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glib/glib/gslice.c
Philip Withnall 70ee43f1e9 glib: Add SPDX license headers automatically 
Add SPDX license (but not copyright) headers to all files which follow a
certain pattern in their existing non-machine-readable header comment.

This commit was entirely generated using the command:
```
git ls-files glib/*.[ch] | xargs perl -0777 -pi -e 's/\n \*\n \* This library is free software; you can redistribute it and\/or\n \* modify it under the terms of the GNU Lesser General Public/\n \*\n \* SPDX-License-Identifier: LGPL-2.1-or-later\n \*\n \* This library is free software; you can redistribute it and\/or\n \* modify it under the terms of the GNU Lesser General Public/igs'
```

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Helps: #1415
2022-05-18 09:19:02 +01:00

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/* GLIB sliced memory - fast concurrent memory chunk allocator
* Copyright (C) 2005 Tim Janik
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
/* MT safe */
#include "config.h"
#include "glibconfig.h"
#if defined(HAVE_POSIX_MEMALIGN) && !defined(_XOPEN_SOURCE)
#define _XOPEN_SOURCE 600 /* posix_memalign() */
#endif
#include <stdlib.h> /* posix_memalign() */
#include <string.h>
#include <errno.h>
#ifdef G_OS_UNIX
#include <unistd.h> /* sysconf() */
#endif
#ifdef G_OS_WIN32
#include <windows.h>
#include <process.h>
#endif
#include <stdio.h> /* fputs */
#include "gslice.h"
#include "gmain.h"
#include "gmem.h" /* gslice.h */
#include "gstrfuncs.h"
#include "gutils.h"
#include "gtrashstack.h"
#include "gtestutils.h"
#include "gthread.h"
#include "gthreadprivate.h"
#include "glib_trace.h"
#include "gprintf.h"
#include "gvalgrind.h"
/**
* SECTION:memory_slices
* @title: Memory Slices
* @short_description: efficient way to allocate groups of equal-sized
* chunks of memory
*
* Memory slices provide a space-efficient and multi-processing scalable
* way to allocate equal-sized pieces of memory, just like the original
* #GMemChunks (from GLib 2.8), while avoiding their excessive
* memory-waste, scalability and performance problems.
*
* To achieve these goals, the slice allocator uses a sophisticated,
* layered design that has been inspired by Bonwick's slab allocator
* ([Bonwick94](http://citeseer.ist.psu.edu/bonwick94slab.html)
* Jeff Bonwick, The slab allocator: An object-caching kernel
* memory allocator. USENIX 1994, and
* [Bonwick01](http://citeseer.ist.psu.edu/bonwick01magazines.html)
* Bonwick and Jonathan Adams, Magazines and vmem: Extending the
* slab allocator to many cpu's and arbitrary resources. USENIX 2001)
*
* It uses posix_memalign() to optimize allocations of many equally-sized
* chunks, and has per-thread free lists (the so-called magazine layer)
* to quickly satisfy allocation requests of already known structure sizes.
* This is accompanied by extra caching logic to keep freed memory around
* for some time before returning it to the system. Memory that is unused
* due to alignment constraints is used for cache colorization (random
* distribution of chunk addresses) to improve CPU cache utilization. The
* caching layer of the slice allocator adapts itself to high lock contention
* to improve scalability.
*
* The slice allocator can allocate blocks as small as two pointers, and
* unlike malloc(), it does not reserve extra space per block. For large block
* sizes, g_slice_new() and g_slice_alloc() will automatically delegate to the
* system malloc() implementation. For newly written code it is recommended
* to use the new `g_slice` API instead of g_malloc() and
* friends, as long as objects are not resized during their lifetime and the
* object size used at allocation time is still available when freeing.
*
* Here is an example for using the slice allocator:
* |[<!-- language="C" -->
* gchar *mem[10000];
* gint i;
*
* // Allocate 10000 blocks.
* for (i = 0; i < 10000; i++)
* {
* mem[i] = g_slice_alloc (50);
*
* // Fill in the memory with some junk.
* for (j = 0; j < 50; j++)
* mem[i][j] = i * j;
* }
*
* // Now free all of the blocks.
* for (i = 0; i < 10000; i++)
* g_slice_free1 (50, mem[i]);
* ]|
*
* And here is an example for using the using the slice allocator
* with data structures:
* |[<!-- language="C" -->
* GRealArray *array;
*
* // Allocate one block, using the g_slice_new() macro.
* array = g_slice_new (GRealArray);
*
* // We can now use array just like a normal pointer to a structure.
* array->data = NULL;
* array->len = 0;
* array->alloc = 0;
* array->zero_terminated = (zero_terminated ? 1 : 0);
* array->clear = (clear ? 1 : 0);
* array->elt_size = elt_size;
*
* // We can free the block, so it can be reused.
* g_slice_free (GRealArray, array);
* ]|
*/
/* the GSlice allocator is split up into 4 layers, roughly modelled after the slab
* allocator and magazine extensions as outlined in:
* + [Bonwick94] Jeff Bonwick, The slab allocator: An object-caching kernel
* memory allocator. USENIX 1994, http://citeseer.ist.psu.edu/bonwick94slab.html
* + [Bonwick01] Bonwick and Jonathan Adams, Magazines and vmem: Extending the
* slab allocator to many cpu's and arbitrary resources.
* USENIX 2001, http://citeseer.ist.psu.edu/bonwick01magazines.html
* the layers are:
* - the thread magazines. for each (aligned) chunk size, a magazine (a list)
* of recently freed and soon to be allocated chunks is maintained per thread.
* this way, most alloc/free requests can be quickly satisfied from per-thread
* free lists which only require one g_private_get() call to retrieve the
* thread handle.
* - the magazine cache. allocating and freeing chunks to/from threads only
* occurs at magazine sizes from a global depot of magazines. the depot
* maintaines a 15 second working set of allocated magazines, so full
* magazines are not allocated and released too often.
* the chunk size dependent magazine sizes automatically adapt (within limits,
* see [3]) to lock contention to properly scale performance across a variety
* of SMP systems.
* - the slab allocator. this allocator allocates slabs (blocks of memory) close
* to the system page size or multiples thereof which have to be page aligned.
* the blocks are divided into smaller chunks which are used to satisfy
* allocations from the upper layers. the space provided by the reminder of
* the chunk size division is used for cache colorization (random distribution
* of chunk addresses) to improve processor cache utilization. multiple slabs
* with the same chunk size are kept in a partially sorted ring to allow O(1)
* freeing and allocation of chunks (as long as the allocation of an entirely
* new slab can be avoided).
* - the page allocator. on most modern systems, posix_memalign(3) or
* memalign(3) should be available, so this is used to allocate blocks with
* system page size based alignments and sizes or multiples thereof.
* if no memalign variant is provided, valloc() is used instead and
* block sizes are limited to the system page size (no multiples thereof).
* as a fallback, on system without even valloc(), a malloc(3)-based page
* allocator with alloc-only behaviour is used.
*
* NOTES:
* [1] some systems memalign(3) implementations may rely on boundary tagging for
* the handed out memory chunks. to avoid excessive page-wise fragmentation,
* we reserve 2 * sizeof (void*) per block size for the systems memalign(3),
* specified in NATIVE_MALLOC_PADDING.
* [2] using the slab allocator alone already provides for a fast and efficient
* allocator, it doesn't properly scale beyond single-threaded uses though.
* also, the slab allocator implements eager free(3)-ing, i.e. does not
* provide any form of caching or working set maintenance. so if used alone,
* it's vulnerable to trashing for sequences of balanced (alloc, free) pairs
* at certain thresholds.
* [3] magazine sizes are bound by an implementation specific minimum size and
* a chunk size specific maximum to limit magazine storage sizes to roughly
* 16KB.
* [4] allocating ca. 8 chunks per block/page keeps a good balance between
* external and internal fragmentation (<= 12.5%). [Bonwick94]
*/
/* --- macros and constants --- */
#define LARGEALIGNMENT (256)
#define P2ALIGNMENT (2 * sizeof (gsize)) /* fits 2 pointers (assumed to be 2 * GLIB_SIZEOF_SIZE_T below) */
#define ALIGN(size, base) ((base) * (gsize) (((size) + (base) - 1) / (base)))
#define NATIVE_MALLOC_PADDING P2ALIGNMENT /* per-page padding left for native malloc(3) see [1] */
#define SLAB_INFO_SIZE P2ALIGN (sizeof (SlabInfo) + NATIVE_MALLOC_PADDING)
#define MAX_MAGAZINE_SIZE (256) /* see [3] and allocator_get_magazine_threshold() for this */
#define MIN_MAGAZINE_SIZE (4)
#define MAX_STAMP_COUNTER (7) /* distributes the load of gettimeofday() */
#define MAX_SLAB_CHUNK_SIZE(al) (((al)->max_page_size - SLAB_INFO_SIZE) / 8) /* we want at last 8 chunks per page, see [4] */
#define MAX_SLAB_INDEX(al) (SLAB_INDEX (al, MAX_SLAB_CHUNK_SIZE (al)) + 1)
#define SLAB_INDEX(al, asize) ((asize) / P2ALIGNMENT - 1) /* asize must be P2ALIGNMENT aligned */
#define SLAB_CHUNK_SIZE(al, ix) (((ix) + 1) * P2ALIGNMENT)
#define SLAB_BPAGE_SIZE(al,csz) (8 * (csz) + SLAB_INFO_SIZE)
/* optimized version of ALIGN (size, P2ALIGNMENT) */
#if GLIB_SIZEOF_SIZE_T * 2 == 8 /* P2ALIGNMENT */
#define P2ALIGN(size) (((size) + 0x7) & ~(gsize) 0x7)
#elif GLIB_SIZEOF_SIZE_T * 2 == 16 /* P2ALIGNMENT */
#define P2ALIGN(size) (((size) + 0xf) & ~(gsize) 0xf)
#else
#define P2ALIGN(size) ALIGN (size, P2ALIGNMENT)
#endif
/* special helpers to avoid gmessage.c dependency */
static void mem_error (const char *format, ...) G_GNUC_PRINTF (1,2);
#define mem_assert(cond) do { if (G_LIKELY (cond)) ; else mem_error ("assertion failed: %s", #cond); } while (0)
/* --- structures --- */
typedef struct _ChunkLink ChunkLink;
typedef struct _SlabInfo SlabInfo;
typedef struct _CachedMagazine CachedMagazine;
struct _ChunkLink {
ChunkLink *next;
ChunkLink *data;
};
struct _SlabInfo {
ChunkLink *chunks;
guint n_allocated;
SlabInfo *next, *prev;
};
typedef struct {
ChunkLink *chunks;
gsize count; /* approximative chunks list length */
} Magazine;
typedef struct {
Magazine *magazine1; /* array of MAX_SLAB_INDEX (allocator) */
Magazine *magazine2; /* array of MAX_SLAB_INDEX (allocator) */
} ThreadMemory;
typedef struct {
gboolean always_malloc;
gboolean bypass_magazines;
gboolean debug_blocks;
gsize working_set_msecs;
guint color_increment;
} SliceConfig;
typedef struct {
/* const after initialization */
gsize min_page_size, max_page_size;
SliceConfig config;
gsize max_slab_chunk_size_for_magazine_cache;
/* magazine cache */
GMutex magazine_mutex;
ChunkLink **magazines; /* array of MAX_SLAB_INDEX (allocator) */
guint *contention_counters; /* array of MAX_SLAB_INDEX (allocator) */
gint mutex_counter;
guint stamp_counter;
guint last_stamp;
/* slab allocator */
GMutex slab_mutex;
SlabInfo **slab_stack; /* array of MAX_SLAB_INDEX (allocator) */
guint color_accu;
} Allocator;
/* --- g-slice prototypes --- */
static gpointer slab_allocator_alloc_chunk (gsize chunk_size);
static void slab_allocator_free_chunk (gsize chunk_size,
gpointer mem);
static void private_thread_memory_cleanup (gpointer data);
static gpointer allocator_memalign (gsize alignment,
gsize memsize);
static void allocator_memfree (gsize memsize,
gpointer mem);
static inline void magazine_cache_update_stamp (void);
static inline gsize allocator_get_magazine_threshold (Allocator *allocator,
guint ix);
/* --- g-slice memory checker --- */
static void smc_notify_alloc (void *pointer,
size_t size);
static int smc_notify_free (void *pointer,
size_t size);
/* --- variables --- */
static GPrivate private_thread_memory = G_PRIVATE_INIT (private_thread_memory_cleanup);
static gsize sys_page_size = 0;
static Allocator allocator[1] = { { 0, }, };
static SliceConfig slice_config = {
FALSE, /* always_malloc */
FALSE, /* bypass_magazines */
FALSE, /* debug_blocks */
15 * 1000, /* working_set_msecs */
1, /* color increment, alt: 0x7fffffff */
};
static GMutex smc_tree_mutex; /* mutex for G_SLICE=debug-blocks */
/* --- auxiliary functions --- */
void
g_slice_set_config (GSliceConfig ckey,
gint64 value)
{
g_return_if_fail (sys_page_size == 0);
switch (ckey)
{
case G_SLICE_CONFIG_ALWAYS_MALLOC:
slice_config.always_malloc = value != 0;
break;
case G_SLICE_CONFIG_BYPASS_MAGAZINES:
slice_config.bypass_magazines = value != 0;
break;
case G_SLICE_CONFIG_WORKING_SET_MSECS:
slice_config.working_set_msecs = value;
break;
case G_SLICE_CONFIG_COLOR_INCREMENT:
slice_config.color_increment = value;
break;
default: ;
}
}
gint64
g_slice_get_config (GSliceConfig ckey)
{
switch (ckey)
{
case G_SLICE_CONFIG_ALWAYS_MALLOC:
return slice_config.always_malloc;
case G_SLICE_CONFIG_BYPASS_MAGAZINES:
return slice_config.bypass_magazines;
case G_SLICE_CONFIG_WORKING_SET_MSECS:
return slice_config.working_set_msecs;
case G_SLICE_CONFIG_CHUNK_SIZES:
return MAX_SLAB_INDEX (allocator);
case G_SLICE_CONFIG_COLOR_INCREMENT:
return slice_config.color_increment;
default:
return 0;
}
}
gint64*
g_slice_get_config_state (GSliceConfig ckey,
gint64 address,
guint *n_values)
{
guint i = 0;
g_return_val_if_fail (n_values != NULL, NULL);
*n_values = 0;
switch (ckey)
{
gint64 array[64];
case G_SLICE_CONFIG_CONTENTION_COUNTER:
array[i++] = SLAB_CHUNK_SIZE (allocator, address);
array[i++] = allocator->contention_counters[address];
array[i++] = allocator_get_magazine_threshold (allocator, address);
*n_values = i;
return g_memdup2 (array, sizeof (array[0]) * *n_values);
default:
return NULL;
}
}
static void
slice_config_init (SliceConfig *config)
{
const gchar *val;
gchar *val_allocated = NULL;
*config = slice_config;
/* Note that the empty string (`G_SLICE=""`) is treated differently from the
* envvar being unset. In the latter case, we also check whether running under
* valgrind. */
#ifndef G_OS_WIN32
val = g_getenv ("G_SLICE");
#else
/* The win32 implementation of g_getenv() has to do UTF-8 ↔ UTF-16 conversions
* which use the slice allocator, leading to deadlock. Use a simple in-place
* implementation here instead.
*
* Ignore references to other environment variables: only support values which
* are a combination of always-malloc and debug-blocks. */
{
wchar_t wvalue[128]; /* at least big enough for `always-malloc,debug-blocks` */
gsize len;
len = GetEnvironmentVariableW (L"G_SLICE", wvalue, G_N_ELEMENTS (wvalue));
if (len == 0)
{
if (GetLastError () == ERROR_ENVVAR_NOT_FOUND)
val = NULL;
else
val = "";
}
else if (len >= G_N_ELEMENTS (wvalue))
{
/* @wvalue isn’t big enough. Give up. */
g_warning ("Unsupported G_SLICE value");
val = NULL;
}
else
{
/* it’s safe to use g_utf16_to_utf8() here as it only allocates using
* malloc() rather than GSlice */
val = val_allocated = g_utf16_to_utf8 (wvalue, -1, NULL, NULL, NULL);
}
}
#endif /* G_OS_WIN32 */
if (val != NULL)
{
gint flags;
const GDebugKey keys[] = {
{ "always-malloc", 1 << 0 },
{ "debug-blocks", 1 << 1 },
};
flags = g_parse_debug_string (val, keys, G_N_ELEMENTS (keys));
if (flags & (1 << 0))
config->always_malloc = TRUE;
if (flags & (1 << 1))
config->debug_blocks = TRUE;
}
else
{
/* G_SLICE was not specified, so check if valgrind is running and
* disable ourselves if it is.
*
* This way it's possible to force gslice to be enabled under
* valgrind just by setting G_SLICE to the empty string.
*/
#ifdef ENABLE_VALGRIND
if (RUNNING_ON_VALGRIND)
config->always_malloc = TRUE;
#endif
}
g_free (val_allocated);
}
static void
g_slice_init_nomessage (void)
{
/* we may not use g_error() or friends here */
mem_assert (sys_page_size == 0);
mem_assert (MIN_MAGAZINE_SIZE >= 4);
#ifdef G_OS_WIN32
{
SYSTEM_INFO system_info;
GetSystemInfo (&system_info);
sys_page_size = system_info.dwPageSize;
}
#else
sys_page_size = sysconf (_SC_PAGESIZE); /* = sysconf (_SC_PAGE_SIZE); = getpagesize(); */
#endif
mem_assert (sys_page_size >= 2 * LARGEALIGNMENT);
mem_assert ((sys_page_size & (sys_page_size - 1)) == 0);
slice_config_init (&allocator->config);
allocator->min_page_size = sys_page_size;
#if HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN
/* allow allocation of pages up to 8KB (with 8KB alignment).
* this is useful because many medium to large sized structures
* fit less than 8 times (see [4]) into 4KB pages.
* we allow very small page sizes here, to reduce wastage in
* threads if only small allocations are required (this does
* bear the risk of increasing allocation times and fragmentation
* though).
*/
allocator->min_page_size = MAX (allocator->min_page_size, 4096);
allocator->max_page_size = MAX (allocator->min_page_size, 8192);
allocator->min_page_size = MIN (allocator->min_page_size, 128);
#else
/* we can only align to system page size */
allocator->max_page_size = sys_page_size;
#endif
if (allocator->config.always_malloc)
{
allocator->contention_counters = NULL;
allocator->magazines = NULL;
allocator->slab_stack = NULL;
}
else
{
allocator->contention_counters = g_new0 (guint, MAX_SLAB_INDEX (allocator));
allocator->magazines = g_new0 (ChunkLink*, MAX_SLAB_INDEX (allocator));
allocator->slab_stack = g_new0 (SlabInfo*, MAX_SLAB_INDEX (allocator));
}
allocator->mutex_counter = 0;
allocator->stamp_counter = MAX_STAMP_COUNTER; /* force initial update */
allocator->last_stamp = 0;
allocator->color_accu = 0;
magazine_cache_update_stamp();
/* values cached for performance reasons */
allocator->max_slab_chunk_size_for_magazine_cache = MAX_SLAB_CHUNK_SIZE (allocator);
if (allocator->config.always_malloc || allocator->config.bypass_magazines)
allocator->max_slab_chunk_size_for_magazine_cache = 0; /* non-optimized cases */
}
static inline guint
allocator_categorize (gsize aligned_chunk_size)
{
/* speed up the likely path */
if (G_LIKELY (aligned_chunk_size && aligned_chunk_size <= allocator->max_slab_chunk_size_for_magazine_cache))
return 1; /* use magazine cache */
if (!allocator->config.always_malloc &&
aligned_chunk_size &&
aligned_chunk_size <= MAX_SLAB_CHUNK_SIZE (allocator))
{
if (allocator->config.bypass_magazines)
return 2; /* use slab allocator, see [2] */
return 1; /* use magazine cache */
}
return 0; /* use malloc() */
}
static inline void
g_mutex_lock_a (GMutex *mutex,
guint *contention_counter)
{
gboolean contention = FALSE;
if (!g_mutex_trylock (mutex))
{
g_mutex_lock (mutex);
contention = TRUE;
}
if (contention)
{
allocator->mutex_counter++;
if (allocator->mutex_counter >= 1) /* quickly adapt to contention */
{
allocator->mutex_counter = 0;
*contention_counter = MIN (*contention_counter + 1, MAX_MAGAZINE_SIZE);
}
}
else /* !contention */
{
allocator->mutex_counter--;
if (allocator->mutex_counter < -11) /* moderately recover magazine sizes */
{
allocator->mutex_counter = 0;
*contention_counter = MAX (*contention_counter, 1) - 1;
}
}
}
static inline ThreadMemory*
thread_memory_from_self (void)
{
ThreadMemory *tmem = g_private_get (&private_thread_memory);
if (G_UNLIKELY (!tmem))
{
static GMutex init_mutex;
guint n_magazines;
g_mutex_lock (&init_mutex);
if G_UNLIKELY (sys_page_size == 0)
g_slice_init_nomessage ();
g_mutex_unlock (&init_mutex);
n_magazines = MAX_SLAB_INDEX (allocator);
tmem = g_private_set_alloc0 (&private_thread_memory, sizeof (ThreadMemory) + sizeof (Magazine) * 2 * n_magazines);
tmem->magazine1 = (Magazine*) (tmem + 1);
tmem->magazine2 = &tmem->magazine1[n_magazines];
}
return tmem;
}
static inline ChunkLink*
magazine_chain_pop_head (ChunkLink **magazine_chunks)
{
/* magazine chains are linked via ChunkLink->next.
* each ChunkLink->data of the toplevel chain may point to a subchain,
* linked via ChunkLink->next. ChunkLink->data of the subchains just
* contains uninitialized junk.
*/
ChunkLink *chunk = (*magazine_chunks)->data;
if (G_UNLIKELY (chunk))
{
/* allocating from freed list */
(*magazine_chunks)->data = chunk->next;
}
else
{
chunk = *magazine_chunks;
*magazine_chunks = chunk->next;
}
return chunk;
}
#if 0 /* useful for debugging */
static guint
magazine_count (ChunkLink *head)
{
guint count = 0;
if (!head)
return 0;
while (head)
{
ChunkLink *child = head->data;
count += 1;
for (child = head->data; child; child = child->next)
count += 1;
head = head->next;
}
return count;
}
#endif
static inline gsize
allocator_get_magazine_threshold (Allocator *local_allocator,
guint ix)
{
/* the magazine size calculated here has a lower bound of MIN_MAGAZINE_SIZE,
* which is required by the implementation. also, for moderately sized chunks
* (say >= 64 bytes), magazine sizes shouldn't be much smaller then the number
* of chunks available per page/2 to avoid excessive traffic in the magazine
* cache for small to medium sized structures.
* the upper bound of the magazine size is effectively provided by
* MAX_MAGAZINE_SIZE. for larger chunks, this number is scaled down so that
* the content of a single magazine doesn't exceed ca. 16KB.
*/
gsize chunk_size = SLAB_CHUNK_SIZE (local_allocator, ix);
guint threshold = MAX (MIN_MAGAZINE_SIZE, local_allocator->max_page_size / MAX (5 * chunk_size, 5 * 32));
guint contention_counter = local_allocator->contention_counters[ix];
if (G_UNLIKELY (contention_counter)) /* single CPU bias */
{
/* adapt contention counter thresholds to chunk sizes */
contention_counter = contention_counter * 64 / chunk_size;
threshold = MAX (threshold, contention_counter);
}
return threshold;
}
/* --- magazine cache --- */
static inline void
magazine_cache_update_stamp (void)
{
if (allocator->stamp_counter >= MAX_STAMP_COUNTER)
{
gint64 now_us = g_get_real_time ();
allocator->last_stamp = now_us / 1000; /* milli seconds */
allocator->stamp_counter = 0;
}
else
allocator->stamp_counter++;
}
static inline ChunkLink*
magazine_chain_prepare_fields (ChunkLink *magazine_chunks)
{
ChunkLink *chunk1;
ChunkLink *chunk2;
ChunkLink *chunk3;
ChunkLink *chunk4;
/* checked upon initialization: mem_assert (MIN_MAGAZINE_SIZE >= 4); */
/* ensure a magazine with at least 4 unused data pointers */
chunk1 = magazine_chain_pop_head (&magazine_chunks);
chunk2 = magazine_chain_pop_head (&magazine_chunks);
chunk3 = magazine_chain_pop_head (&magazine_chunks);
chunk4 = magazine_chain_pop_head (&magazine_chunks);
chunk4->next = magazine_chunks;
chunk3->next = chunk4;
chunk2->next = chunk3;
chunk1->next = chunk2;
return chunk1;
}
/* access the first 3 fields of a specially prepared magazine chain */
#define magazine_chain_prev(mc) ((mc)->data)
#define magazine_chain_stamp(mc) ((mc)->next->data)
#define magazine_chain_uint_stamp(mc) GPOINTER_TO_UINT ((mc)->next->data)
#define magazine_chain_next(mc) ((mc)->next->next->data)
#define magazine_chain_count(mc) ((mc)->next->next->next->data)
static void
magazine_cache_trim (Allocator *local_allocator,
guint ix,
guint stamp)
{
/* g_mutex_lock (local_allocator->mutex); done by caller */
/* trim magazine cache from tail */
ChunkLink *current = magazine_chain_prev (local_allocator->magazines[ix]);
ChunkLink *trash = NULL;
while (!G_APPROX_VALUE (stamp, magazine_chain_uint_stamp (current),
local_allocator->config.working_set_msecs))
{
/* unlink */
ChunkLink *prev = magazine_chain_prev (current);
ChunkLink *next = magazine_chain_next (current);
magazine_chain_next (prev) = next;
magazine_chain_prev (next) = prev;
/* clear special fields, put on trash stack */
magazine_chain_next (current) = NULL;
magazine_chain_count (current) = NULL;
magazine_chain_stamp (current) = NULL;
magazine_chain_prev (current) = trash;
trash = current;
/* fixup list head if required */
if (current == local_allocator->magazines[ix])
{
local_allocator->magazines[ix] = NULL;
break;
}
current = prev;
}
g_mutex_unlock (&local_allocator->magazine_mutex);
/* free trash */
if (trash)
{
const gsize chunk_size = SLAB_CHUNK_SIZE (local_allocator, ix);
g_mutex_lock (&local_allocator->slab_mutex);
while (trash)
{
current = trash;
trash = magazine_chain_prev (current);
magazine_chain_prev (current) = NULL; /* clear special field */
while (current)
{
ChunkLink *chunk = magazine_chain_pop_head (&current);
slab_allocator_free_chunk (chunk_size, chunk);
}
}
g_mutex_unlock (&local_allocator->slab_mutex);
}
}
static void
magazine_cache_push_magazine (guint ix,
ChunkLink *magazine_chunks,
gsize count) /* must be >= MIN_MAGAZINE_SIZE */
{
ChunkLink *current = magazine_chain_prepare_fields (magazine_chunks);
ChunkLink *next, *prev;
g_mutex_lock (&allocator->magazine_mutex);
/* add magazine at head */
next = allocator->magazines[ix];
if (next)
prev = magazine_chain_prev (next);
else
next = prev = current;
magazine_chain_next (prev) = current;
magazine_chain_prev (next) = current;
magazine_chain_prev (current) = prev;
magazine_chain_next (current) = next;
magazine_chain_count (current) = (gpointer) count;
/* stamp magazine */
magazine_cache_update_stamp();
magazine_chain_stamp (current) = GUINT_TO_POINTER (allocator->last_stamp);
allocator->magazines[ix] = current;
/* free old magazines beyond a certain threshold */
magazine_cache_trim (allocator, ix, allocator->last_stamp);
/* g_mutex_unlock (allocator->mutex); was done by magazine_cache_trim() */
}
static ChunkLink*
magazine_cache_pop_magazine (guint ix,
gsize *countp)
{
g_mutex_lock_a (&allocator->magazine_mutex, &allocator->contention_counters[ix]);
if (!allocator->magazines[ix])
{
guint magazine_threshold = allocator_get_magazine_threshold (allocator, ix);
gsize i, chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
ChunkLink *chunk, *head;
g_mutex_unlock (&allocator->magazine_mutex);
g_mutex_lock (&allocator->slab_mutex);
head = slab_allocator_alloc_chunk (chunk_size);
head->data = NULL;
chunk = head;
for (i = 1; i < magazine_threshold; i++)
{
chunk->next = slab_allocator_alloc_chunk (chunk_size);
chunk = chunk->next;
chunk->data = NULL;
}
chunk->next = NULL;
g_mutex_unlock (&allocator->slab_mutex);
*countp = i;
return head;
}
else
{
ChunkLink *current = allocator->magazines[ix];
ChunkLink *prev = magazine_chain_prev (current);
ChunkLink *next = magazine_chain_next (current);
/* unlink */
magazine_chain_next (prev) = next;
magazine_chain_prev (next) = prev;
allocator->magazines[ix] = next == current ? NULL : next;
g_mutex_unlock (&allocator->magazine_mutex);
/* clear special fields and hand out */
*countp = (gsize) magazine_chain_count (current);
magazine_chain_prev (current) = NULL;
magazine_chain_next (current) = NULL;
magazine_chain_count (current) = NULL;
magazine_chain_stamp (current) = NULL;
return current;
}
}
/* --- thread magazines --- */
static void
private_thread_memory_cleanup (gpointer data)
{
ThreadMemory *tmem = data;
const guint n_magazines = MAX_SLAB_INDEX (allocator);
guint ix;
for (ix = 0; ix < n_magazines; ix++)
{
Magazine *mags[2];
guint j;
mags[0] = &tmem->magazine1[ix];
mags[1] = &tmem->magazine2[ix];
for (j = 0; j < 2; j++)
{
Magazine *mag = mags[j];
if (mag->count >= MIN_MAGAZINE_SIZE)
magazine_cache_push_magazine (ix, mag->chunks, mag->count);
else
{
const gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
g_mutex_lock (&allocator->slab_mutex);
while (mag->chunks)
{
ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks);
slab_allocator_free_chunk (chunk_size, chunk);
}
g_mutex_unlock (&allocator->slab_mutex);
}
}
}
g_free (tmem);
}
static void
thread_memory_magazine1_reload (ThreadMemory *tmem,
guint ix)
{
Magazine *mag = &tmem->magazine1[ix];
mem_assert (mag->chunks == NULL); /* ensure that we may reset mag->count */
mag->count = 0;
mag->chunks = magazine_cache_pop_magazine (ix, &mag->count);
}
static void
thread_memory_magazine2_unload (ThreadMemory *tmem,
guint ix)
{
Magazine *mag = &tmem->magazine2[ix];
magazine_cache_push_magazine (ix, mag->chunks, mag->count);
mag->chunks = NULL;
mag->count = 0;
}
static inline void
thread_memory_swap_magazines (ThreadMemory *tmem,
guint ix)
{
Magazine xmag = tmem->magazine1[ix];
tmem->magazine1[ix] = tmem->magazine2[ix];
tmem->magazine2[ix] = xmag;
}
static inline gboolean
thread_memory_magazine1_is_empty (ThreadMemory *tmem,
guint ix)
{
return tmem->magazine1[ix].chunks == NULL;
}
static inline gboolean
thread_memory_magazine2_is_full (ThreadMemory *tmem,
guint ix)
{
return tmem->magazine2[ix].count >= allocator_get_magazine_threshold (allocator, ix);
}
static inline gpointer
thread_memory_magazine1_alloc (ThreadMemory *tmem,
guint ix)
{
Magazine *mag = &tmem->magazine1[ix];
ChunkLink *chunk = magazine_chain_pop_head (&mag->chunks);
if (G_LIKELY (mag->count > 0))
mag->count--;
return chunk;
}
static inline void
thread_memory_magazine2_free (ThreadMemory *tmem,
guint ix,
gpointer mem)
{
Magazine *mag = &tmem->magazine2[ix];
ChunkLink *chunk = mem;
chunk->data = NULL;
chunk->next = mag->chunks;
mag->chunks = chunk;
mag->count++;
}
/* --- API functions --- */
/**
* g_slice_new:
* @type: the type to allocate, typically a structure name
*
* A convenience macro to allocate a block of memory from the
* slice allocator.
*
* It calls g_slice_alloc() with `sizeof (@type)` and casts the
* returned pointer to a pointer of the given type, avoiding a type
* cast in the source code. Note that the underlying slice allocation
* mechanism can be changed with the [`G_SLICE=always-malloc`][G_SLICE]
* environment variable.
*
* This can never return %NULL as the minimum allocation size from
* `sizeof (@type)` is 1 byte.
*
* Returns: (not nullable): a pointer to the allocated block, cast to a pointer
* to @type
*
* Since: 2.10
*/
/**
* g_slice_new0:
* @type: the type to allocate, typically a structure name
*
* A convenience macro to allocate a block of memory from the
* slice allocator and set the memory to 0.
*
* It calls g_slice_alloc0() with `sizeof (@type)`
* and casts the returned pointer to a pointer of the given type,
* avoiding a type cast in the source code.
* Note that the underlying slice allocation mechanism can
* be changed with the [`G_SLICE=always-malloc`][G_SLICE]
* environment variable.
*
* This can never return %NULL as the minimum allocation size from
* `sizeof (@type)` is 1 byte.
*
* Returns: (not nullable): a pointer to the allocated block, cast to a pointer
* to @type
*
* Since: 2.10
*/
/**
* g_slice_dup:
* @type: the type to duplicate, typically a structure name
* @mem: (not nullable): the memory to copy into the allocated block
*
* A convenience macro to duplicate a block of memory using
* the slice allocator.
*
* It calls g_slice_copy() with `sizeof (@type)`
* and casts the returned pointer to a pointer of the given type,
* avoiding a type cast in the source code.
* Note that the underlying slice allocation mechanism can
* be changed with the [`G_SLICE=always-malloc`][G_SLICE]
* environment variable.
*
* This can never return %NULL.
*
* Returns: (not nullable): a pointer to the allocated block, cast to a pointer
* to @type
*
* Since: 2.14
*/
/**
* g_slice_free:
* @type: the type of the block to free, typically a structure name
* @mem: a pointer to the block to free
*
* A convenience macro to free a block of memory that has
* been allocated from the slice allocator.
*
* It calls g_slice_free1() using `sizeof (type)`
* as the block size.
* Note that the exact release behaviour can be changed with the
* [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable, also see
* [`G_SLICE`][G_SLICE] for related debugging options.
*
* If @mem is %NULL, this macro does nothing.
*
* Since: 2.10
*/
/**
* g_slice_free_chain:
* @type: the type of the @mem_chain blocks
* @mem_chain: a pointer to the first block of the chain
* @next: the field name of the next pointer in @type
*
* Frees a linked list of memory blocks of structure type @type.
*
* The memory blocks must be equal-sized, allocated via
* g_slice_alloc() or g_slice_alloc0() and linked together by
* a @next pointer (similar to #GSList). The name of the
* @next field in @type is passed as third argument.
* Note that the exact release behaviour can be changed with the
* [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable, also see
* [`G_SLICE`][G_SLICE] for related debugging options.
*
* If @mem_chain is %NULL, this function does nothing.
*
* Since: 2.10
*/
/**
* g_slice_alloc:
* @block_size: the number of bytes to allocate
*
* Allocates a block of memory from the slice allocator.
*
* The block address handed out can be expected to be aligned
* to at least `1 * sizeof (void*)`, though in general slices
* are `2 * sizeof (void*)` bytes aligned; if a `malloc()`
* fallback implementation is used instead, the alignment may
* be reduced in a libc dependent fashion.
*
* Note that the underlying slice allocation mechanism can
* be changed with the [`G_SLICE=always-malloc`][G_SLICE]
* environment variable.
*
* Returns: a pointer to the allocated memory block, which will
* be %NULL if and only if @mem_size is 0
*
* Since: 2.10
*/
gpointer
g_slice_alloc (gsize mem_size)
{
ThreadMemory *tmem;
gsize chunk_size;
gpointer mem;
guint acat;
/* This gets the private structure for this thread. If the private
* structure does not yet exist, it is created.
*
* This has a side effect of causing GSlice to be initialised, so it
* must come first.
*/
tmem = thread_memory_from_self ();
chunk_size = P2ALIGN (mem_size);
acat = allocator_categorize (chunk_size);
if (G_LIKELY (acat == 1)) /* allocate through magazine layer */
{
guint ix = SLAB_INDEX (allocator, chunk_size);
if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix)))
{
thread_memory_swap_magazines (tmem, ix);
if (G_UNLIKELY (thread_memory_magazine1_is_empty (tmem, ix)))
thread_memory_magazine1_reload (tmem, ix);
}
mem = thread_memory_magazine1_alloc (tmem, ix);
}
else if (acat == 2) /* allocate through slab allocator */
{
g_mutex_lock (&allocator->slab_mutex);
mem = slab_allocator_alloc_chunk (chunk_size);
g_mutex_unlock (&allocator->slab_mutex);
}
else /* delegate to system malloc */
mem = g_malloc (mem_size);
if (G_UNLIKELY (allocator->config.debug_blocks))
smc_notify_alloc (mem, mem_size);
TRACE (GLIB_SLICE_ALLOC((void*)mem, mem_size));
return mem;
}
/**
* g_slice_alloc0:
* @block_size: the number of bytes to allocate
*
* Allocates a block of memory via g_slice_alloc() and initializes
* the returned memory to 0. Note that the underlying slice allocation
* mechanism can be changed with the [`G_SLICE=always-malloc`][G_SLICE]
* environment variable.
*
* Returns: a pointer to the allocated block, which will be %NULL if and only
* if @mem_size is 0
*
* Since: 2.10
*/
gpointer
g_slice_alloc0 (gsize mem_size)
{
gpointer mem = g_slice_alloc (mem_size);
if (mem)
memset (mem, 0, mem_size);
return mem;
}
/**
* g_slice_copy:
* @block_size: the number of bytes to allocate
* @mem_block: the memory to copy
*
* Allocates a block of memory from the slice allocator
* and copies @block_size bytes into it from @mem_block.
*
* @mem_block must be non-%NULL if @block_size is non-zero.
*
* Returns: a pointer to the allocated memory block, which will be %NULL if and
* only if @mem_size is 0
*
* Since: 2.14
*/
gpointer
g_slice_copy (gsize mem_size,
gconstpointer mem_block)
{
gpointer mem = g_slice_alloc (mem_size);
if (mem)
memcpy (mem, mem_block, mem_size);
return mem;
}
/**
* g_slice_free1:
* @block_size: the size of the block
* @mem_block: a pointer to the block to free
*
* Frees a block of memory.
*
* The memory must have been allocated via g_slice_alloc() or
* g_slice_alloc0() and the @block_size has to match the size
* specified upon allocation. Note that the exact release behaviour
* can be changed with the [`G_DEBUG=gc-friendly`][G_DEBUG] environment
* variable, also see [`G_SLICE`][G_SLICE] for related debugging options.
*
* If @mem_block is %NULL, this function does nothing.
*
* Since: 2.10
*/
void
g_slice_free1 (gsize mem_size,
gpointer mem_block)
{
gsize chunk_size = P2ALIGN (mem_size);
guint acat = allocator_categorize (chunk_size);
if (G_UNLIKELY (!mem_block))
return;
if (G_UNLIKELY (allocator->config.debug_blocks) &&
!smc_notify_free (mem_block, mem_size))
abort();
if (G_LIKELY (acat == 1)) /* allocate through magazine layer */
{
ThreadMemory *tmem = thread_memory_from_self();
guint ix = SLAB_INDEX (allocator, chunk_size);
if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
{
thread_memory_swap_magazines (tmem, ix);
if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
thread_memory_magazine2_unload (tmem, ix);
}
if (G_UNLIKELY (g_mem_gc_friendly))
memset (mem_block, 0, chunk_size);
thread_memory_magazine2_free (tmem, ix, mem_block);
}
else if (acat == 2) /* allocate through slab allocator */
{
if (G_UNLIKELY (g_mem_gc_friendly))
memset (mem_block, 0, chunk_size);
g_mutex_lock (&allocator->slab_mutex);
slab_allocator_free_chunk (chunk_size, mem_block);
g_mutex_unlock (&allocator->slab_mutex);
}
else /* delegate to system malloc */
{
if (G_UNLIKELY (g_mem_gc_friendly))
memset (mem_block, 0, mem_size);
g_free (mem_block);
}
TRACE (GLIB_SLICE_FREE((void*)mem_block, mem_size));
}
/**
* g_slice_free_chain_with_offset:
* @block_size: the size of the blocks
* @mem_chain: a pointer to the first block of the chain
* @next_offset: the offset of the @next field in the blocks
*
* Frees a linked list of memory blocks of structure type @type.
*
* The memory blocks must be equal-sized, allocated via
* g_slice_alloc() or g_slice_alloc0() and linked together by a
* @next pointer (similar to #GSList). The offset of the @next
* field in each block is passed as third argument.
* Note that the exact release behaviour can be changed with the
* [`G_DEBUG=gc-friendly`][G_DEBUG] environment variable, also see
* [`G_SLICE`][G_SLICE] for related debugging options.
*
* If @mem_chain is %NULL, this function does nothing.
*
* Since: 2.10
*/
void
g_slice_free_chain_with_offset (gsize mem_size,
gpointer mem_chain,
gsize next_offset)
{
gpointer slice = mem_chain;
/* while the thread magazines and the magazine cache are implemented so that
* they can easily be extended to allow for free lists containing more free
* lists for the first level nodes, which would allow O(1) freeing in this
* function, the benefit of such an extension is questionable, because:
* - the magazine size counts will become mere lower bounds which confuses
* the code adapting to lock contention;
* - freeing a single node to the thread magazines is very fast, so this
* O(list_length) operation is multiplied by a fairly small factor;
* - memory usage histograms on larger applications seem to indicate that
* the amount of released multi node lists is negligible in comparison
* to single node releases.
* - the major performance bottle neck, namely g_private_get() or
* g_mutex_lock()/g_mutex_unlock() has already been moved out of the
* inner loop for freeing chained slices.
*/
gsize chunk_size = P2ALIGN (mem_size);
guint acat = allocator_categorize (chunk_size);
if (G_LIKELY (acat == 1)) /* allocate through magazine layer */
{
ThreadMemory *tmem = thread_memory_from_self();
guint ix = SLAB_INDEX (allocator, chunk_size);
while (slice)
{
guint8 *current = slice;
slice = *(gpointer*) (current + next_offset);
if (G_UNLIKELY (allocator->config.debug_blocks) &&
!smc_notify_free (current, mem_size))
abort();
if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
{
thread_memory_swap_magazines (tmem, ix);
if (G_UNLIKELY (thread_memory_magazine2_is_full (tmem, ix)))
thread_memory_magazine2_unload (tmem, ix);
}
if (G_UNLIKELY (g_mem_gc_friendly))
memset (current, 0, chunk_size);
thread_memory_magazine2_free (tmem, ix, current);
}
}
else if (acat == 2) /* allocate through slab allocator */
{
g_mutex_lock (&allocator->slab_mutex);
while (slice)
{
guint8 *current = slice;
slice = *(gpointer*) (current + next_offset);
if (G_UNLIKELY (allocator->config.debug_blocks) &&
!smc_notify_free (current, mem_size))
abort();
if (G_UNLIKELY (g_mem_gc_friendly))
memset (current, 0, chunk_size);
slab_allocator_free_chunk (chunk_size, current);
}
g_mutex_unlock (&allocator->slab_mutex);
}
else /* delegate to system malloc */
while (slice)
{
guint8 *current = slice;
slice = *(gpointer*) (current + next_offset);
if (G_UNLIKELY (allocator->config.debug_blocks) &&
!smc_notify_free (current, mem_size))
abort();
if (G_UNLIKELY (g_mem_gc_friendly))
memset (current, 0, mem_size);
g_free (current);
}
}
/* --- single page allocator --- */
static void
allocator_slab_stack_push (Allocator *local_allocator,
guint ix,
SlabInfo *sinfo)
{
/* insert slab at slab ring head */
if (!local_allocator->slab_stack[ix])
{
sinfo->next = sinfo;
sinfo->prev = sinfo;
}
else
{
SlabInfo *next = local_allocator->slab_stack[ix], *prev = next->prev;
next->prev = sinfo;
prev->next = sinfo;
sinfo->next = next;
sinfo->prev = prev;
}
local_allocator->slab_stack[ix] = sinfo;
}
static gsize
allocator_aligned_page_size (Allocator *local_allocator,
gsize n_bytes)
{
gsize val = (gsize) 1 << g_bit_storage (n_bytes - 1);
val = MAX (val, local_allocator->min_page_size);
return val;
}
static void
allocator_add_slab (Allocator *local_allocator,
guint ix,
gsize chunk_size)
{
ChunkLink *chunk;
SlabInfo *sinfo;
gsize addr, padding, n_chunks, color = 0;
gsize page_size;
int errsv;
gpointer aligned_memory;
guint8 *mem;
guint i;
page_size = allocator_aligned_page_size (local_allocator, SLAB_BPAGE_SIZE (local_allocator, chunk_size));
/* allocate 1 page for the chunks and the slab */
aligned_memory = allocator_memalign (page_size, page_size - NATIVE_MALLOC_PADDING);
errsv = errno;
mem = aligned_memory;
if (!mem)
{
const gchar *syserr = strerror (errsv);
mem_error ("failed to allocate %u bytes (alignment: %u): %s\n",
(guint) (page_size - NATIVE_MALLOC_PADDING), (guint) page_size, syserr);
}
/* mask page address */
addr = ((gsize) mem / page_size) * page_size;
/* assert alignment */
mem_assert (aligned_memory == (gpointer) addr);
/* basic slab info setup */
sinfo = (SlabInfo*) (mem + page_size - SLAB_INFO_SIZE);
sinfo->n_allocated = 0;
sinfo->chunks = NULL;
/* figure cache colorization */
n_chunks = ((guint8*) sinfo - mem) / chunk_size;
padding = ((guint8*) sinfo - mem) - n_chunks * chunk_size;
if (padding)
{
color = (local_allocator->color_accu * P2ALIGNMENT) % padding;
local_allocator->color_accu += local_allocator->config.color_increment;
}
/* add chunks to free list */
chunk = (ChunkLink*) (mem + color);
sinfo->chunks = chunk;
for (i = 0; i < n_chunks - 1; i++)
{
chunk->next = (ChunkLink*) ((guint8*) chunk + chunk_size);
chunk = chunk->next;
}
chunk->next = NULL; /* last chunk */
/* add slab to slab ring */
allocator_slab_stack_push (local_allocator, ix, sinfo);
}
static gpointer
slab_allocator_alloc_chunk (gsize chunk_size)
{
ChunkLink *chunk;
guint ix = SLAB_INDEX (allocator, chunk_size);
/* ensure non-empty slab */
if (!allocator->slab_stack[ix] || !allocator->slab_stack[ix]->chunks)
allocator_add_slab (allocator, ix, chunk_size);
/* allocate chunk */
chunk = allocator->slab_stack[ix]->chunks;
allocator->slab_stack[ix]->chunks = chunk->next;
allocator->slab_stack[ix]->n_allocated++;
/* rotate empty slabs */
if (!allocator->slab_stack[ix]->chunks)
allocator->slab_stack[ix] = allocator->slab_stack[ix]->next;
return chunk;
}
static void
slab_allocator_free_chunk (gsize chunk_size,
gpointer mem)
{
ChunkLink *chunk;
gboolean was_empty;
guint ix = SLAB_INDEX (allocator, chunk_size);
gsize page_size = allocator_aligned_page_size (allocator, SLAB_BPAGE_SIZE (allocator, chunk_size));
gsize addr = ((gsize) mem / page_size) * page_size;
/* mask page address */
guint8 *page = (guint8*) addr;
SlabInfo *sinfo = (SlabInfo*) (page + page_size - SLAB_INFO_SIZE);
/* assert valid chunk count */
mem_assert (sinfo->n_allocated > 0);
/* add chunk to free list */
was_empty = sinfo->chunks == NULL;
chunk = (ChunkLink*) mem;
chunk->next = sinfo->chunks;
sinfo->chunks = chunk;
sinfo->n_allocated--;
/* keep slab ring partially sorted, empty slabs at end */
if (was_empty)
{
/* unlink slab */
SlabInfo *next = sinfo->next, *prev = sinfo->prev;
next->prev = prev;
prev->next = next;
if (allocator->slab_stack[ix] == sinfo)
allocator->slab_stack[ix] = next == sinfo ? NULL : next;
/* insert slab at head */
allocator_slab_stack_push (allocator, ix, sinfo);
}
/* eagerly free complete unused slabs */
if (!sinfo->n_allocated)
{
/* unlink slab */
SlabInfo *next = sinfo->next, *prev = sinfo->prev;
next->prev = prev;
prev->next = next;
if (allocator->slab_stack[ix] == sinfo)
allocator->slab_stack[ix] = next == sinfo ? NULL : next;
/* free slab */
allocator_memfree (page_size, page);
}
}
/* --- memalign implementation --- */
#ifdef HAVE_MALLOC_H
#include <malloc.h> /* memalign() */
#endif
/* from config.h:
* define HAVE_POSIX_MEMALIGN 1 // if free(posix_memalign(3)) works, <stdlib.h>
* define HAVE_MEMALIGN 1 // if free(memalign(3)) works, <malloc.h>
* define HAVE_VALLOC 1 // if free(valloc(3)) works, <stdlib.h> or <malloc.h>
* if none is provided, we implement malloc(3)-based alloc-only page alignment
*/
#if !(HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC)
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
static GTrashStack *compat_valloc_trash = NULL;
G_GNUC_END_IGNORE_DEPRECATIONS
#endif
static gpointer
allocator_memalign (gsize alignment,
gsize memsize)
{
gpointer aligned_memory = NULL;
gint err = ENOMEM;
#if HAVE_POSIX_MEMALIGN
err = posix_memalign (&aligned_memory, alignment, memsize);
#elif HAVE_MEMALIGN
errno = 0;
aligned_memory = memalign (alignment, memsize);
err = errno;
#elif HAVE_VALLOC
errno = 0;
aligned_memory = valloc (memsize);
err = errno;
#else
/* simplistic non-freeing page allocator */
mem_assert (alignment == sys_page_size);
mem_assert (memsize <= sys_page_size);
if (!compat_valloc_trash)
{
const guint n_pages = 16;
guint8 *mem = malloc (n_pages * sys_page_size);
err = errno;
if (mem)
{
gint i = n_pages;
guint8 *amem = (guint8*) ALIGN ((gsize) mem, sys_page_size);
if (amem != mem)
i--; /* mem wasn't page aligned */
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
while (--i >= 0)
g_trash_stack_push (&compat_valloc_trash, amem + i * sys_page_size);
G_GNUC_END_IGNORE_DEPRECATIONS
}
}
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
aligned_memory = g_trash_stack_pop (&compat_valloc_trash);
G_GNUC_END_IGNORE_DEPRECATIONS
#endif
if (!aligned_memory)
errno = err;
return aligned_memory;
}
static void
allocator_memfree (gsize memsize,
gpointer mem)
{
#if HAVE_POSIX_MEMALIGN || HAVE_MEMALIGN || HAVE_VALLOC
free (mem);
#else
mem_assert (memsize <= sys_page_size);
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
g_trash_stack_push (&compat_valloc_trash, mem);
G_GNUC_END_IGNORE_DEPRECATIONS
#endif
}
static void
mem_error (const char *format,
...)
{
const char *pname;
va_list args;
/* at least, put out "MEMORY-ERROR", in case we segfault during the rest of the function */
fputs ("\n***MEMORY-ERROR***: ", stderr);
pname = g_get_prgname();
g_fprintf (stderr, "%s[%ld]: GSlice: ", pname ? pname : "", (long)getpid());
va_start (args, format);
g_vfprintf (stderr, format, args);
va_end (args);
fputs ("\n", stderr);
abort();
_exit (1);
}
/* --- g-slice memory checker tree --- */
typedef size_t SmcKType; /* key type */
typedef size_t SmcVType; /* value type */
typedef struct {
SmcKType key;
SmcVType value;
} SmcEntry;
static void smc_tree_insert (SmcKType key,
SmcVType value);
static gboolean smc_tree_lookup (SmcKType key,
SmcVType *value_p);
static gboolean smc_tree_remove (SmcKType key);
/* --- g-slice memory checker implementation --- */
static void
smc_notify_alloc (void *pointer,
size_t size)
{
size_t address = (size_t) pointer;
if (pointer)
smc_tree_insert (address, size);
}
#if 0
static void
smc_notify_ignore (void *pointer)
{
size_t address = (size_t) pointer;
if (pointer)
smc_tree_remove (address);
}
#endif
static int
smc_notify_free (void *pointer,
size_t size)
{
size_t address = (size_t) pointer;
SmcVType real_size;
gboolean found_one;
if (!pointer)
return 1; /* ignore */
found_one = smc_tree_lookup (address, &real_size);
if (!found_one)
{
g_fprintf (stderr, "GSlice: MemChecker: attempt to release non-allocated block: %p size=%" G_GSIZE_FORMAT "\n", pointer, size);
return 0;
}
if (real_size != size && (real_size || size))
{
g_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);
return 0;
}
if (!smc_tree_remove (address))
{
g_fprintf (stderr, "GSlice: MemChecker: attempt to release non-allocated block: %p size=%" G_GSIZE_FORMAT "\n", pointer, size);
return 0;
}
return 1; /* all fine */
}
/* --- g-slice memory checker tree implementation --- */
#define SMC_TRUNK_COUNT (4093 /* 16381 */) /* prime, to distribute trunk collisions (big, allocated just once) */
#define SMC_BRANCH_COUNT (511) /* prime, to distribute branch collisions */
#define SMC_TRUNK_EXTENT (SMC_BRANCH_COUNT * 2039) /* key address space per trunk, should distribute uniformly across BRANCH_COUNT */
#define SMC_TRUNK_HASH(k) ((k / SMC_TRUNK_EXTENT) % SMC_TRUNK_COUNT) /* generate new trunk hash per megabyte (roughly) */
#define SMC_BRANCH_HASH(k) (k % SMC_BRANCH_COUNT)
typedef struct {
SmcEntry *entries;
unsigned int n_entries;
} SmcBranch;
static SmcBranch **smc_tree_root = NULL;
static void
smc_tree_abort (int errval)
{
const char *syserr = strerror (errval);
mem_error ("MemChecker: failure in debugging tree: %s", syserr);
}
static inline SmcEntry*
smc_tree_branch_grow_L (SmcBranch *branch,
unsigned int index)
{
unsigned int old_size = branch->n_entries * sizeof (branch->entries[0]);
unsigned int new_size = old_size + sizeof (branch->entries[0]);
SmcEntry *entry;
mem_assert (index <= branch->n_entries);
branch->entries = (SmcEntry*) realloc (branch->entries, new_size);
if (!branch->entries)
smc_tree_abort (errno);
entry = branch->entries + index;
memmove (entry + 1, entry, (branch->n_entries - index) * sizeof (entry[0]));
branch->n_entries += 1;
return entry;
}
static inline SmcEntry*
smc_tree_branch_lookup_nearest_L (SmcBranch *branch,
SmcKType key)
{
unsigned int n_nodes = branch->n_entries, offs = 0;
SmcEntry *check = branch->entries;
int cmp = 0;
while (offs < n_nodes)
{
unsigned int i = (offs + n_nodes) >> 1;
check = branch->entries + i;
cmp = key < check->key ? -1 : key != check->key;
if (cmp == 0)
return check; /* return exact match */
else if (cmp < 0)
n_nodes = i;
else /* (cmp > 0) */
offs = i + 1;
}
/* check points at last mismatch, cmp > 0 indicates greater key */
return cmp > 0 ? check + 1 : check; /* return insertion position for inexact match */
}
static void
smc_tree_insert (SmcKType key,
SmcVType value)
{
unsigned int ix0, ix1;
SmcEntry *entry;
g_mutex_lock (&smc_tree_mutex);
ix0 = SMC_TRUNK_HASH (key);
ix1 = SMC_BRANCH_HASH (key);
if (!smc_tree_root)
{
smc_tree_root = calloc (SMC_TRUNK_COUNT, sizeof (smc_tree_root[0]));
if (!smc_tree_root)
smc_tree_abort (errno);
}
if (!smc_tree_root[ix0])
{
smc_tree_root[ix0] = calloc (SMC_BRANCH_COUNT, sizeof (smc_tree_root[0][0]));
if (!smc_tree_root[ix0])
smc_tree_abort (errno);
}
entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
if (!entry || /* need create */
entry >= smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries || /* need append */
entry->key != key) /* need insert */
entry = smc_tree_branch_grow_L (&smc_tree_root[ix0][ix1], entry - smc_tree_root[ix0][ix1].entries);
entry->key = key;
entry->value = value;
g_mutex_unlock (&smc_tree_mutex);
}
static gboolean
smc_tree_lookup (SmcKType key,
SmcVType *value_p)
{
SmcEntry *entry = NULL;
unsigned int ix0 = SMC_TRUNK_HASH (key), ix1 = SMC_BRANCH_HASH (key);
gboolean found_one = FALSE;
*value_p = 0;
g_mutex_lock (&smc_tree_mutex);
if (smc_tree_root && smc_tree_root[ix0])
{
entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
if (entry &&
entry < smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries &&
entry->key == key)
{
found_one = TRUE;
*value_p = entry->value;
}
}
g_mutex_unlock (&smc_tree_mutex);
return found_one;
}
static gboolean
smc_tree_remove (SmcKType key)
{
unsigned int ix0 = SMC_TRUNK_HASH (key), ix1 = SMC_BRANCH_HASH (key);
gboolean found_one = FALSE;
g_mutex_lock (&smc_tree_mutex);
if (smc_tree_root && smc_tree_root[ix0])
{
SmcEntry *entry = smc_tree_branch_lookup_nearest_L (&smc_tree_root[ix0][ix1], key);
if (entry &&
entry < smc_tree_root[ix0][ix1].entries + smc_tree_root[ix0][ix1].n_entries &&
entry->key == key)
{
unsigned int i = entry - smc_tree_root[ix0][ix1].entries;
smc_tree_root[ix0][ix1].n_entries -= 1;
memmove (entry, entry + 1, (smc_tree_root[ix0][ix1].n_entries - i) * sizeof (entry[0]));
if (!smc_tree_root[ix0][ix1].n_entries)
{
/* avoid useless pressure on the memory system */
free (smc_tree_root[ix0][ix1].entries);
smc_tree_root[ix0][ix1].entries = NULL;
}
found_one = TRUE;
}
}
g_mutex_unlock (&smc_tree_mutex);
return found_one;
}
#ifdef G_ENABLE_DEBUG
void
g_slice_debug_tree_statistics (void)
{
g_mutex_lock (&smc_tree_mutex);
if (smc_tree_root)
{
unsigned int i, j, t = 0, o = 0, b = 0, su = 0, ex = 0, en = 4294967295u;
double tf, bf;
for (i = 0; i < SMC_TRUNK_COUNT; i++)
if (smc_tree_root[i])
{
t++;
for (j = 0; j < SMC_BRANCH_COUNT; j++)
if (smc_tree_root[i][j].n_entries)
{
b++;
su += smc_tree_root[i][j].n_entries;
en = MIN (en, smc_tree_root[i][j].n_entries);
ex = MAX (ex, smc_tree_root[i][j].n_entries);
}
else if (smc_tree_root[i][j].entries)
o++; /* formerly used, now empty */
}
en = b ? en : 0;
tf = MAX (t, 1.0); /* max(1) to be a valid divisor */
bf = MAX (b, 1.0); /* max(1) to be a valid divisor */
g_fprintf (stderr, "GSlice: MemChecker: %u trunks, %u branches, %u old branches\n", t, b, o);
g_fprintf (stderr, "GSlice: MemChecker: %f branches per trunk, %.2f%% utilization\n",
b / tf,
100.0 - (SMC_BRANCH_COUNT - b / tf) / (0.01 * SMC_BRANCH_COUNT));
g_fprintf (stderr, "GSlice: MemChecker: %f entries per branch, %u minimum, %u maximum\n",
su / bf, en, ex);
}
else
g_fprintf (stderr, "GSlice: MemChecker: root=NULL\n");
g_mutex_unlock (&smc_tree_mutex);
/* sample statistics (beast + GSLice + 24h scripted core & GUI activity):
* PID %CPU %MEM VSZ RSS COMMAND
* 8887 30.3 45.8 456068 414856 beast-0.7.1 empty.bse
* $ cat /proc/8887/statm # total-program-size resident-set-size shared-pages text/code data/stack library dirty-pages
* 114017 103714 2354 344 0 108676 0
* $ cat /proc/8887/status
* Name: beast-0.7.1
* VmSize: 456068 kB
* VmLck: 0 kB
* VmRSS: 414856 kB
* VmData: 434620 kB
* VmStk: 84 kB
* VmExe: 1376 kB
* VmLib: 13036 kB
* VmPTE: 456 kB
* Threads: 3
* (gdb) print g_slice_debug_tree_statistics ()
* GSlice: MemChecker: 422 trunks, 213068 branches, 0 old branches
* GSlice: MemChecker: 504.900474 branches per trunk, 98.81% utilization
* GSlice: MemChecker: 4.965039 entries per branch, 1 minimum, 37 maximum
*/
}
#endif /* G_ENABLE_DEBUG */
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