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.
23 #ifdef HAVE_POSIX_MEMALIGN
24 #define _XOPEN_SOURCE 600 /* posix_memalign() */
26 #include <stdlib.h> /* posix_memalign() */
29 #include "gmem.h" /* gslice.h */
30 #include "gthreadinit.h"
34 #include <unistd.h> /* sysconf() */
41 /* the GSlice allocator is split up into 4 layers, roughly modelled after the slab
42 * allocator and magazine extensions as outlined in:
43 * + [Bonwick94] Jeff Bonwick, The slab allocator: An object-caching kernel
44 * memory allocator. USENIX 1994, http://citeseer.ist.psu.edu/bonwick94slab.html
45 * + [Bonwick01] Bonwick and Jonathan Adams, Magazines and vmem: Extending the
46 * slab allocator to many cpu's and arbitrary resources.
47 * USENIX 2001, http://citeseer.ist.psu.edu/bonwick01magazines.html
49 * - the thread magazines. for each (aligned) chunk size, a magazine (a list)
50 * of recently freed and soon to be allocated chunks is maintained per thread.
51 * this way, most alloc/free requests can be quickly satisfied from per-thread
52 * free lists which only require one g_private_get() call to retrive the
54 * - the magazine cache. allocating and freeing chunks to/from threads only
55 * occours at magazine sizes from a global depot of magazines. the depot
56 * maintaines a 15 second working set of allocated magazines, so full
57 * magazines are not allocated and released too often.
58 * the chunk size dependent magazine sizes automatically adapt (within limits,
59 * see [3]) to lock contention to properly scale performance across a variety
61 * - the slab allocator. this allocator allocates slabs (blocks of memory) close
62 * to the system page size or multiples thereof which have to be page aligned.
63 * the blocks are divided into smaller chunks which are used to satisfy
64 * allocations from the upper layers. the space provided by the reminder of
65 * the chunk size division is used for cache colorization (random distribution
66 * of chunk addresses) to improve processor cache utilization. multiple slabs
67 * with the same chunk size are kept in a partially sorted ring to allow O(1)
68 * freeing and allocation of chunks (as long as the allocation of an entirely
69 * new slab can be avoided).
70 * - the page allocator. on most modern systems, posix_memalign(3) or
71 * memalign(3) should be available, so this is used to allocate blocks with
72 * system page size based alignments and sizes or multiples thereof.
73 * if no memalign variant is provided, valloc() is used instead and
74 * block sizes are limited to the system page size (no multiples thereof).
75 * as a fallback, on system without even valloc(), a malloc(3)-based page
76 * allocator with alloc-only behaviour is used.
79 * [1] some systems memalign(3) implementations may rely on boundary tagging for
80 * the handed out memory chunks. to avoid excessive page-wise fragmentation,
81 * we reserve 2 * sizeof (void*) per block size for the systems memalign(3),
82 * specified in NATIVE_MALLOC_PADDING.
83 * [2] using the slab allocator alone already provides for a fast and efficient
84 * allocator, it doesn't properly scale beyond single-threaded uses though.
85 * also, the slab allocator implements eager free(3)-ing, i.e. does not
86 * provide any form of caching or working set maintenance. so if used alone,
87 * it's vulnerable to trashing for sequences of balanced (alloc, free) pairs
88 * at certain thresholds.
89 * [3] magazine sizes are bound by an implementation specific minimum size and
90 * a chunk size specific maximum to limit magazine storage sizes to roughly
92 * [4] allocating ca. 8 chunks per block/page keeps a good balance between
93 * external and internal fragmentation (<= 12.5%). [Bonwick94]
96 /* --- macros and constants --- */
97 #define LARGEALIGNMENT (256)
98 #define P2ALIGNMENT (2 * sizeof (gsize)) /* fits 2 pointers (assumed to be 2 * GLIB_SIZEOF_SIZE_T below) */
99 #define ALIGN(size, base) ((base) * (gsize) (((size) + (base) - 1) / (base)))
100 #define NATIVE_MALLOC_PADDING P2ALIGNMENT /* per-page padding left for native malloc(3) see [1] */
101 #define SLAB_INFO_SIZE P2ALIGN (sizeof (SlabInfo) + NATIVE_MALLOC_PADDING)
102 #define MAX_MAGAZINE_SIZE (256) /* see [3] and allocator_get_magazine_threshold() for this */
103 #define MIN_MAGAZINE_SIZE (4)
104 #define MAX_STAMP_COUNTER (7) /* distributes the load of gettimeofday() */
105 #define MAX_SLAB_CHUNK_SIZE(al) (((al)->max_page_size - SLAB_INFO_SIZE) / 8) /* we want at last 8 chunks per page, see [4] */
106 #define MAX_SLAB_INDEX(al) (SLAB_INDEX (al, MAX_SLAB_CHUNK_SIZE (al)) + 1)
107 #define SLAB_INDEX(al, asize) ((asize) / P2ALIGNMENT - 1) /* asize must be P2ALIGNMENT aligned */
108 #define SLAB_CHUNK_SIZE(al, ix) (((ix) + 1) * P2ALIGNMENT)
109 #define SLAB_BPAGE_SIZE(al,csz) (8 * (csz) + SLAB_INFO_SIZE)
111 /* optimized version of ALIGN (size, P2ALIGNMENT) */
112 #if GLIB_SIZEOF_SIZE_T * 2 == 8 /* P2ALIGNMENT */
113 #define P2ALIGN(size) (((size) + 0x7) & ~(gsize) 0x7)
114 #elif GLIB_SIZEOF_SIZE_T * 2 == 16 /* P2ALIGNMENT */
115 #define P2ALIGN(size) (((size) + 0xf) & ~(gsize) 0xf)
117 #define P2ALIGN(size) ALIGN (size, P2ALIGNMENT)
120 /* special helpers to avoid gmessage.c dependency */
121 static void mem_error (const char *format
, ...) G_GNUC_PRINTF (1,2);
122 #define mem_assert(cond) do { if (G_LIKELY (cond)) ; else mem_error ("assertion failed: %s", #cond); } while (0)
124 /* --- structures --- */
125 typedef struct _ChunkLink ChunkLink
;
126 typedef struct _SlabInfo SlabInfo
;
127 typedef struct _CachedMagazine CachedMagazine
;
135 SlabInfo
*next
, *prev
;
139 gsize count
; /* approximative chunks list length */
142 Magazine
*magazine1
; /* array of MAX_SLAB_INDEX (allocator) */
143 Magazine
*magazine2
; /* array of MAX_SLAB_INDEX (allocator) */
146 gboolean always_malloc
;
147 gboolean bypass_magazines
;
148 gsize working_set_msecs
;
149 guint color_increment
;
152 /* const after initialization */
153 gsize min_page_size
, max_page_size
;
155 gsize max_slab_chunk_size_for_magazine_cache
;
157 GMutex
*magazine_mutex
;
158 ChunkLink
**magazines
; /* array of MAX_SLAB_INDEX (allocator) */
159 guint
*contention_counters
; /* array of MAX_SLAB_INDEX (allocator) */
165 SlabInfo
**slab_stack
; /* array of MAX_SLAB_INDEX (allocator) */
169 /* --- prototypes --- */
170 static gpointer
slab_allocator_alloc_chunk (gsize chunk_size
);
171 static void slab_allocator_free_chunk (gsize chunk_size
,
173 static void private_thread_memory_cleanup (gpointer data
);
174 static gpointer
allocator_memalign (gsize alignment
,
176 static void allocator_memfree (gsize memsize
,
178 static inline void magazine_cache_update_stamp (void);
179 static inline gsize
allocator_get_magazine_threshold (Allocator
*allocator
,
182 /* --- variables --- */
183 static GPrivate
*private_thread_memory
= NULL
;
184 static gsize sys_page_size
= 0;
185 static Allocator allocator
[1] = { { 0, }, };
186 static SliceConfig slice_config
= {
187 FALSE
, /* always_malloc */
188 FALSE
, /* bypass_magazines */
189 15 * 1000, /* working_set_msecs */
190 1, /* color increment, alt: 0x7fffffff */
193 /* --- auxillary funcitons --- */
195 g_slice_set_config (GSliceConfig ckey
,
198 g_return_if_fail (sys_page_size
== 0);
201 case G_SLICE_CONFIG_ALWAYS_MALLOC
:
202 slice_config
.always_malloc
= value
!= 0;
204 case G_SLICE_CONFIG_BYPASS_MAGAZINES
:
205 slice_config
.bypass_magazines
= value
!= 0;
207 case G_SLICE_CONFIG_WORKING_SET_MSECS
:
208 slice_config
.working_set_msecs
= value
;
210 case G_SLICE_CONFIG_COLOR_INCREMENT
:
211 slice_config
.color_increment
= value
;
217 g_slice_get_config (GSliceConfig ckey
)
221 case G_SLICE_CONFIG_ALWAYS_MALLOC
:
222 return slice_config
.always_malloc
;
223 case G_SLICE_CONFIG_BYPASS_MAGAZINES
:
224 return slice_config
.bypass_magazines
;
225 case G_SLICE_CONFIG_WORKING_SET_MSECS
:
226 return slice_config
.working_set_msecs
;
227 case G_SLICE_CONFIG_CHUNK_SIZES
:
228 return MAX_SLAB_INDEX (allocator
);
229 case G_SLICE_CONFIG_COLOR_INCREMENT
:
230 return slice_config
.color_increment
;
237 g_slice_get_config_state (GSliceConfig ckey
,
242 g_return_val_if_fail (n_values
!= NULL
, NULL
);
247 case G_SLICE_CONFIG_CONTENTION_COUNTER
:
248 array
[i
++] = SLAB_CHUNK_SIZE (allocator
, address
);
249 array
[i
++] = allocator
->contention_counters
[address
];
250 array
[i
++] = allocator_get_magazine_threshold (allocator
, address
);
252 return g_memdup (array
, sizeof (array
[0]) * *n_values
);
259 g_slice_init_nomessage (void)
261 /* we may not use g_error() or friends here */
262 mem_assert (sys_page_size
== 0);
263 mem_assert (MIN_MAGAZINE_SIZE
>= 4);
267 SYSTEM_INFO system_info
;
268 GetSystemInfo (&system_info
);
269 sys_page_size
= system_info
.dwPageSize
;
272 sys_page_size
= sysconf (_SC_PAGESIZE
); /* = sysconf (_SC_PAGE_SIZE); = getpagesize(); */
274 mem_assert (sys_page_size
>= 2 * LARGEALIGNMENT
);
275 mem_assert ((sys_page_size
& (sys_page_size
- 1)) == 0);
276 allocator
->config
= slice_config
;
277 allocator
->min_page_size
= sys_page_size
;
278 #if HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN
279 /* allow allocation of pages up to 8KB (with 8KB alignment).
280 * this is useful because many medium to large sized structures
281 * fit less than 8 times (see [4]) into 4KB pages.
282 * we allow very small page sizes here, to reduce wastage in
283 * threads if only small allocations are required (this does
284 * bear the risk of incresing allocation times and fragmentation
287 allocator
->min_page_size
= MAX (allocator
->min_page_size
, 4096);
288 allocator
->max_page_size
= MAX (allocator
->min_page_size
, 8192);
289 allocator
->min_page_size
= MIN (allocator
->min_page_size
, 128);
291 /* we can only align to system page size */
292 allocator
->max_page_size
= sys_page_size
;
294 allocator
->magazine_mutex
= NULL
; /* _g_slice_thread_init_nomessage() */
295 allocator
->magazines
= g_new0 (ChunkLink
*, MAX_SLAB_INDEX (allocator
));
296 allocator
->contention_counters
= g_new0 (guint
, MAX_SLAB_INDEX (allocator
));
297 allocator
->mutex_counter
= 0;
298 allocator
->stamp_counter
= MAX_STAMP_COUNTER
; /* force initial update */
299 allocator
->last_stamp
= 0;
300 allocator
->slab_mutex
= NULL
; /* _g_slice_thread_init_nomessage() */
301 allocator
->slab_stack
= g_new0 (SlabInfo
*, MAX_SLAB_INDEX (allocator
));
302 allocator
->color_accu
= 0;
303 magazine_cache_update_stamp();
304 /* values cached for performance reasons */
305 allocator
->max_slab_chunk_size_for_magazine_cache
= MAX_SLAB_CHUNK_SIZE (allocator
);
306 if (allocator
->config
.always_malloc
|| allocator
->config
.bypass_magazines
)
307 allocator
->max_slab_chunk_size_for_magazine_cache
= 0; /* non-optimized cases */
311 allocator_categorize (gsize aligned_chunk_size
)
313 /* speed up the likely path */
314 if (G_LIKELY (aligned_chunk_size
&& aligned_chunk_size
<= allocator
->max_slab_chunk_size_for_magazine_cache
))
315 return 1; /* use magazine cache */
317 /* the above will fail (max_slab_chunk_size_for_magazine_cache == 0) if the
318 * allocator is still uninitialized, or if we are not configured to use the
322 g_slice_init_nomessage ();
323 if (!allocator
->config
.always_malloc
&&
324 aligned_chunk_size
&&
325 aligned_chunk_size
<= MAX_SLAB_CHUNK_SIZE (allocator
))
327 if (allocator
->config
.bypass_magazines
)
328 return 2; /* use slab allocator, see [2] */
329 return 1; /* use magazine cache */
331 return 0; /* use malloc() */
335 _g_slice_thread_init_nomessage (void)
337 /* we may not use g_error() or friends here */
339 g_slice_init_nomessage();
340 private_thread_memory
= g_private_new (private_thread_memory_cleanup
);
341 allocator
->magazine_mutex
= g_mutex_new();
342 allocator
->slab_mutex
= g_mutex_new();
346 g_mutex_lock_a (GMutex
*mutex
,
347 guint
*contention_counter
)
349 gboolean contention
= FALSE
;
350 if (!g_mutex_trylock (mutex
))
352 g_mutex_lock (mutex
);
357 allocator
->mutex_counter
++;
358 if (allocator
->mutex_counter
>= 1) /* quickly adapt to contention */
360 allocator
->mutex_counter
= 0;
361 *contention_counter
= MIN (*contention_counter
+ 1, MAX_MAGAZINE_SIZE
);
364 else /* !contention */
366 allocator
->mutex_counter
--;
367 if (allocator
->mutex_counter
< -11) /* moderately recover magazine sizes */
369 allocator
->mutex_counter
= 0;
370 *contention_counter
= MAX (*contention_counter
, 1) - 1;
375 static inline ThreadMemory
*
376 thread_memory_from_self (void)
378 ThreadMemory
*tmem
= g_private_get (private_thread_memory
);
379 if (G_UNLIKELY (!tmem
))
381 const guint n_magazines
= MAX_SLAB_INDEX (allocator
);
382 tmem
= g_malloc0 (sizeof (ThreadMemory
) + sizeof (Magazine
) * 2 * n_magazines
);
383 tmem
->magazine1
= (Magazine
*) (tmem
+ 1);
384 tmem
->magazine2
= &tmem
->magazine1
[n_magazines
];
385 g_private_set (private_thread_memory
, tmem
);
390 static inline ChunkLink
*
391 magazine_chain_pop_head (ChunkLink
**magazine_chunks
)
393 /* magazine chains are linked via ChunkLink->next.
394 * each ChunkLink->data of the toplevel chain may point to a subchain,
395 * linked via ChunkLink->next. ChunkLink->data of the subchains just
396 * contains uninitialized junk.
398 ChunkLink
*chunk
= (*magazine_chunks
)->data
;
399 if (G_UNLIKELY (chunk
))
401 /* allocating from freed list */
402 (*magazine_chunks
)->data
= chunk
->next
;
406 chunk
= *magazine_chunks
;
407 *magazine_chunks
= chunk
->next
;
412 #if 0 /* useful for debugging */
414 magazine_count (ChunkLink
*head
)
421 ChunkLink
*child
= head
->data
;
423 for (child
= head
->data
; child
; child
= child
->next
)
432 allocator_get_magazine_threshold (Allocator
*allocator
,
435 /* the magazine size calculated here has a lower bound of MIN_MAGAZINE_SIZE,
436 * which is required by the implementation. also, for moderately sized chunks
437 * (say >= 64 bytes), magazine sizes shouldn't be much smaller then the number
438 * of chunks available per page/2 to avoid excessive traffic in the magazine
439 * cache for small to medium sized structures.
440 * the upper bound of the magazine size is effectively provided by
441 * MAX_MAGAZINE_SIZE. for larger chunks, this number is scaled down so that
442 * the content of a single magazine doesn't exceed ca. 16KB.
444 gsize chunk_size
= SLAB_CHUNK_SIZE (allocator
, ix
);
445 guint threshold
= MAX (MIN_MAGAZINE_SIZE
, allocator
->max_page_size
/ MAX (5 * chunk_size
, 5 * 32));
446 guint contention_counter
= allocator
->contention_counters
[ix
];
447 if (G_UNLIKELY (contention_counter
)) /* single CPU bias */
449 /* adapt contention counter thresholds to chunk sizes */
450 contention_counter
= contention_counter
* 64 / chunk_size
;
451 threshold
= MAX (threshold
, contention_counter
);
456 /* --- magazine cache --- */
458 magazine_cache_update_stamp (void)
460 if (allocator
->stamp_counter
>= MAX_STAMP_COUNTER
)
463 g_get_current_time (&tv
);
464 allocator
->last_stamp
= tv
.tv_sec
* 1000 + tv
.tv_usec
/ 1000; /* milli seconds */
465 allocator
->stamp_counter
= 0;
468 allocator
->stamp_counter
++;
471 static inline ChunkLink
*
472 magazine_chain_prepare_fields (ChunkLink
*magazine_chunks
)
478 /* checked upon initialization: mem_assert (MIN_MAGAZINE_SIZE >= 4); */
479 /* ensure a magazine with at least 4 unused data pointers */
480 chunk1
= magazine_chain_pop_head (&magazine_chunks
);
481 chunk2
= magazine_chain_pop_head (&magazine_chunks
);
482 chunk3
= magazine_chain_pop_head (&magazine_chunks
);
483 chunk4
= magazine_chain_pop_head (&magazine_chunks
);
484 chunk4
->next
= magazine_chunks
;
485 chunk3
->next
= chunk4
;
486 chunk2
->next
= chunk3
;
487 chunk1
->next
= chunk2
;
491 /* access the first 3 fields of a specially prepared magazine chain */
492 #define magazine_chain_prev(mc) ((mc)->data)
493 #define magazine_chain_stamp(mc) ((mc)->next->data)
494 #define magazine_chain_uint_stamp(mc) GPOINTER_TO_UINT ((mc)->next->data)
495 #define magazine_chain_next(mc) ((mc)->next->next->data)
496 #define magazine_chain_count(mc) ((mc)->next->next->next->data)
499 magazine_cache_trim (Allocator
*allocator
,
503 /* g_mutex_lock (allocator->mutex); done by caller */
504 /* trim magazine cache from tail */
505 ChunkLink
*current
= magazine_chain_prev (allocator
->magazines
[ix
]);
506 ChunkLink
*trash
= NULL
;
507 while (ABS (stamp
- magazine_chain_uint_stamp (current
)) >= allocator
->config
.working_set_msecs
)
510 ChunkLink
*prev
= magazine_chain_prev (current
);
511 ChunkLink
*next
= magazine_chain_next (current
);
512 magazine_chain_next (prev
) = next
;
513 magazine_chain_prev (next
) = prev
;
514 /* clear special fields, put on trash stack */
515 magazine_chain_next (current
) = NULL
;
516 magazine_chain_count (current
) = NULL
;
517 magazine_chain_stamp (current
) = NULL
;
518 magazine_chain_prev (current
) = trash
;
520 /* fixup list head if required */
521 if (current
== allocator
->magazines
[ix
])
523 allocator
->magazines
[ix
] = NULL
;
528 g_mutex_unlock (allocator
->magazine_mutex
);
532 const gsize chunk_size
= SLAB_CHUNK_SIZE (allocator
, ix
);
533 g_mutex_lock (allocator
->slab_mutex
);
537 trash
= magazine_chain_prev (current
);
538 magazine_chain_prev (current
) = NULL
; /* clear special field */
541 ChunkLink
*chunk
= magazine_chain_pop_head (¤t
);
542 slab_allocator_free_chunk (chunk_size
, chunk
);
545 g_mutex_unlock (allocator
->slab_mutex
);
550 magazine_cache_push_magazine (guint ix
,
551 ChunkLink
*magazine_chunks
,
552 gsize count
) /* must be >= MIN_MAGAZINE_SIZE */
554 ChunkLink
*current
= magazine_chain_prepare_fields (magazine_chunks
);
555 ChunkLink
*next
, *prev
;
556 g_mutex_lock (allocator
->magazine_mutex
);
557 /* add magazine at head */
558 next
= allocator
->magazines
[ix
];
560 prev
= magazine_chain_prev (next
);
562 next
= prev
= current
;
563 magazine_chain_next (prev
) = current
;
564 magazine_chain_prev (next
) = current
;
565 magazine_chain_prev (current
) = prev
;
566 magazine_chain_next (current
) = next
;
567 magazine_chain_count (current
) = (gpointer
) count
;
569 magazine_cache_update_stamp();
570 magazine_chain_stamp (current
) = GUINT_TO_POINTER (allocator
->last_stamp
);
571 allocator
->magazines
[ix
] = current
;
572 /* free old magazines beyond a certain threshold */
573 magazine_cache_trim (allocator
, ix
, allocator
->last_stamp
);
574 /* g_mutex_unlock (allocator->mutex); was done by magazine_cache_trim() */
578 magazine_cache_pop_magazine (guint ix
,
581 g_mutex_lock_a (allocator
->magazine_mutex
, &allocator
->contention_counters
[ix
]);
582 if (!allocator
->magazines
[ix
])
584 guint magazine_threshold
= allocator_get_magazine_threshold (allocator
, ix
);
585 gsize i
, chunk_size
= SLAB_CHUNK_SIZE (allocator
, ix
);
586 ChunkLink
*chunk
, *head
;
587 g_mutex_unlock (allocator
->magazine_mutex
);
588 g_mutex_lock (allocator
->slab_mutex
);
589 head
= slab_allocator_alloc_chunk (chunk_size
);
592 for (i
= 1; i
< magazine_threshold
; i
++)
594 chunk
->next
= slab_allocator_alloc_chunk (chunk_size
);
599 g_mutex_unlock (allocator
->slab_mutex
);
605 ChunkLink
*current
= allocator
->magazines
[ix
];
606 ChunkLink
*prev
= magazine_chain_prev (current
);
607 ChunkLink
*next
= magazine_chain_next (current
);
609 magazine_chain_next (prev
) = next
;
610 magazine_chain_prev (next
) = prev
;
611 allocator
->magazines
[ix
] = next
== current
? NULL
: next
;
612 g_mutex_unlock (allocator
->magazine_mutex
);
613 /* clear special fields and hand out */
614 *countp
= (gsize
) magazine_chain_count (current
);
615 magazine_chain_prev (current
) = NULL
;
616 magazine_chain_next (current
) = NULL
;
617 magazine_chain_count (current
) = NULL
;
618 magazine_chain_stamp (current
) = NULL
;
623 /* --- thread magazines --- */
625 private_thread_memory_cleanup (gpointer data
)
627 ThreadMemory
*tmem
= data
;
628 const guint n_magazines
= MAX_SLAB_INDEX (allocator
);
630 for (ix
= 0; ix
< n_magazines
; ix
++)
634 mags
[0] = &tmem
->magazine1
[ix
];
635 mags
[1] = &tmem
->magazine2
[ix
];
636 for (j
= 0; j
< 2; j
++)
638 Magazine
*mag
= mags
[j
];
639 if (mag
->count
>= MIN_MAGAZINE_SIZE
)
640 magazine_cache_push_magazine (ix
, mag
->chunks
, mag
->count
);
643 const gsize chunk_size
= SLAB_CHUNK_SIZE (allocator
, ix
);
644 g_mutex_lock (allocator
->slab_mutex
);
647 ChunkLink
*chunk
= magazine_chain_pop_head (&mag
->chunks
);
648 slab_allocator_free_chunk (chunk_size
, chunk
);
650 g_mutex_unlock (allocator
->slab_mutex
);
658 thread_memory_magazine1_reload (ThreadMemory
*tmem
,
661 Magazine
*mag
= &tmem
->magazine1
[ix
];
662 mem_assert (mag
->chunks
== NULL
); /* ensure that we may reset mag->count */
664 mag
->chunks
= magazine_cache_pop_magazine (ix
, &mag
->count
);
668 thread_memory_magazine2_unload (ThreadMemory
*tmem
,
671 Magazine
*mag
= &tmem
->magazine2
[ix
];
672 magazine_cache_push_magazine (ix
, mag
->chunks
, mag
->count
);
678 thread_memory_swap_magazines (ThreadMemory
*tmem
,
681 Magazine xmag
= tmem
->magazine1
[ix
];
682 tmem
->magazine1
[ix
] = tmem
->magazine2
[ix
];
683 tmem
->magazine2
[ix
] = xmag
;
686 static inline gboolean
687 thread_memory_magazine1_is_empty (ThreadMemory
*tmem
,
690 return tmem
->magazine1
[ix
].chunks
== NULL
;
693 static inline gboolean
694 thread_memory_magazine2_is_full (ThreadMemory
*tmem
,
697 return tmem
->magazine2
[ix
].count
>= allocator_get_magazine_threshold (allocator
, ix
);
700 static inline gpointer
701 thread_memory_magazine1_alloc (ThreadMemory
*tmem
,
704 Magazine
*mag
= &tmem
->magazine1
[ix
];
705 ChunkLink
*chunk
= magazine_chain_pop_head (&mag
->chunks
);
706 if (G_LIKELY (mag
->count
> 0))
712 thread_memory_magazine2_free (ThreadMemory
*tmem
,
716 Magazine
*mag
= &tmem
->magazine2
[ix
];
717 ChunkLink
*chunk
= mem
;
719 chunk
->next
= mag
->chunks
;
724 /* --- API functions --- */
726 g_slice_alloc (gsize mem_size
)
731 chunk_size
= P2ALIGN (mem_size
);
732 acat
= allocator_categorize (chunk_size
);
733 if (G_LIKELY (acat
== 1)) /* allocate through magazine layer */
735 ThreadMemory
*tmem
= thread_memory_from_self();
736 guint ix
= SLAB_INDEX (allocator
, chunk_size
);
737 if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem
, ix
)))
739 thread_memory_swap_magazines (tmem
, ix
);
740 if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem
, ix
)))
741 thread_memory_magazine1_reload (tmem
, ix
);
743 mem
= thread_memory_magazine1_alloc (tmem
, ix
);
745 else if (acat
== 2) /* allocate through slab allocator */
747 g_mutex_lock (allocator
->slab_mutex
);
748 mem
= slab_allocator_alloc_chunk (chunk_size
);
749 g_mutex_unlock (allocator
->slab_mutex
);
751 else /* delegate to system malloc */
752 mem
= g_malloc (mem_size
);
757 g_slice_alloc0 (gsize mem_size
)
759 gpointer mem
= g_slice_alloc (mem_size
);
761 memset (mem
, 0, mem_size
);
766 g_slice_free1 (gsize mem_size
,
769 gsize chunk_size
= P2ALIGN (mem_size
);
770 guint acat
= allocator_categorize (chunk_size
);
771 if (G_UNLIKELY (!mem_block
))
773 else if (G_LIKELY (acat
== 1)) /* allocate through magazine layer */
775 ThreadMemory
*tmem
= thread_memory_from_self();
776 guint ix
= SLAB_INDEX (allocator
, chunk_size
);
777 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem
, ix
)))
779 thread_memory_swap_magazines (tmem
, ix
);
780 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem
, ix
)))
781 thread_memory_magazine2_unload (tmem
, ix
);
783 thread_memory_magazine2_free (tmem
, ix
, mem_block
);
785 else if (acat
== 2) /* allocate through slab allocator */
787 g_mutex_lock (allocator
->slab_mutex
);
788 slab_allocator_free_chunk (chunk_size
, mem_block
);
789 g_mutex_unlock (allocator
->slab_mutex
);
791 else /* delegate to system malloc */
796 g_slice_free_chain_with_offset (gsize mem_size
,
800 gpointer slice
= mem_chain
;
801 /* while the thread magazines and the magazine cache are implemented so that
802 * they can easily be extended to allow for free lists containing more free
803 * lists for the first level nodes, which would allow O(1) freeing in this
804 * function, the benefit of such an extension is questionable, because:
805 * - the magazine size counts will become mere lower bounds which confuses
806 * the code adapting to lock contention;
807 * - freeing a single node to the thread magazines is very fast, so this
808 * O(list_length) operation is multiplied by a fairly small factor;
809 * - memory usage histograms on larger applications seem to indicate that
810 * the amount of released multi node lists is negligible in comparison
811 * to single node releases.
812 * - the major performance bottle neck, namely g_private_get() or
813 * g_mutex_lock()/g_mutex_unlock() has already been moved out of the
814 * inner loop for freeing chained slices.
816 gsize chunk_size
= P2ALIGN (mem_size
);
817 guint acat
= allocator_categorize (chunk_size
);
818 if (G_LIKELY (acat
== 1)) /* allocate through magazine layer */
820 ThreadMemory
*tmem
= thread_memory_from_self();
821 guint ix
= SLAB_INDEX (allocator
, chunk_size
);
824 guint8
*current
= slice
;
825 slice
= *(gpointer
*) (current
+ next_offset
);
826 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem
, ix
)))
828 thread_memory_swap_magazines (tmem
, ix
);
829 if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem
, ix
)))
830 thread_memory_magazine2_unload (tmem
, ix
);
832 thread_memory_magazine2_free (tmem
, ix
, current
);
835 else if (acat
== 2) /* allocate through slab allocator */
837 g_mutex_lock (allocator
->slab_mutex
);
840 guint8
*current
= slice
;
841 slice
= *(gpointer
*) (current
+ next_offset
);
842 slab_allocator_free_chunk (chunk_size
, current
);
844 g_mutex_unlock (allocator
->slab_mutex
);
846 else /* delegate to system malloc */
849 guint8
*current
= slice
;
850 slice
= *(gpointer
*) (current
+ next_offset
);
855 /* --- single page allocator --- */
857 allocator_slab_stack_push (Allocator
*allocator
,
861 /* insert slab at slab ring head */
862 if (!allocator
->slab_stack
[ix
])
869 SlabInfo
*next
= allocator
->slab_stack
[ix
], *prev
= next
->prev
;
875 allocator
->slab_stack
[ix
] = sinfo
;
879 allocator_aligned_page_size (Allocator
*allocator
,
882 gsize val
= 1 << g_bit_storage (n_bytes
- 1);
883 val
= MAX (val
, allocator
->min_page_size
);
888 allocator_add_slab (Allocator
*allocator
,
894 gsize addr
, padding
, n_chunks
, color
= 0;
895 gsize page_size
= allocator_aligned_page_size (allocator
, SLAB_BPAGE_SIZE (allocator
, chunk_size
));
896 /* allocate 1 page for the chunks and the slab */
897 gpointer aligned_memory
= allocator_memalign (page_size
, page_size
- NATIVE_MALLOC_PADDING
);
898 guint8
*mem
= aligned_memory
;
902 const gchar
*syserr
= "unknown error";
904 syserr
= strerror (errno
);
906 mem_error ("failed to allocate %u bytes (alignment: %u): %s\n",
907 (guint
) (page_size
- NATIVE_MALLOC_PADDING
), (guint
) page_size
, syserr
);
909 /* mask page adress */
910 addr
= ((gsize
) mem
/ page_size
) * page_size
;
911 /* assert alignment */
912 mem_assert (aligned_memory
== (gpointer
) addr
);
913 /* basic slab info setup */
914 sinfo
= (SlabInfo
*) (mem
+ page_size
- SLAB_INFO_SIZE
);
915 sinfo
->n_allocated
= 0;
916 sinfo
->chunks
= NULL
;
917 /* figure cache colorization */
918 n_chunks
= ((guint8
*) sinfo
- mem
) / chunk_size
;
919 padding
= ((guint8
*) sinfo
- mem
) - n_chunks
* chunk_size
;
922 color
= (allocator
->color_accu
* P2ALIGNMENT
) % padding
;
923 allocator
->color_accu
+= allocator
->config
.color_increment
;
925 /* add chunks to free list */
926 chunk
= (ChunkLink
*) (mem
+ color
);
927 sinfo
->chunks
= chunk
;
928 for (i
= 0; i
< n_chunks
- 1; i
++)
930 chunk
->next
= (ChunkLink
*) ((guint8
*) chunk
+ chunk_size
);
933 chunk
->next
= NULL
; /* last chunk */
934 /* add slab to slab ring */
935 allocator_slab_stack_push (allocator
, ix
, sinfo
);
939 slab_allocator_alloc_chunk (gsize chunk_size
)
942 guint ix
= SLAB_INDEX (allocator
, chunk_size
);
943 /* ensure non-empty slab */
944 if (!allocator
->slab_stack
[ix
] || !allocator
->slab_stack
[ix
]->chunks
)
945 allocator_add_slab (allocator
, ix
, chunk_size
);
947 chunk
= allocator
->slab_stack
[ix
]->chunks
;
948 allocator
->slab_stack
[ix
]->chunks
= chunk
->next
;
949 allocator
->slab_stack
[ix
]->n_allocated
++;
950 /* rotate empty slabs */
951 if (!allocator
->slab_stack
[ix
]->chunks
)
952 allocator
->slab_stack
[ix
] = allocator
->slab_stack
[ix
]->next
;
957 slab_allocator_free_chunk (gsize chunk_size
,
962 guint ix
= SLAB_INDEX (allocator
, chunk_size
);
963 gsize page_size
= allocator_aligned_page_size (allocator
, SLAB_BPAGE_SIZE (allocator
, chunk_size
));
964 gsize addr
= ((gsize
) mem
/ page_size
) * page_size
;
965 /* mask page adress */
966 guint8
*page
= (guint8
*) addr
;
967 SlabInfo
*sinfo
= (SlabInfo
*) (page
+ page_size
- SLAB_INFO_SIZE
);
968 /* assert valid chunk count */
969 mem_assert (sinfo
->n_allocated
> 0);
970 /* add chunk to free list */
971 was_empty
= sinfo
->chunks
== NULL
;
972 chunk
= (ChunkLink
*) mem
;
973 chunk
->next
= sinfo
->chunks
;
974 sinfo
->chunks
= chunk
;
975 sinfo
->n_allocated
--;
976 /* keep slab ring partially sorted, empty slabs at end */
980 SlabInfo
*next
= sinfo
->next
, *prev
= sinfo
->prev
;
983 if (allocator
->slab_stack
[ix
] == sinfo
)
984 allocator
->slab_stack
[ix
] = next
== sinfo
? NULL
: next
;
985 /* insert slab at head */
986 allocator_slab_stack_push (allocator
, ix
, sinfo
);
988 /* eagerly free complete unused slabs */
989 if (!sinfo
->n_allocated
)
992 SlabInfo
*next
= sinfo
->next
, *prev
= sinfo
->prev
;
995 if (allocator
->slab_stack
[ix
] == sinfo
)
996 allocator
->slab_stack
[ix
] = next
== sinfo
? NULL
: next
;
998 allocator_memfree (page_size
, page
);
1002 /* --- memalign implementation --- */
1003 #ifdef HAVE_MALLOC_H
1004 #include <malloc.h> /* memalign() */
1008 * define HAVE_POSIX_MEMALIGN 1 // if free(posix_memalign(3)) works, <stdlib.h>
1009 * define HAVE_MEMALIGN 1 // if free(memalign(3)) works, <malloc.h>
1010 * define HAVE_VALLOC 1 // if free(valloc(3)) works, <stdlib.h> or <malloc.h>
1011 * if none is provided, we implement malloc(3)-based alloc-only page alignment
1014 #if !(HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC)
1015 static GTrashStack
*compat_valloc_trash
= NULL
;
1019 allocator_memalign (gsize alignment
,
1022 gpointer aligned_memory
= NULL
;
1024 #if HAVE_POSIX_MEMALIGN
1025 err
= posix_memalign (&aligned_memory
, alignment
, memsize
);
1028 aligned_memory
= memalign (alignment
, memsize
);
1032 aligned_memory
= valloc (memsize
);
1035 /* simplistic non-freeing page allocator */
1036 mem_assert (alignment
== sys_page_size
);
1037 mem_assert (memsize
<= sys_page_size
);
1038 if (!compat_valloc_trash
)
1040 const guint n_pages
= 16;
1041 guint8
*mem
= malloc (n_pages
* sys_page_size
);
1046 guint8
*amem
= (guint8
*) ALIGN ((gsize
) mem
, sys_page_size
);
1048 i
--; /* mem wasn't page aligned */
1050 g_trash_stack_push (&compat_valloc_trash
, amem
+ i
* sys_page_size
);
1053 aligned_memory
= g_trash_stack_pop (&compat_valloc_trash
);
1055 if (!aligned_memory
)
1057 return aligned_memory
;
1061 allocator_memfree (gsize memsize
,
1064 #if HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC
1067 mem_assert (memsize
<= sys_page_size
);
1068 g_trash_stack_push (&compat_valloc_trash
, mem
);
1075 mem_error (const char *format
,
1080 /* at least, put out "MEMORY-ERROR", in case we segfault during the rest of the function */
1081 fputs ("\n***MEMORY-ERROR***: ", stderr
);
1082 pname
= g_get_prgname();
1083 fprintf (stderr
, "%s[%u]: GSlice: ", pname
? pname
: "", getpid());
1084 va_start (args
, format
);
1085 vfprintf (stderr
, format
, args
);
1087 fputs ("\n", stderr
);
1091 #define __G_SLICE_C__
1092 #include "galiasdef.c"