * to the system page size or multiples thereof which have to be page aligned.
79 * the blocks are divided into smaller chunks which are used to satisfy
80 * allocations from the upper layers. the space provided by the reminder of
81 * the chunk size division is used for cache colorization (random distribution
82 * of chunk addresses) to improve processor cache utilization. multiple slabs
83 * with the same chunk size are kept in a partially sorted ring to allow O(1)
84 * freeing and allocation of chunks (as long as the allocation of an entirely
85 * new slab can be avoided).
86 * - the page allocator. on most modern systems, posix_memalign(3) or
87 * memalign(3) should be available, so this is used to allocate blocks with
88 * system page size based alignments and sizes or multiples thereof.
89 * if no memalign variant is provided, valloc() is used instead and
90 * block sizes are limited to the system page size (no multiples thereof).
91 * as a fallback, on system without even valloc(), a malloc(3)-based page
92 * allocator with alloc-only behaviour is used.
95 * [1] some systems memalign(3) implementations may rely on boundary tagging for
96 * the handed out memory chunks. to avoid excessive page-wise fragmentation,
97 * we reserve 2 * sizeof (void*) per block size for the systems memalign(3),
98 * specified in NATIVE_MALLOC_PADDING.
99 * [2] using the slab allocator alone already provides for a fast and efficient
100 * allocator, it doesn't properly scale beyond single-threaded uses though.
101 * also, the slab allocator implements eager free(3)-ing, i.e. does not
102 * provide any form of caching or working set maintenance. so if used alone,
103 * it's vulnerable to trashing for sequences of balanced (alloc, free) pairs
104 * at certain thresholds.
105 * [3] magazine sizes are bound by an implementation specific minimum size and
106 * a chunk size specific maximum to limit magazine storage sizes to roughly
108 * [4] allocating ca. 8 chunks per block/page keeps a good balance between
109 * external and internal fragmentation (<= 12.5%). [Bonwick94]
112 /* --- macros and constants --- */
113 #define LARGEALIGNMENT (256)
114 #define P2ALIGNMENT (2 * sizeof (gsize)) /* fits 2 pointers (assumed to be 2 * GLIB_SIZEOF_SIZE_T below) */
115 #define ALIGN(size, base) ((base) * (gsize) (((size) + (base) - 1) / (base)))
116 #define NATIVE_MALLOC_PADDING P2ALIGNMENT /* per-page padding left for native malloc(3) see [1] */
117 #define SLAB_INFO_SIZE P2ALIGN (sizeof (SlabInfo) + NATIVE_MALLOC_PADDING)
118 #define MAX_MAGAZINE_SIZE (256) /* see [3] and allocator_get_magazine_threshold() for this */
119 #define MIN_MAGAZINE_SIZE (4)
120 #define MAX_STAMP_COUNTER (7) /* distributes the load of gettimeofday() */
121 #define MAX_SLAB_CHUNK_SIZE(al) (((al)->max_page_size - SLAB_INFO_SIZE) / 8) /* we want at last 8 chunks per page, see [4] */
122 #define MAX_SLAB_INDEX(al) (SLAB_INDEX (al, MAX_SLAB_CHUNK_SIZE (al)) + 1)
123 #define SLAB_INDEX(al, asize) ((asize) / P2ALIGNMENT - 1) /* asize must be P2ALIGNMENT aligned */
124 #define SLAB_CHUNK_SIZE(al, ix) (((ix) + 1) * P2ALIGNMENT)
125 #define SLAB_BPAGE_SIZE(al,csz) (8 * (csz) + SLAB_INFO_SIZE)
127 /* optimized version of ALIGN (size, P2ALIGNMENT) */
128 #if GLIB_SIZEOF_SIZE_T * 2 == 8 /* P2ALIGNMENT */
129 #define P2ALIGN(size) (((size) + 0x7) & ~(gsize) 0x7)
130 #elif GLIB_SIZEOF_SIZE_T * 2 == 16 /* P2ALIGNMENT */
131 #define P2ALIGN(size) (((size) + 0xf) & ~(gsize) 0xf)
133 #define P2ALIGN(size) ALIGN (size, P2ALIGNMENT)
136 /* special helpers to avoid gmessage.c dependency */
137 static void mem_error (const char *format, ...) G_GNUC_PRINTF (1,2);
138 #define mem_assert(cond) do { if (G_LIKELY (cond)) ; else mem_error ("assertion failed: %s", #cond); } while (0)
140 /* --- structures --- */
141 typedef struct _ChunkLink ChunkLink;
142 typedef struct _SlabInfo SlabInfo;
143 typedef struct _CachedMagazine CachedMagazine;
151 SlabInfo *next, *prev;
155 gsize count; /* approximative chunks list length */
158 Magazine *magazine1; /* array of MAX_SLAB_INDEX (allocator) */
159 Magazine *magazine2; /* array of MAX_SLAB_INDEX (allocator) */
162 gboolean always_malloc;
163 gboolean bypass_magazines;
164 gboolean debug_blocks;
165 gsize working_set_msecs;
166 guint color_increment;
169 /* const after initialization */
170 gsize min_page_size, max_page_size;
172 gsize max_slab_chunk_size_for_magazine_cache;
174 GMutex magazine_mutex;
175 ChunkLink **magazines; /* array of MAX_SLAB_INDEX (allocator) */
176 guint *contention_counters; /* array of MAX_SLAB_INDEX (allocator) */
182 SlabInfo **slab_stack; /* array of MAX_SLAB_INDEX (allocator) */
186 /* --- g-slice prototypes --- */
187 static gpointer slab_allocator_alloc_chunk (gsize chunk_size);
188 static void slab_allocator_free_chunk (gsize chunk_size,
190 static void private_thread_memory_cleanup (gpointer data);
191 static gpointer allocator_memalign (gsize alignment,
193 static void allocator_memfree (gsize memsize,
195 static inline void magazine_cache_update_stamp (void);
196 static inline gsize allocator_get_magazine_threshold (Allocator *allocator,
199 /* --- g-slice memory checker --- */
200 static void smc_notify_alloc (void *pointer,
202 static int smc_notify_free (void *pointer,
205 /* --- variables --- */
206 static GPrivate private_thread_memory;
207 static gsize sys_page_size = 0;
208 static Allocator allocator[1] = { { 0, }, };
209 static SliceConfig slice_config = {
210 FALSE, /* always_malloc */
211 FALSE, /* bypass_magazines */
212 FALSE, /* debug_blocks */
213 15 * 1000, /* working_set_msecs */
214 1, /* color increment, alt: 0x7fffffff */
216 static GMutex smc_tree_mutex = G_MUTEX_INIT; /* mutex for G_SLICE=debug-blocks */
218 /* --- auxiliary funcitons --- */
220 g_slice_set_config (GSliceConfig ckey,
223 g_return_if_fail (sys_page_size == 0);
226 case G_SLICE_CONFIG_ALWAYS_MALLOC:
227 slice_config.always_malloc = value != 0;
229 case G_SLICE_CONFIG_BYPASS_MAGAZINES:
230 slice_config.bypass_magazines = value != 0;
232 case G_SLICE_CONFIG_WORKING_SET_MSECS:
233 slice_config.working_set_msecs = value;
235 case G_SLICE_CONFIG_COLOR_INCREMENT:
236 slice_config.color_increment = value;
242 g_slice_get_config (GSliceConfig ckey)
246 case G_SLICE_CONFIG_ALWAYS_MALLOC:
247 return slice_config.always_malloc;
248 case G_SLICE_CONFIG_BYPASS_MAGAZINES:
249 return slice_config.bypass_magazines;
250 case G_SLICE_CONFIG_WORKING_SET_MSECS:
251 return slice_config.working_set_msecs;
252 case G_SLICE_CONFIG_CHUNK_SIZES:
253 return MAX_SLAB_INDEX (allocator);
254 case G_SLICE_CONFIG_COLOR_INCREMENT:
255 return slice_config.color_increment;
262 g_slice_get_config_state (GSliceConfig ckey,
267 g_return_val_if_fail (n_values != NULL, NULL);
272 case G_SLICE_CONFIG_CONTENTION_COUNTER:
273 array[i++] = SLAB_CHUNK_SIZE (allocator, address);
274 array[i++] = allocator->contention_counters[address];
275 array[i++] = allocator_get_magazine_threshold (allocator, address);
277 return g_memdup (array, sizeof (array[0]) * *n_values);
284 slice_config_init (SliceConfig *config)
286 /* don't use g_malloc/g_message here */
288 const gchar *val = _g_getenv_nomalloc ("G_SLICE", buffer);
289 const GDebugKey keys[] = {
290 { "always-malloc", 1 << 0 },
291 { "debug-blocks", 1 << 1 },
293 gint flags = !val ? 0 : g_parse_debug_string (val, keys, G_N_ELEMENTS (keys));
294 *config = slice_config;
295 if (flags & (1 << 0)) /* always-malloc */
296 config->always_malloc = TRUE;
297 if (flags & (1 << 1)) /* debug-blocks */
298 config->debug_blocks = TRUE;
301 GLIB_CTOR (g_slice_init_nomessage)
303 /* we may not use g_error() or friends here */
304 mem_assert (sys_page_size == 0);
305 mem_assert (MIN_MAGAZINE_SIZE >= 4);
309 SYSTEM_INFO system_info;
310 GetSystemInfo (&system_info);
311 sys_page_size = system_info.dwPageSize;
314 sys_page_size = sysconf (_SC_PAGESIZE); /* = sysconf (_SC_PAGE_SIZE); = getpagesize(); */
316 mem_assert (sys_page_size >= 2 * LARGEALIGNMENT);
317 mem_assert ((sys_page_size & (sys_page_size - 1)) == 0);
318 slice_config_init (&allocator->config);
319 allocator->min_page_size = sys_page_size;
320 #if HAVE_COMPLIANT_POSIX_MEMALIGN || HAVE_MEMALIGN
321 /* allow allocation of pages up to 8KB (with 8KB alignment).
322 * this is useful because many medium to large sized structures
323 * fit less than 8 times (see [4]) into 4KB pages.
324 * we allow very small page sizes here, to reduce wastage in
325 * threads if only small allocations are required (this does
326 * bear the risk of incresing allocation times and fragmentation
329 allocator->min_page_size = MAX (allocator->min_page_size, 4096);
330 allocator->max_page_size = MAX (allocator->min_page_size, 8192);
331 allocator->min_page_size = MIN (allocator->min_page_size, 128);
333 /* we can only align to system page size */
334 allocator->max_page_size = sys_page_size;
336 if (allocator->config.always_malloc)
338 allocator->contention_counters = NULL;
339 allocator->magazines = NULL;
340 allocator->slab_stack = NULL;
344 allocator->contention_counters = g_new0 (guint, MAX_SLAB_INDEX (allocator));
345 allocator->magazines = g_new0 (ChunkLink*, MAX_SLAB_INDEX (allocator));
346 allocator->slab_stack = g_new0 (SlabInfo*, MAX_SLAB_INDEX (allocator));
349 g_mutex_init (&allocator->magazine_mutex);
350 allocator->mutex_counter = 0;
351 allocator->stamp_counter = MAX_STAMP_COUNTER; /* force initial update */
352 allocator->last_stamp = 0;
353 g_mutex_init (&allocator->slab_mutex);
354 allocator->color_accu = 0;
355 magazine_cache_update_stamp();
356 /* values cached for performance reasons */
357 allocator->max_slab_chunk_size_for_magazine_cache = MAX_SLAB_CHUNK_SIZE (allocator);
358 if (allocator->config.always_malloc || allocator->config.bypass_magazines)
359 allocator->max_slab_chunk_size_for_magazine_cache = 0; /* non-optimized cases */
360 /* at this point, g_mem_gc_friendly() should be initialized, this
361 * should have been accomplished by the above g_malloc/g_new calls
363 g_private_init (&private_thread_memory, private_thread_memory_cleanup);
367 allocator_categorize (gsize aligned_chunk_size)
369 GLIB_ENSURE_CTOR (g_slice_init_nomessage);
371 /* speed up the likely path */
372 if (G_LIKELY (aligned_chunk_size && aligned_chunk_size <= allocator->max_slab_chunk_size_for_magazine_cache))
373 return 1; /* use magazine cache */
375 if (!allocator->config.always_malloc &&
376 aligned_chunk_size &&
377 aligned_chunk_size <= MAX_SLAB_CHUNK_SIZE (allocator))
379 if (allocator->config.bypass_magazines)
380 return 2; /* use slab allocator, see [2] */
381 return 1; /* use magazine cache */
383 return 0; /* use malloc() */
387 g_mutex_lock_a (GMutex *mutex,
388 guint *contention_counter)
390 gboolean contention = FALSE;
391 if (!g_mutex_trylock (mutex))
393 g_mutex_lock (mutex);
398 allocator->mutex_counter++;
399 if (allocator->mutex_counter >= 1) /* quickly adapt to contention */
401 allocator->mutex_counter = 0;
402 *contention_counter = MIN (*contention_counter + 1, MAX_MAGAZINE_SIZE);
405 else /* !contention */
407 allocator->mutex_counter--;
408 if (allocator->mutex_counter < -11) /* moderately recover magazine sizes */
410 allocator->mutex_counter = 0;
411 *contention_counter = MAX (*contention_counter, 1) - 1;
416 static inline ThreadMemory*
417 thread_memory_from_self (void)
419 ThreadMemory *tmem = g_private_get (&private_thread_memory);
420 if (G_UNLIKELY (!tmem))
422 const guint n_magazines = MAX_SLAB_INDEX (allocator);
423 tmem = g_malloc0 (sizeof (ThreadMemory) + sizeof (Magazine) * 2 * n_magazines);
424 tmem->magazine1 = (Magazine*) (tmem + 1);
425 tmem->magazine2 = &tmem->magazine1[n_magazines];
426 g_private_set (&private_thread_memory, tmem);
431 static inline ChunkLink*
432 magazine_chain_pop_head (ChunkLink **magazine_chunks)
434 /* magazine chains are linked via ChunkLink->next.
435 * each ChunkLink->data of the toplevel chain may point to a subchain,
436 * linked via ChunkLink->next. ChunkLink->data of the subchains just
437 * contains uninitialized junk.
439 ChunkLink *chunk = (*magazine_chunks)->data;
440 if (G_UNLIKELY (chunk))
442 /* allocating from freed list */
443 (*magazine_chunks)->data = chunk->next;
447 chunk = *magazine_chunks;
448 *magazine_chunks = chunk->next;
453 #if 0 /* useful for debugging */
455 magazine_count (ChunkLink *head)
462 ChunkLink *child = head->data;
464 for (child = head->data; child; child = child->next)
473 allocator_get_magazine_threshold (Allocator *allocator,
476 /* the magazine size calculated here has a lower bound of MIN_MAGAZINE_SIZE,
477 * which is required by the implementation. also, for moderately sized chunks
478 * (say >= 64 bytes), magazine sizes shouldn't be much smaller then the number
479 * of chunks available per page/2 to avoid excessive traffic in the magazine
480 * cache for small to medium sized structures.
481 * the upper bound of the magazine size is effectively provided by
482 * MAX_MAGAZINE_SIZE. for larger chunks, this number is scaled down so that
483 * the content of a single magazine doesn't exceed ca. 16KB.
485 gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
486 guint threshold = MAX (MIN_MAGAZINE_SIZE, allocator->max_page_size / MAX (5 * chunk_size, 5 * 32));
487 guint contention_counter = allocator->contention_counters[ix];
488 if (G_UNLIKELY (contention_counter)) /* single CPU bias */
490 /* adapt contention counter thresholds to chunk sizes */
491 contention_counter = contention_counter * 64 / chunk_size;
492 threshold = MAX (threshold, contention_counter);
497 /* --- magazine cache --- */
499 magazine_cache_update_stamp (void)
501 if (allocator->stamp_counter >= MAX_STAMP_COUNTER)
504 g_get_current_time (&tv);
505 allocator->last_stamp = tv.tv_sec * 1000 + tv.tv_usec / 1000; /* milli seconds */
506 allocator->stamp_counter = 0;
509 allocator->stamp_counter++;
512 static inline ChunkLink*
513 magazine_chain_prepare_fields (ChunkLink *magazine_chunks)
519 /* checked upon initialization: mem_assert (MIN_MAGAZINE_SIZE >= 4); */
520 /* ensure a magazine with at least 4 unused data pointers */
521 chunk1 = magazine_chain_pop_head (&magazine_chunks);
522 chunk2 = magazine_chain_pop_head (&magazine_chunks);
523 chunk3 = magazine_chain_pop_head (&magazine_chunks);
524 chunk4 = magazine_chain_pop_head (&magazine_chunks);
525 chunk4->next = magazine_chunks;
526 chunk3->next = chunk4;
527 chunk2->next = chunk3;
528 chunk1->next = chunk2;
532 /* access the first 3 fields of a specially prepared magazine chain */
533 #define magazine_chain_prev(mc) ((mc)->data)
534 #define magazine_chain_stamp(mc) ((mc)->next->data)
535 #define magazine_chain_uint_stamp(mc) GPOINTER_TO_UINT ((mc)->next->data)
536 #define magazine_chain_next(mc) ((mc)->next->next->data)
537 #define magazine_chain_count(mc) ((mc)->next->next->next->data)
540 magazine_cache_trim (Allocator *allocator,
544 /* g_mutex_lock (allocator->mutex); done by caller */
545 /* trim magazine cache from tail */
546 ChunkLink *current = magazine_chain_prev (allocator->magazines[ix]);
547 ChunkLink *trash = NULL;
548 while (ABS (stamp - magazine_chain_uint_stamp (current)) >= allocator->config.working_set_msecs)
551 ChunkLink *prev = magazine_chain_prev (current);
552 ChunkLink *next = magazine_chain_next (current);
553 magazine_chain_next (prev) = next;
554 magazine_chain_prev (next) = prev;
555 /* clear special fields, put on trash stack */
556 magazine_chain_next (current) = NULL;
557 magazine_chain_count (current) = NULL;
558 magazine_chain_stamp (current) = NULL;
559 magazine_chain_prev (current) = trash;
561 /* fixup list head if required */
562 if (current == allocator->magazines[ix])
564 allocator->magazines[ix] = NULL;
569 g_mutex_unlock (&allocator->magazine_mutex);
573 const gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
574 g_mutex_lock (&allocator->slab_mutex);
578 trash = magazine_chain_prev (current);
579 magazine_chain_prev (current) = NULL; /* clear special field */
582 ChunkLink *chunk = magazine_chain_pop_head (¤t);
583 slab_allocator_free_chunk (chunk_size, chunk);
586 g_mutex_unlock (&allocator->slab_mutex);
591 magazine_cache_push_magazine (guint ix,
592 ChunkLink *magazine_chunks,
593 gsize count) /* must be >= MIN_MAGAZINE_SIZE */
595 ChunkLink *current = magazine_chain_prepare_fields (magazine_chunks);
596 ChunkLink *next, *prev;
597 g_mutex_lock (&allocator->magazine_mutex);
598 /* add magazine at head */
599 next = allocator->magazines[ix];
601 prev = magazine_chain_prev (next);
603 next = prev = current;
604 magazine_chain_next (prev) = current;
605 magazine_chain_prev (next) = current;
606 magazine_chain_prev (current) = prev;
607 magazine_chain_next (current) = next;
608 magazine_chain_count (current) = (gpointer) count;
610 magazine_cache_update_stamp();
611 magazine_chain_stamp (current) = GUINT_TO_POINTER (allocator->last_stamp);
612 allocator->magazines[ix] = current;
613 /* free old magazines beyond a certain threshold */
614 magazine_cache_trim (allocator, ix, allocator->last_stamp);
615 /* g_mutex_unlock (allocator->mutex); was done by magazine_cache_trim() */
619 magazine_cache_pop_magazine (guint ix,
622 g_mutex_lock_a (&allocator->magazine_mutex, &allocator->contention_counters[ix]);
623 if (!allocator->magazines[ix])
625 guint magazine_threshold = allocator_get_magazine_threshold (allocator, ix);
626 gsize i, chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
627 ChunkLink *chunk, *head;
628 g_mutex_unlock (&allocator->magazine_mutex);
629 g_mutex_lock (&allocator->slab_mutex);
630 head = slab_allocator_alloc_chunk (chunk_size);
633 for (i = 1; i < magazine_threshold; i++)
635 chunk->next = slab_allocator_alloc_chunk (chunk_size);
640 g_mutex_unlock (&allocator->slab_mutex);
646 ChunkLink *current = allocator->magazines[ix];
647 ChunkLink *prev = magazine_chain_prev (current);
648 ChunkLink *next = magazine_chain_next (current);
650 magazine_chain_next (prev) = next;
651 magazine_chain_prev (next) = prev;
652 allocator->magazines[ix] = next == current ? NULL : next;
653 g_mutex_unlock (&allocator->magazine_mutex);
654 /* clear special fields and hand out */
655 *countp = (gsize) magazine_chain_count (current);
656 magazine_chain_prev (current) = NULL;
657 magazine_chain_next (current) = NULL;
658 magazine_chain_count (current) = NULL;
659 magazine_chain_stamp (current) = NULL;
664 /* --- thread magazines --- */
666 private_thread_memory_cleanup (gpointer data)
668 ThreadMemory *tmem = data;
669 const guint n_magazines = MAX_SLAB_INDEX (allocator);
671 for (ix = 0; ix < n_magazines; ix++)
675 mags[0] = &tmem->magazine1[ix];
676 mags[1] = &tmem->magazine2[ix];
677 for (j = 0; j < 2; j++)
679 Magazine *mag = mags[j];
680 if (mag->count >= MIN_MAGAZINE_SIZE)
681 magazine_cache_push_magazine (ix, mag->chunks, mag->count);
684 const gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
685 g_mutex_lock (&allocator->slab_mutex);
688 ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks);
689 slab_allocator_free_chunk (chunk_size, chunk);
691 g_mutex_unlock (&allocator->slab_mutex);
699 thread_memory_magazine1_reload (ThreadMemory *tmem,
702 Magazine *mag = &tmem->magazine1[ix];
703 mem_assert (mag->chunks == NULL); /* ensure that we may reset mag->count */
705 mag->chunks = magazine_cache_pop_magazine (ix, &mag->count);
709 thread_memory_magazine2_unload (ThreadMemory *tmem,
712 Magazine *mag = &tmem->magazine2[ix];
713 magazine_cache_push_magazine (ix, mag->chunks, mag->count);
719 thread_memory_swap_magazines (ThreadMemory *tmem,
722 Magazine xmag = tmem->magazine1[ix];
723 tmem->magazine1[ix] = tmem->magazine2[ix];
724 tmem->magazine2[ix] = xmag;
727 static inline gboolean
728 thread_memory_magazine1_is_empty (ThreadMemory *tmem,
731 return tmem->magazine1[ix].chunks == NULL;
734 static inline gboolean
735 thread_memory_magazine2_is_full (ThreadMemory *tmem,
738 return tmem->magazine2[ix].count >= allocator_get_magazine_threshold (allocator, ix);
741 static inline gpointer
742 thread_memory_magazine1_alloc (ThreadMemory *tmem,
745 Magazine *mag = &tmem->magazine1[ix];
746 ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks);
747 if (G_LIKELY (mag->count > 0))
753 thread_memory_magazine2_free (ThreadMemory *tmem,
757 Magazine *mag = &tmem->magazine2[ix];
758 ChunkLink *chunk = mem;
760 chunk->next = mag->chunks;
765 /* --- API functions --- */
767 g_slice_alloc (gsize mem_size)
772 chunk_size = P2ALIGN (mem_size);
773 acat = allocator_categorize (chunk_size);
774 if (G_LIKELY (acat == 1)) /* allocate through magazine layer */
776 ThreadMemory *tmem = thread_memory_from_self();
777 guint ix = SLAB_INDEX (allocator, chunk_size);
778 if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix)))
780 thread_memory_swap_magazines (tmem, ix);
781 if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix)))
782 thread_memory_magazine1_reload (tmem, ix);
784 mem = thread_memory_magazine1_alloc (tmem, ix);
786 else if (acat == 2) /* allocate through slab allocator */
788 g_mutex_lock (&allocator->slab_mutex);
789 mem = slab_allocator_alloc_chunk (chunk_size);
790 g_mutex_unlock (&allocator->slab_mutex);
792 else /* delegate to system malloc */
793 mem = g_malloc (mem_size);
794 if (G_UNLIKELY (allocator->config.debug_blocks))
795 smc_notify_alloc (mem, mem_size);
797 TRACE (GLIB_SLICE_ALLOC((void*)mem, mem_size));
803 g_slice_alloc0 (gsize mem_size)
805 gpointer mem = g_slice_alloc (mem_size);
807 memset (mem, 0, mem_size);
812 g_slice_copy (gsize mem_size,
813 gconstpointer mem_block)
815 gpointer mem = g_slice_alloc (mem_size);
817 memcpy (mem, mem_block, mem_size);
822 g_slice_free1 (gsize mem_size,
825 gsize chunk_size = P2ALIGN (mem_size);
826 guint acat = allocator_categorize (chunk_size);
827 if (G_UNLIKELY (!mem_block))
829 if (G_UNLIKELY (allocator->config.debug_blocks) &&
830 !smc_notify_free (mem_block, mem_size))
832 if (G_LIKELY (acat == 1)) /* allocate through magazine layer */
834 ThreadMemory *tmem = thread_memory_from_self();
835 guint ix = SLAB_INDEX (allocator, chunk_size);
836 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
838 thread_memory_swap_magazines (tmem, ix);
839 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
840 thread_memory_magazine2_unload (tmem, ix);
842 if (G_UNLIKELY (g_mem_gc_friendly))
843 memset (mem_block, 0, chunk_size);
844 thread_memory_magazine2_free (tmem, ix, mem_block);
846 else if (acat == 2) /* allocate through slab allocator */
848 if (G_UNLIKELY (g_mem_gc_friendly))
849 memset (mem_block, 0, chunk_size);
850 g_mutex_lock (&allocator->slab_mutex);
851 slab_allocator_free_chunk (chunk_size, mem_block);
852 g_mutex_unlock (&allocator->slab_mutex);
854 else /* delegate to system malloc */
856 if (G_UNLIKELY (g_mem_gc_friendly))
857 memset (mem_block, 0, mem_size);
860 TRACE (GLIB_SLICE_FREE((void*)mem_block, mem_size));
864 g_slice_free_chain_with_offset (gsize mem_size,
868 gpointer slice = mem_chain;
869 /* while the thread magazines and the magazine cache are implemented so that
870 * they can easily be extended to allow for free lists containing more free
871 * lists for the first level nodes, which would allow O(1) freeing in this
872 * function, the benefit of such an extension is questionable, because:
873 * - the magazine size counts will become mere lower bounds which confuses
874 * the code adapting to lock contention;
875 * - freeing a single node to the thread magazines is very fast, so this
876 * O(list_length) operation is multiplied by a fairly small factor;
877 * - memory usage histograms on larger applications seem to indicate that
878 * the amount of released multi node lists is negligible in comparison
879 * to single node releases.
880 * - the major performance bottle neck, namely g_private_get() or
881 * g_mutex_lock()/g_mutex_unlock() has already been moved out of the
882 * inner loop for freeing chained slices.
884 gsize chunk_size = P2ALIGN (mem_size);
885 guint acat = allocator_categorize (chunk_size);
886 if (G_LIKELY (acat == 1)) /* allocate through magazine layer */
888 ThreadMemory *tmem = thread_memory_from_self();
889 guint ix = SLAB_INDEX (allocator, chunk_size);
892 guint8 *current = slice;
893 slice = *(gpointer*) (current + next_offset);
894 if (G_UNLIKELY (allocator->config.debug_blocks) &&
895 !smc_notify_free (current, mem_size))
897 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
899 thread_memory_swap_magazines (tmem, ix);
900 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
901 thread_memory_magazine2_unload (tmem, ix);
903 if (G_UNLIKELY (g_mem_gc_friendly))
904 memset (current, 0, chunk_size);
905 thread_memory_magazine2_free (tmem, ix, current);
908 else if (acat == 2) /* allocate through slab allocator */
910 g_mutex_lock (&allocator->slab_mutex);
913 guint8 *current = slice;
914 slice = *(gpointer*) (current + next_offset);
915 if (G_UNLIKELY (allocator->config.debug_blocks) &&
916 !smc_notify_free (current, mem_size))
918 if (G_UNLIKELY (g_mem_gc_friendly))
919 memset (current, 0, chunk_size);
920 slab_allocator_free_chunk (chunk_size, current);
922 g_mutex_unlock (&allocator->slab_mutex);
924 else /* delegate to system malloc */
927 guint8 *current = slice;
928 slice = *(gpointer*) (current + next_offset);
929 if (G_UNLIKELY (allocator->config.debug_blocks) &&
930 !smc_notify_free (current, mem_size))
932 if (G_UNLIKELY (g_mem_gc_friendly))
933 memset (current, 0, mem_size);
938 /* --- single page allocator --- */
940 allocator_slab_stack_push (Allocator *allocator,
944 /* insert slab at slab ring head */
945 if (!allocator->slab_stack[ix])
952 SlabInfo *next = allocator->slab_stack[ix], *prev = next->prev;
958 allocator->slab_stack[ix] = sinfo;
962 allocator_aligned_page_size (Allocator *allocator,
965 gsize val = 1 << g_bit_storage (n_bytes - 1);
966 val = MAX (val, allocator->min_page_size);
971 allocator_add_slab (Allocator *allocator,
977 gsize addr, padding, n_chunks, color = 0;
978 gsize page_size = allocator_aligned_page_size (allocator, SLAB_BPAGE_SIZE (allocator, chunk_size));
979 /* allocate 1 page for the chunks and the slab */
980 gpointer aligned_memory = allocator_memalign (page_size, page_size - NATIVE_MALLOC_PADDING);
981 guint8 *mem = aligned_memory;
985 const gchar *syserr = "unknown error";
987 syserr = strerror (errno);
989 mem_error ("failed to allocate %u bytes (alignment: %u): %s\n",
990 (guint) (page_size - NATIVE_MALLOC_PADDING), (guint) page_size, syserr);
992 /* mask page address */
993 addr = ((gsize) mem / page_size) * page_size;
994 /* assert alignment */
995 mem_assert (aligned_memory == (gpointer) addr);
996 /* basic slab info setup */
997 sinfo = (SlabInfo*) (mem + page_size - SLAB_INFO_SIZE);
998 sinfo->n_allocated = 0;
999 sinfo->chunks = NULL;
1000 /* figure cache colorization */
1001 n_chunks = ((guint8*) sinfo - mem) / chunk_size;
1002 padding = ((guint8*) sinfo - mem) - n_chunks * chunk_size;
1005 color = (allocator->color_accu * P2ALIGNMENT) % padding;
1006 allocator->color_accu += allocator->config.color_increment;
1008 /* add chunks to free list */
1009 chunk = (ChunkLink*) (mem + color);
1010 sinfo->chunks = chunk;
1011 for (i = 0; i < n_chunks - 1; i++)
1013 chunk->next = (ChunkLink*) ((guint8*) chunk + chunk_size);
1014 chunk = chunk->next;
1016 chunk->next = NULL; /* last chunk */
1017 /* add slab to slab ring */
1018 allocator_slab_stack_push (allocator, ix, sinfo);
1022 slab_allocator_alloc_chunk (gsize chunk_size)
1025 guint ix = SLAB_INDEX (allocator, chunk_size);
1026 /* ensure non-empty slab */
1027 if (!allocator->slab_stack[ix] || !allocator->slab_stack[ix]->chunks)
1028 allocator_add_slab (allocator, ix, chunk_size);
1029 /* allocate chunk */
1030 chunk = allocator->slab_stack[ix]->chunks;
1031 allocator->slab_stack[ix]->chunks = chunk->next;
1032 allocator->slab_stack[ix]->n_allocated++;
1033 /* rotate empty slabs */
1034 if (!allocator->slab_stack[ix]->chunks)
1035 allocator->slab_stack[ix] = allocator->slab_stack[ix]->next;
1040 slab_allocator_free_chunk (gsize chunk_size,
1045 guint ix = SLAB_INDEX (allocator, chunk_size);
1046 gsize page_size = allocator_aligned_page_size (allocator, SLAB_BPAGE_SIZE (allocator, chunk_size));
1047 gsize addr = ((gsize) mem / page_size) * page_size;
1048 /* mask page address */
1049 guint8 *page = (guint8*) addr;
1050 SlabInfo *sinfo = (SlabInfo*) (page + page_size - SLAB_INFO_SIZE);
1051 /* assert valid chunk count */
1052 mem_assert (sinfo->n_allocated > 0);
1053 /* add chunk to free list */
1054 was_empty = sinfo->chunks == NULL;
1055 chunk = (ChunkLink*) mem;
1056 chunk->next = sinfo->chunks;
1057 sinfo->chunks = chunk;
1058 sinfo->n_allocated--;
1059 /* keep slab ring partially sorted, empty slabs at end */
1063 SlabInfo *next = sinfo->next, *prev = sinfo->prev;
1066 if (allocator->slab_stack[ix] == sinfo)
1067 allocator->slab_stack[ix] = next == sinfo ? NULL : next;
1068 /* insert slab at head */
1069 allocator_slab_stack_push (allocator, ix, sinfo);
1071 /* eagerly free complete unused slabs */
1072 if (!sinfo->n_allocated)
1075 SlabInfo *next = sinfo->next, *prev = sinfo->prev;
1078 if (allocator->slab_stack[ix] == sinfo)
1079 allocator->slab_stack[ix] = next == sinfo ? NULL : next;
1081 allocator_memfree (page_size, page);
1085 /* --- memalign implementation --- */
1086 #ifdef HAVE_MALLOC_H
1087 #include <malloc.h> /* memalign() */
1091 * define HAVE_POSIX_MEMALIGN 1 // if free(posix_memalign(3)) works, <stdlib.h>
1092 * define HAVE_COMPLIANT_POSIX_MEMALIGN 1 // if free(posix_memalign(3)) works for sizes != 2^n, <stdlib.h>
1093 * define HAVE_MEMALIGN 1 // if free(memalign(3)) works, <malloc.h>
1094 * define HAVE_VALLOC 1 // if free(valloc(3)) works, <stdlib.h> or <malloc.h>
1095 * if none is provided, we implement malloc(3)-based alloc-only page alignment
1098 #if !(HAVE_COMPLIANT_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC)
1099 static GTrashStack *compat_valloc_trash = NULL;
1103 allocator_memalign (gsize alignment,
1106 gpointer aligned_memory = NULL;
1108 #if HAVE_COMPLIANT_POSIX_MEMALIGN
1109 err = posix_memalign (&aligned_memory, alignment, memsize);
1112 aligned_memory = memalign (alignment, memsize);
1116 aligned_memory = valloc (memsize);
1119 /* simplistic non-freeing page allocator */
1120 mem_assert (alignment == sys_page_size);
1121 mem_assert (memsize <= sys_page_size);
1122 if (!compat_valloc_trash)
1124 const guint n_pages = 16;
1125 guint8 *mem = malloc (n_pages * sys_page_size);
1130 guint8 *amem = (guint8*) ALIGN ((gsize) mem, sys_page_size);
1132 i--; /* mem wasn't page aligned */
1134 g_trash_stack_push (&compat_valloc_trash, amem + i * sys_page_size);
1137 aligned_memory = g_trash_stack_pop (&compat_valloc_trash);
1139 if (!aligned_memory)
1141 return aligned_memory;
1145 allocator_memfree (gsize memsize,
1148 #if HAVE_COMPLIANT_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC
1151 mem_assert (memsize <= sys_page_size);
1152 g_trash_stack_push (&compat_valloc_trash, mem);
1157 mem_error (const char *format,
1162 /* at least, put out "MEMORY-ERROR", in case we segfault during the rest of the function */
1163 fputs ("\n***MEMORY-ERROR***: ", stderr);
1164 pname = g_get_prgname();
1165 fprintf (stderr, "%s[%ld]: GSlice: ", pname ? pname : "", (long)getpid());
1166 va_start (args, format);
1167 vfprintf (stderr, format, args);
1169 fputs ("\n", stderr);
1174 /* --- g-slice memory checker tree --- */
1175 typedef size_t SmcKType; /* key type */
1176 typedef size_t SmcVType; /* value type */
1181 static void smc_tree_insert (SmcKType key,
1183 static gboolean smc_tree_lookup (SmcKType key,
1185 static gboolean smc_tree_remove (SmcKType key);
1188 /* --- g-slice memory checker implementation --- */
1190 smc_notify_alloc (void *pointer,
1193 size_t adress = (size_t) pointer;
1195 smc_tree_insert (adress, size);
1200 smc_notify_ignore (void *pointer)
1202 size_t adress = (size_t) pointer;
1204 smc_tree_remove (adress);
1209 smc_notify_free (void *pointer,
1212 size_t adress = (size_t) pointer;
1217 return 1; /* ignore */
1218 found_one = smc_tree_lookup (adress, &real_size);
1221 fprintf (stderr, "GSlice: MemChecker: attempt to release non-allocated block: %p size=%" G_GSIZE_FORMAT "\n", pointer, size);
1224 if (real_size != size && (real_size || size))
1226 fprintf (stderr, "GSlice: MemChecker: attempt to release block with invalid size: %p size=%" G_GSIZE_FORMAT " invalid-size=%" G_GSIZE_FORMAT "\n", pointer, real_size, size);
1229 if (!smc_tree_remove (adress))
1231 fprintf (stderr, "GSlice: MemChecker: attempt to release non-allocated block: %p size=%" G_GSIZE_FORMAT "\n", pointer, size);
1234 return 1; /* all fine */
1237 /* --- g-slice memory checker tree implementation --- */
1238 #define SMC_TRUNK_COUNT (4093 /* 16381 */) /* prime, to distribute trunk collisions (big, allocated just once) */
1239 #define SMC_BRANCH_COUNT (511) /* prime, to distribute branch collisions */
1240 #define SMC_TRUNK_EXTENT (SMC_BRANCH_COUNT * 2039) /* key adress space per trunk, should distribute uniformly across BRANCH_COUNT */
1241 #define SMC_TRUNK_HASH(k) ((k / SMC_TRUNK_EXTENT) % SMC_TRUNK_COUNT) /* generate new trunk hash per megabyte (roughly) */
1242 #define SMC_BRANCH_HASH(k) (k % SMC_BRANCH_COUNT)
1246 unsigned int n_entries;
1249 static SmcBranch **smc_tree_root = NULL;
1252 smc_tree_abort (int errval)
1254 const char *syserr = "unknown error";
1256 syserr = strerror (errval);
1258 mem_error ("MemChecker: failure in debugging tree: %s", syserr);
1261 static inline SmcEntry*
1262 smc_tree_branch_grow_L (SmcBranch *branch,
1265 unsigned int old_size = branch->n_entries * sizeof (branch->entries[0]);
1266 unsigned int new_size = old_size + sizeof (branch->entries[0]);
1268 mem_assert (index <= branch->n_entries);
1269 branch->entries = (SmcEntry*) realloc (branch->entries, new_size);
1270 if (!branch->entries)
1271 smc_tree_abort (errno);
1272 entry = branch->entries + index;
1273 g_memmove (entry + 1, entry, (branch->n_entries - index) * sizeof (entry[0]));
1274 branch->n_entries += 1;
1278 static inline SmcEntry*
1279 smc_tree_branch_lookup_nearest_L (SmcBranch *branch,
1282 unsigned int n_nodes = branch->n_entries, offs = 0;
1283 SmcEntry *check = branch->entries;
1285 while (offs < n_nodes)
1287 unsigned int i = (offs + n_nodes) >> 1;
1288 check = branch->entries + i;
1289 cmp = key < check->key ? -1 : key != check->key;
1291 return check; /* return exact match */
1294 else /* (cmp > 0) */
1297 /* check points at last mismatch, cmp > 0 indicates greater key */
1298 return cmp > 0 ? check + 1 : check; /* return insertion position for inexact match */
1302 smc_tree_insert (SmcKType key,
1305 unsigned int ix0, ix1;
1308 g_mutex_lock (&smc_tree_mutex);
1309 ix0 = SMC_TRUNK_HASH (key);
1310 ix1 = SMC_BRANCH_HASH (key);
1313 smc_tree_root = calloc (SMC_TRUNK_COUNT, sizeof (smc_tree_root[0]));
1315 smc_tree_abort (errno);
1317 if (!smc_tree_root[ix0])
1319 smc_tree_root[ix0] = calloc (SMC_BRANCH_COUNT, sizeof (smc_tree_root[0][0]));
1320 if (!smc_tree_root[ix0])
1321 smc_tree_abort (errno);
1323 entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
1324 if (!entry || /* need create */
1325 entry >= smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries || /* need append */
1326 entry->key != key) /* need insert */
1327 entry = smc_tree_branch_grow_L (&smc_tree_root[ix0][ix1], entry - smc_tree_root[ix0][ix1].entries);
1329 entry->value = value;
1330 g_mutex_unlock (&smc_tree_mutex);
1334 smc_tree_lookup (SmcKType key,
1337 SmcEntry *entry = NULL;
1338 unsigned int ix0 = SMC_TRUNK_HASH (key), ix1 = SMC_BRANCH_HASH (key);
1339 gboolean found_one = FALSE;
1341 g_mutex_lock (&smc_tree_mutex);
1342 if (smc_tree_root && smc_tree_root[ix0])
1344 entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
1346 entry < smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries &&
1350 *value_p = entry->value;
1353 g_mutex_unlock (&smc_tree_mutex);
1358 smc_tree_remove (SmcKType key)
1360 unsigned int ix0 = SMC_TRUNK_HASH (key), ix1 = SMC_BRANCH_HASH (key);
1361 gboolean found_one = FALSE;
1362 g_mutex_lock (&smc_tree_mutex);
1363 if (smc_tree_root && smc_tree_root[ix0])
1365 SmcEntry *entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
1367 entry < smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries &&
1370 unsigned int i = entry - smc_tree_root[ix0][ix1].entries;
1371 smc_tree_root[ix0][ix1].n_entries -= 1;
1372 g_memmove (entry, entry + 1, (smc_tree_root[ix0][ix1].n_entries - i) * sizeof (entry[0]));
1373 if (!smc_tree_root[ix0][ix1].n_entries)
1375 /* avoid useless pressure on the memory system */
1376 free (smc_tree_root[ix0][ix1].entries);
1377 smc_tree_root[ix0][ix1].entries = NULL;
1382 g_mutex_unlock (&smc_tree_mutex);
1386 #ifdef G_ENABLE_DEBUG
1388 g_slice_debug_tree_statistics (void)
1390 g_mutex_lock (&smc_tree_mutex);
1393 unsigned int i, j, t = 0, o = 0, b = 0, su = 0, ex = 0, en = 4294967295u;
1395 for (i = 0; i < SMC_TRUNK_COUNT; i++)
1396 if (smc_tree_root[i])
1399 for (j = 0; j < SMC_BRANCH_COUNT; j++)
1400 if (smc_tree_root[i][j].n_entries)
1403 su += smc_tree_root[i][j].n_entries;
1404 en = MIN (en, smc_tree_root[i][j].n_entries);
1405 ex = MAX (ex, smc_tree_root[i][j].n_entries);
1407 else if (smc_tree_root[i][j].entries)
1408 o++; /* formerly used, now empty */
1411 tf = MAX (t, 1.0); /* max(1) to be a valid divisor */
1412 bf = MAX (b, 1.0); /* max(1) to be a valid divisor */
1413 fprintf (stderr, "GSlice: MemChecker: %u trunks, %u branches, %u old branches\n", t, b, o);
1414 fprintf (stderr, "GSlice: MemChecker: %f branches per trunk, %.2f%% utilization\n",
1416 100.0 - (SMC_BRANCH_COUNT - b / tf) / (0.01 * SMC_BRANCH_COUNT));
1417 fprintf (stderr, "GSlice: MemChecker: %f entries per branch, %u minimum, %u maximum\n",
1421 fprintf (stderr, "GSlice: MemChecker: root=NULL\n");
1422 g_mutex_unlock (&smc_tree_mutex);
1424 /* sample statistics (beast + GSLice + 24h scripted core & GUI activity):
1425 * PID %CPU %MEM VSZ RSS COMMAND
1426 * 8887 30.3 45.8 456068 414856 beast-0.7.1 empty.bse
1427 * $ cat /proc/8887/statm # total-program-size resident-set-size shared-pages text/code data/stack library dirty-pages
1428 * 114017 103714 2354 344 0 108676 0
1429 * $ cat /proc/8887/status
1440 * (gdb) print g_slice_debug_tree_statistics ()
1441 * GSlice: MemChecker: 422 trunks, 213068 branches, 0 old branches
1442 * GSlice: MemChecker: 504.900474 branches per trunk, 98.81% utilization
1443 * GSlice: MemChecker: 4.965039 entries per branch, 1 minimum, 37 maximum
1446 #endif /* G_ENABLE_DEBUG */