1028 lines
30 KiB
C
1028 lines
30 KiB
C
/* Malloc implementation for multiple threads without lock contention.
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Copyright (C) 2001-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, see <https://www.gnu.org/licenses/>. */
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#include <stdbool.h>
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#if HAVE_TUNABLES
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# define TUNABLE_NAMESPACE malloc
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#endif
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#include <elf/dl-tunables.h>
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/* Compile-time constants. */
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#define HEAP_MIN_SIZE (32 * 1024)
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#ifndef HEAP_MAX_SIZE
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# ifdef DEFAULT_MMAP_THRESHOLD_MAX
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# define HEAP_MAX_SIZE (2 * DEFAULT_MMAP_THRESHOLD_MAX)
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# else
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# define HEAP_MAX_SIZE (1024 * 1024) /* must be a power of two */
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# endif
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#endif
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/* HEAP_MIN_SIZE and HEAP_MAX_SIZE limit the size of mmap()ed heaps
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that are dynamically created for multi-threaded programs. The
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maximum size must be a power of two, for fast determination of
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which heap belongs to a chunk. It should be much larger than the
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mmap threshold, so that requests with a size just below that
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threshold can be fulfilled without creating too many heaps. */
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/* When huge pages are used to create new arenas, the maximum and minumum
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size are based on the runtime defined huge page size. */
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static inline size_t
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heap_min_size (void)
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{
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#if HAVE_TUNABLES
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return mp_.hp_pagesize == 0 ? HEAP_MIN_SIZE : mp_.hp_pagesize;
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#else
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return HEAP_MIN_SIZE;
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#endif
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}
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static inline size_t
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heap_max_size (void)
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{
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#if HAVE_TUNABLES
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return mp_.hp_pagesize == 0 ? HEAP_MAX_SIZE : mp_.hp_pagesize * 4;
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#else
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return HEAP_MAX_SIZE;
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#endif
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}
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/***************************************************************************/
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#define top(ar_ptr) ((ar_ptr)->top)
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/* A heap is a single contiguous memory region holding (coalesceable)
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malloc_chunks. It is allocated with mmap() and always starts at an
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address aligned to HEAP_MAX_SIZE. */
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typedef struct _heap_info
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{
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mstate ar_ptr; /* Arena for this heap. */
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struct _heap_info *prev; /* Previous heap. */
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size_t size; /* Current size in bytes. */
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size_t mprotect_size; /* Size in bytes that has been mprotected
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PROT_READ|PROT_WRITE. */
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size_t pagesize; /* Page size used when allocating the arena. */
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/* Make sure the following data is properly aligned, particularly
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that sizeof (heap_info) + 2 * SIZE_SZ is a multiple of
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MALLOC_ALIGNMENT. */
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char pad[-3 * SIZE_SZ & MALLOC_ALIGN_MASK];
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} heap_info;
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/* Get a compile-time error if the heap_info padding is not correct
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to make alignment work as expected in sYSMALLOc. */
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extern int sanity_check_heap_info_alignment[(sizeof (heap_info)
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+ 2 * SIZE_SZ) % MALLOC_ALIGNMENT
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? -1 : 1];
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/* Thread specific data. */
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static __thread mstate thread_arena attribute_tls_model_ie;
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/* Arena free list. free_list_lock synchronizes access to the
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free_list variable below, and the next_free and attached_threads
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members of struct malloc_state objects. No other locks must be
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acquired after free_list_lock has been acquired. */
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__libc_lock_define_initialized (static, free_list_lock);
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#if IS_IN (libc)
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static size_t narenas = 1;
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#endif
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static mstate free_list;
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/* list_lock prevents concurrent writes to the next member of struct
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malloc_state objects.
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Read access to the next member is supposed to synchronize with the
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atomic_write_barrier and the write to the next member in
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_int_new_arena. This suffers from data races; see the FIXME
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comments in _int_new_arena and reused_arena.
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list_lock also prevents concurrent forks. At the time list_lock is
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acquired, no arena lock must have been acquired, but it is
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permitted to acquire arena locks subsequently, while list_lock is
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acquired. */
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__libc_lock_define_initialized (static, list_lock);
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/* Already initialized? */
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static bool __malloc_initialized = false;
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/**************************************************************************/
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/* arena_get() acquires an arena and locks the corresponding mutex.
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First, try the one last locked successfully by this thread. (This
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is the common case and handled with a macro for speed.) Then, loop
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once over the circularly linked list of arenas. If no arena is
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readily available, create a new one. In this latter case, `size'
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is just a hint as to how much memory will be required immediately
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in the new arena. */
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#define arena_get(ptr, size) do { \
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ptr = thread_arena; \
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arena_lock (ptr, size); \
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} while (0)
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#define arena_lock(ptr, size) do { \
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if (ptr) \
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__libc_lock_lock (ptr->mutex); \
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else \
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ptr = arena_get2 ((size), NULL); \
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} while (0)
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/* find the heap and corresponding arena for a given ptr */
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static inline heap_info *
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heap_for_ptr (void *ptr)
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{
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size_t max_size = heap_max_size ();
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return PTR_ALIGN_DOWN (ptr, max_size);
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}
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static inline struct malloc_state *
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arena_for_chunk (mchunkptr ptr)
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{
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return chunk_main_arena (ptr) ? &main_arena : heap_for_ptr (ptr)->ar_ptr;
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}
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/**************************************************************************/
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/* atfork support. */
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/* The following three functions are called around fork from a
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multi-threaded process. We do not use the general fork handler
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mechanism to make sure that our handlers are the last ones being
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called, so that other fork handlers can use the malloc
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subsystem. */
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void
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__malloc_fork_lock_parent (void)
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{
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if (!__malloc_initialized)
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return;
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/* We do not acquire free_list_lock here because we completely
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reconstruct free_list in __malloc_fork_unlock_child. */
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__libc_lock_lock (list_lock);
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for (mstate ar_ptr = &main_arena;; )
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{
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__libc_lock_lock (ar_ptr->mutex);
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ar_ptr = ar_ptr->next;
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if (ar_ptr == &main_arena)
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break;
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}
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}
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void
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__malloc_fork_unlock_parent (void)
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{
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if (!__malloc_initialized)
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return;
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for (mstate ar_ptr = &main_arena;; )
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{
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__libc_lock_unlock (ar_ptr->mutex);
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ar_ptr = ar_ptr->next;
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if (ar_ptr == &main_arena)
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break;
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}
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__libc_lock_unlock (list_lock);
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}
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void
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__malloc_fork_unlock_child (void)
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{
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if (!__malloc_initialized)
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return;
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/* Push all arenas to the free list, except thread_arena, which is
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attached to the current thread. */
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__libc_lock_init (free_list_lock);
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if (thread_arena != NULL)
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thread_arena->attached_threads = 1;
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free_list = NULL;
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for (mstate ar_ptr = &main_arena;; )
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{
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__libc_lock_init (ar_ptr->mutex);
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if (ar_ptr != thread_arena)
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{
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/* This arena is no longer attached to any thread. */
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ar_ptr->attached_threads = 0;
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ar_ptr->next_free = free_list;
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free_list = ar_ptr;
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}
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ar_ptr = ar_ptr->next;
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if (ar_ptr == &main_arena)
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break;
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}
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__libc_lock_init (list_lock);
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}
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#if HAVE_TUNABLES
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# define TUNABLE_CALLBACK_FNDECL(__name, __type) \
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static inline int do_ ## __name (__type value); \
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static void \
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TUNABLE_CALLBACK (__name) (tunable_val_t *valp) \
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{ \
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__type value = (__type) (valp)->numval; \
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do_ ## __name (value); \
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}
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TUNABLE_CALLBACK_FNDECL (set_mmap_threshold, size_t)
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TUNABLE_CALLBACK_FNDECL (set_mmaps_max, int32_t)
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TUNABLE_CALLBACK_FNDECL (set_top_pad, size_t)
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TUNABLE_CALLBACK_FNDECL (set_perturb_byte, int32_t)
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TUNABLE_CALLBACK_FNDECL (set_trim_threshold, size_t)
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TUNABLE_CALLBACK_FNDECL (set_arena_max, size_t)
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TUNABLE_CALLBACK_FNDECL (set_arena_test, size_t)
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#if USE_TCACHE
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TUNABLE_CALLBACK_FNDECL (set_tcache_max, size_t)
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TUNABLE_CALLBACK_FNDECL (set_tcache_count, size_t)
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TUNABLE_CALLBACK_FNDECL (set_tcache_unsorted_limit, size_t)
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#endif
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TUNABLE_CALLBACK_FNDECL (set_mxfast, size_t)
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TUNABLE_CALLBACK_FNDECL (set_hugetlb, size_t)
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#else
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/* Initialization routine. */
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#include <string.h>
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extern char **_environ;
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static char *
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next_env_entry (char ***position)
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{
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char **current = *position;
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char *result = NULL;
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while (*current != NULL)
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{
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if (__builtin_expect ((*current)[0] == 'M', 0)
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&& (*current)[1] == 'A'
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&& (*current)[2] == 'L'
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&& (*current)[3] == 'L'
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&& (*current)[4] == 'O'
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&& (*current)[5] == 'C'
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&& (*current)[6] == '_')
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{
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result = &(*current)[7];
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/* Save current position for next visit. */
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*position = ++current;
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break;
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}
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++current;
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}
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return result;
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}
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#endif
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#ifdef SHARED
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extern struct dl_open_hook *_dl_open_hook;
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libc_hidden_proto (_dl_open_hook);
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#endif
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#if USE_TCACHE
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static void tcache_key_initialize (void);
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#endif
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static void
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ptmalloc_init (void)
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{
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if (__malloc_initialized)
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return;
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__malloc_initialized = true;
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#if USE_TCACHE
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tcache_key_initialize ();
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#endif
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#ifdef USE_MTAG
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if ((TUNABLE_GET_FULL (glibc, mem, tagging, int32_t, NULL) & 1) != 0)
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{
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/* If the tunable says that we should be using tagged memory
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and that morecore does not support tagged regions, then
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disable it. */
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if (__MTAG_SBRK_UNTAGGED)
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__always_fail_morecore = true;
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mtag_enabled = true;
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mtag_mmap_flags = __MTAG_MMAP_FLAGS;
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}
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#endif
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#if defined SHARED && IS_IN (libc)
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/* In case this libc copy is in a non-default namespace, never use
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brk. Likewise if dlopened from statically linked program. The
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generic sbrk implementation also enforces this, but it is not
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used on Hurd. */
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if (!__libc_initial)
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__always_fail_morecore = true;
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#endif
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thread_arena = &main_arena;
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malloc_init_state (&main_arena);
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#if HAVE_TUNABLES
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TUNABLE_GET (top_pad, size_t, TUNABLE_CALLBACK (set_top_pad));
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TUNABLE_GET (perturb, int32_t, TUNABLE_CALLBACK (set_perturb_byte));
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TUNABLE_GET (mmap_threshold, size_t, TUNABLE_CALLBACK (set_mmap_threshold));
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TUNABLE_GET (trim_threshold, size_t, TUNABLE_CALLBACK (set_trim_threshold));
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TUNABLE_GET (mmap_max, int32_t, TUNABLE_CALLBACK (set_mmaps_max));
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TUNABLE_GET (arena_max, size_t, TUNABLE_CALLBACK (set_arena_max));
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TUNABLE_GET (arena_test, size_t, TUNABLE_CALLBACK (set_arena_test));
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# if USE_TCACHE
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TUNABLE_GET (tcache_max, size_t, TUNABLE_CALLBACK (set_tcache_max));
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TUNABLE_GET (tcache_count, size_t, TUNABLE_CALLBACK (set_tcache_count));
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TUNABLE_GET (tcache_unsorted_limit, size_t,
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TUNABLE_CALLBACK (set_tcache_unsorted_limit));
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# endif
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TUNABLE_GET (mxfast, size_t, TUNABLE_CALLBACK (set_mxfast));
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TUNABLE_GET (hugetlb, size_t, TUNABLE_CALLBACK (set_hugetlb));
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if (mp_.hp_pagesize > 0)
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|
/* Force mmap for main arena instead of sbrk, so hugepages are explicitly
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|
used. */
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__always_fail_morecore = true;
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#else
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if (__glibc_likely (_environ != NULL))
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{
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char **runp = _environ;
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char *envline;
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while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
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0))
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{
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size_t len = strcspn (envline, "=");
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if (envline[len] != '=')
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/* This is a "MALLOC_" variable at the end of the string
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without a '=' character. Ignore it since otherwise we
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will access invalid memory below. */
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continue;
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|
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switch (len)
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{
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case 8:
|
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if (!__builtin_expect (__libc_enable_secure, 0))
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{
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if (memcmp (envline, "TOP_PAD_", 8) == 0)
|
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__libc_mallopt (M_TOP_PAD, atoi (&envline[9]));
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else if (memcmp (envline, "PERTURB_", 8) == 0)
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__libc_mallopt (M_PERTURB, atoi (&envline[9]));
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}
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break;
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case 9:
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if (!__builtin_expect (__libc_enable_secure, 0))
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{
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if (memcmp (envline, "MMAP_MAX_", 9) == 0)
|
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__libc_mallopt (M_MMAP_MAX, atoi (&envline[10]));
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else if (memcmp (envline, "ARENA_MAX", 9) == 0)
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__libc_mallopt (M_ARENA_MAX, atoi (&envline[10]));
|
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}
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break;
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case 10:
|
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if (!__builtin_expect (__libc_enable_secure, 0))
|
|
{
|
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if (memcmp (envline, "ARENA_TEST", 10) == 0)
|
|
__libc_mallopt (M_ARENA_TEST, atoi (&envline[11]));
|
|
}
|
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break;
|
|
case 15:
|
|
if (!__builtin_expect (__libc_enable_secure, 0))
|
|
{
|
|
if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
|
|
__libc_mallopt (M_TRIM_THRESHOLD, atoi (&envline[16]));
|
|
else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
|
|
__libc_mallopt (M_MMAP_THRESHOLD, atoi (&envline[16]));
|
|
}
|
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break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/* Managing heaps and arenas (for concurrent threads) */
|
|
|
|
#if MALLOC_DEBUG > 1
|
|
|
|
/* Print the complete contents of a single heap to stderr. */
|
|
|
|
static void
|
|
dump_heap (heap_info *heap)
|
|
{
|
|
char *ptr;
|
|
mchunkptr p;
|
|
|
|
fprintf (stderr, "Heap %p, size %10lx:\n", heap, (long) heap->size);
|
|
ptr = (heap->ar_ptr != (mstate) (heap + 1)) ?
|
|
(char *) (heap + 1) : (char *) (heap + 1) + sizeof (struct malloc_state);
|
|
p = (mchunkptr) (((unsigned long) ptr + MALLOC_ALIGN_MASK) &
|
|
~MALLOC_ALIGN_MASK);
|
|
for (;; )
|
|
{
|
|
fprintf (stderr, "chunk %p size %10lx", p, (long) chunksize_nomask(p));
|
|
if (p == top (heap->ar_ptr))
|
|
{
|
|
fprintf (stderr, " (top)\n");
|
|
break;
|
|
}
|
|
else if (chunksize_nomask(p) == (0 | PREV_INUSE))
|
|
{
|
|
fprintf (stderr, " (fence)\n");
|
|
break;
|
|
}
|
|
fprintf (stderr, "\n");
|
|
p = next_chunk (p);
|
|
}
|
|
}
|
|
#endif /* MALLOC_DEBUG > 1 */
|
|
|
|
/* If consecutive mmap (0, HEAP_MAX_SIZE << 1, ...) calls return decreasing
|
|
addresses as opposed to increasing, new_heap would badly fragment the
|
|
address space. In that case remember the second HEAP_MAX_SIZE part
|
|
aligned to HEAP_MAX_SIZE from last mmap (0, HEAP_MAX_SIZE << 1, ...)
|
|
call (if it is already aligned) and try to reuse it next time. We need
|
|
no locking for it, as kernel ensures the atomicity for us - worst case
|
|
we'll call mmap (addr, HEAP_MAX_SIZE, ...) for some value of addr in
|
|
multiple threads, but only one will succeed. */
|
|
static char *aligned_heap_area;
|
|
|
|
/* Create a new heap. size is automatically rounded up to a multiple
|
|
of the page size. */
|
|
|
|
static heap_info *
|
|
alloc_new_heap (size_t size, size_t top_pad, size_t pagesize,
|
|
int mmap_flags)
|
|
{
|
|
char *p1, *p2;
|
|
unsigned long ul;
|
|
heap_info *h;
|
|
size_t min_size = heap_min_size ();
|
|
size_t max_size = heap_max_size ();
|
|
|
|
if (size + top_pad < min_size)
|
|
size = min_size;
|
|
else if (size + top_pad <= max_size)
|
|
size += top_pad;
|
|
else if (size > max_size)
|
|
return 0;
|
|
else
|
|
size = max_size;
|
|
size = ALIGN_UP (size, pagesize);
|
|
|
|
/* A memory region aligned to a multiple of max_size is needed.
|
|
No swap space needs to be reserved for the following large
|
|
mapping (on Linux, this is the case for all non-writable mappings
|
|
anyway). */
|
|
p2 = MAP_FAILED;
|
|
if (aligned_heap_area)
|
|
{
|
|
p2 = (char *) MMAP (aligned_heap_area, max_size, PROT_NONE, mmap_flags);
|
|
aligned_heap_area = NULL;
|
|
if (p2 != MAP_FAILED && ((unsigned long) p2 & (max_size - 1)))
|
|
{
|
|
__munmap (p2, max_size);
|
|
p2 = MAP_FAILED;
|
|
}
|
|
}
|
|
if (p2 == MAP_FAILED)
|
|
{
|
|
p1 = (char *) MMAP (0, max_size << 1, PROT_NONE, mmap_flags);
|
|
if (p1 != MAP_FAILED)
|
|
{
|
|
p2 = (char *) (((unsigned long) p1 + (max_size - 1))
|
|
& ~(max_size - 1));
|
|
ul = p2 - p1;
|
|
if (ul)
|
|
__munmap (p1, ul);
|
|
else
|
|
aligned_heap_area = p2 + max_size;
|
|
__munmap (p2 + max_size, max_size - ul);
|
|
}
|
|
else
|
|
{
|
|
/* Try to take the chance that an allocation of only max_size
|
|
is already aligned. */
|
|
p2 = (char *) MMAP (0, max_size, PROT_NONE, mmap_flags);
|
|
if (p2 == MAP_FAILED)
|
|
return 0;
|
|
|
|
if ((unsigned long) p2 & (max_size - 1))
|
|
{
|
|
__munmap (p2, max_size);
|
|
return 0;
|
|
}
|
|
}
|
|
}
|
|
if (__mprotect (p2, size, mtag_mmap_flags | PROT_READ | PROT_WRITE) != 0)
|
|
{
|
|
__munmap (p2, max_size);
|
|
return 0;
|
|
}
|
|
|
|
madvise_thp (p2, size);
|
|
|
|
h = (heap_info *) p2;
|
|
h->size = size;
|
|
h->mprotect_size = size;
|
|
h->pagesize = pagesize;
|
|
LIBC_PROBE (memory_heap_new, 2, h, h->size);
|
|
return h;
|
|
}
|
|
|
|
static heap_info *
|
|
new_heap (size_t size, size_t top_pad)
|
|
{
|
|
#if HAVE_TUNABLES
|
|
if (__glibc_unlikely (mp_.hp_pagesize != 0))
|
|
{
|
|
/* MAP_NORESERVE is not used for huge pages because some kernel may
|
|
not reserve the mmap region and a subsequent access may trigger
|
|
a SIGBUS if there is no free pages in the pool. */
|
|
heap_info *h = alloc_new_heap (size, top_pad, mp_.hp_pagesize,
|
|
mp_.hp_flags);
|
|
if (h != NULL)
|
|
return h;
|
|
}
|
|
#endif
|
|
return alloc_new_heap (size, top_pad, GLRO (dl_pagesize), MAP_NORESERVE);
|
|
}
|
|
|
|
/* Grow a heap. size is automatically rounded up to a
|
|
multiple of the page size. */
|
|
|
|
static int
|
|
grow_heap (heap_info *h, long diff)
|
|
{
|
|
size_t pagesize = h->pagesize;
|
|
size_t max_size = heap_max_size ();
|
|
long new_size;
|
|
|
|
diff = ALIGN_UP (diff, pagesize);
|
|
new_size = (long) h->size + diff;
|
|
if ((unsigned long) new_size > (unsigned long) max_size)
|
|
return -1;
|
|
|
|
if ((unsigned long) new_size > h->mprotect_size)
|
|
{
|
|
if (__mprotect ((char *) h + h->mprotect_size,
|
|
(unsigned long) new_size - h->mprotect_size,
|
|
mtag_mmap_flags | PROT_READ | PROT_WRITE) != 0)
|
|
return -2;
|
|
|
|
h->mprotect_size = new_size;
|
|
}
|
|
|
|
h->size = new_size;
|
|
LIBC_PROBE (memory_heap_more, 2, h, h->size);
|
|
return 0;
|
|
}
|
|
|
|
/* Shrink a heap. */
|
|
|
|
static int
|
|
shrink_heap (heap_info *h, long diff)
|
|
{
|
|
long new_size;
|
|
|
|
new_size = (long) h->size - diff;
|
|
if (new_size < (long) sizeof (*h))
|
|
return -1;
|
|
|
|
/* Try to re-map the extra heap space freshly to save memory, and make it
|
|
inaccessible. See malloc-sysdep.h to know when this is true. */
|
|
if (__glibc_unlikely (check_may_shrink_heap ()))
|
|
{
|
|
if ((char *) MMAP ((char *) h + new_size, diff, PROT_NONE,
|
|
MAP_FIXED) == (char *) MAP_FAILED)
|
|
return -2;
|
|
|
|
h->mprotect_size = new_size;
|
|
}
|
|
else
|
|
__madvise ((char *) h + new_size, diff, MADV_DONTNEED);
|
|
/*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
|
|
|
|
h->size = new_size;
|
|
LIBC_PROBE (memory_heap_less, 2, h, h->size);
|
|
return 0;
|
|
}
|
|
|
|
/* Delete a heap. */
|
|
|
|
static int
|
|
heap_trim (heap_info *heap, size_t pad)
|
|
{
|
|
mstate ar_ptr = heap->ar_ptr;
|
|
mchunkptr top_chunk = top (ar_ptr), p;
|
|
heap_info *prev_heap;
|
|
long new_size, top_size, top_area, extra, prev_size, misalign;
|
|
size_t max_size = heap_max_size ();
|
|
|
|
/* Can this heap go away completely? */
|
|
while (top_chunk == chunk_at_offset (heap, sizeof (*heap)))
|
|
{
|
|
prev_heap = heap->prev;
|
|
prev_size = prev_heap->size - (MINSIZE - 2 * SIZE_SZ);
|
|
p = chunk_at_offset (prev_heap, prev_size);
|
|
/* fencepost must be properly aligned. */
|
|
misalign = ((long) p) & MALLOC_ALIGN_MASK;
|
|
p = chunk_at_offset (prev_heap, prev_size - misalign);
|
|
assert (chunksize_nomask (p) == (0 | PREV_INUSE)); /* must be fencepost */
|
|
p = prev_chunk (p);
|
|
new_size = chunksize (p) + (MINSIZE - 2 * SIZE_SZ) + misalign;
|
|
assert (new_size > 0 && new_size < (long) (2 * MINSIZE));
|
|
if (!prev_inuse (p))
|
|
new_size += prev_size (p);
|
|
assert (new_size > 0 && new_size < max_size);
|
|
if (new_size + (max_size - prev_heap->size) < pad + MINSIZE
|
|
+ heap->pagesize)
|
|
break;
|
|
ar_ptr->system_mem -= heap->size;
|
|
LIBC_PROBE (memory_heap_free, 2, heap, heap->size);
|
|
if ((char *) heap + max_size == aligned_heap_area)
|
|
aligned_heap_area = NULL;
|
|
__munmap (heap, max_size);
|
|
heap = prev_heap;
|
|
if (!prev_inuse (p)) /* consolidate backward */
|
|
{
|
|
p = prev_chunk (p);
|
|
unlink_chunk (ar_ptr, p);
|
|
}
|
|
assert (((unsigned long) ((char *) p + new_size) & (heap->pagesize - 1))
|
|
== 0);
|
|
assert (((char *) p + new_size) == ((char *) heap + heap->size));
|
|
top (ar_ptr) = top_chunk = p;
|
|
set_head (top_chunk, new_size | PREV_INUSE);
|
|
/*check_chunk(ar_ptr, top_chunk);*/
|
|
}
|
|
|
|
/* Uses similar logic for per-thread arenas as the main arena with systrim
|
|
and _int_free by preserving the top pad and rounding down to the nearest
|
|
page. */
|
|
top_size = chunksize (top_chunk);
|
|
if ((unsigned long)(top_size) <
|
|
(unsigned long)(mp_.trim_threshold))
|
|
return 0;
|
|
|
|
top_area = top_size - MINSIZE - 1;
|
|
if (top_area < 0 || (size_t) top_area <= pad)
|
|
return 0;
|
|
|
|
/* Release in pagesize units and round down to the nearest page. */
|
|
extra = ALIGN_DOWN(top_area - pad, heap->pagesize);
|
|
if (extra == 0)
|
|
return 0;
|
|
|
|
/* Try to shrink. */
|
|
if (shrink_heap (heap, extra) != 0)
|
|
return 0;
|
|
|
|
ar_ptr->system_mem -= extra;
|
|
|
|
/* Success. Adjust top accordingly. */
|
|
set_head (top_chunk, (top_size - extra) | PREV_INUSE);
|
|
/*check_chunk(ar_ptr, top_chunk);*/
|
|
return 1;
|
|
}
|
|
|
|
/* Create a new arena with initial size "size". */
|
|
|
|
#if IS_IN (libc)
|
|
/* If REPLACED_ARENA is not NULL, detach it from this thread. Must be
|
|
called while free_list_lock is held. */
|
|
static void
|
|
detach_arena (mstate replaced_arena)
|
|
{
|
|
if (replaced_arena != NULL)
|
|
{
|
|
assert (replaced_arena->attached_threads > 0);
|
|
/* The current implementation only detaches from main_arena in
|
|
case of allocation failure. This means that it is likely not
|
|
beneficial to put the arena on free_list even if the
|
|
reference count reaches zero. */
|
|
--replaced_arena->attached_threads;
|
|
}
|
|
}
|
|
|
|
static mstate
|
|
_int_new_arena (size_t size)
|
|
{
|
|
mstate a;
|
|
heap_info *h;
|
|
char *ptr;
|
|
unsigned long misalign;
|
|
|
|
h = new_heap (size + (sizeof (*h) + sizeof (*a) + MALLOC_ALIGNMENT),
|
|
mp_.top_pad);
|
|
if (!h)
|
|
{
|
|
/* Maybe size is too large to fit in a single heap. So, just try
|
|
to create a minimally-sized arena and let _int_malloc() attempt
|
|
to deal with the large request via mmap_chunk(). */
|
|
h = new_heap (sizeof (*h) + sizeof (*a) + MALLOC_ALIGNMENT, mp_.top_pad);
|
|
if (!h)
|
|
return 0;
|
|
}
|
|
a = h->ar_ptr = (mstate) (h + 1);
|
|
malloc_init_state (a);
|
|
a->attached_threads = 1;
|
|
/*a->next = NULL;*/
|
|
a->system_mem = a->max_system_mem = h->size;
|
|
|
|
/* Set up the top chunk, with proper alignment. */
|
|
ptr = (char *) (a + 1);
|
|
misalign = (unsigned long) chunk2mem (ptr) & MALLOC_ALIGN_MASK;
|
|
if (misalign > 0)
|
|
ptr += MALLOC_ALIGNMENT - misalign;
|
|
top (a) = (mchunkptr) ptr;
|
|
set_head (top (a), (((char *) h + h->size) - ptr) | PREV_INUSE);
|
|
|
|
LIBC_PROBE (memory_arena_new, 2, a, size);
|
|
mstate replaced_arena = thread_arena;
|
|
thread_arena = a;
|
|
__libc_lock_init (a->mutex);
|
|
|
|
__libc_lock_lock (list_lock);
|
|
|
|
/* Add the new arena to the global list. */
|
|
a->next = main_arena.next;
|
|
/* FIXME: The barrier is an attempt to synchronize with read access
|
|
in reused_arena, which does not acquire list_lock while
|
|
traversing the list. */
|
|
atomic_write_barrier ();
|
|
main_arena.next = a;
|
|
|
|
__libc_lock_unlock (list_lock);
|
|
|
|
__libc_lock_lock (free_list_lock);
|
|
detach_arena (replaced_arena);
|
|
__libc_lock_unlock (free_list_lock);
|
|
|
|
/* Lock this arena. NB: Another thread may have been attached to
|
|
this arena because the arena is now accessible from the
|
|
main_arena.next list and could have been picked by reused_arena.
|
|
This can only happen for the last arena created (before the arena
|
|
limit is reached). At this point, some arena has to be attached
|
|
to two threads. We could acquire the arena lock before list_lock
|
|
to make it less likely that reused_arena picks this new arena,
|
|
but this could result in a deadlock with
|
|
__malloc_fork_lock_parent. */
|
|
|
|
__libc_lock_lock (a->mutex);
|
|
|
|
return a;
|
|
}
|
|
|
|
|
|
/* Remove an arena from free_list. */
|
|
static mstate
|
|
get_free_list (void)
|
|
{
|
|
mstate replaced_arena = thread_arena;
|
|
mstate result = free_list;
|
|
if (result != NULL)
|
|
{
|
|
__libc_lock_lock (free_list_lock);
|
|
result = free_list;
|
|
if (result != NULL)
|
|
{
|
|
free_list = result->next_free;
|
|
|
|
/* The arena will be attached to this thread. */
|
|
assert (result->attached_threads == 0);
|
|
result->attached_threads = 1;
|
|
|
|
detach_arena (replaced_arena);
|
|
}
|
|
__libc_lock_unlock (free_list_lock);
|
|
|
|
if (result != NULL)
|
|
{
|
|
LIBC_PROBE (memory_arena_reuse_free_list, 1, result);
|
|
__libc_lock_lock (result->mutex);
|
|
thread_arena = result;
|
|
}
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
/* Remove the arena from the free list (if it is present).
|
|
free_list_lock must have been acquired by the caller. */
|
|
static void
|
|
remove_from_free_list (mstate arena)
|
|
{
|
|
mstate *previous = &free_list;
|
|
for (mstate p = free_list; p != NULL; p = p->next_free)
|
|
{
|
|
assert (p->attached_threads == 0);
|
|
if (p == arena)
|
|
{
|
|
/* Remove the requested arena from the list. */
|
|
*previous = p->next_free;
|
|
break;
|
|
}
|
|
else
|
|
previous = &p->next_free;
|
|
}
|
|
}
|
|
|
|
/* Lock and return an arena that can be reused for memory allocation.
|
|
Avoid AVOID_ARENA as we have already failed to allocate memory in
|
|
it and it is currently locked. */
|
|
static mstate
|
|
reused_arena (mstate avoid_arena)
|
|
{
|
|
mstate result;
|
|
/* FIXME: Access to next_to_use suffers from data races. */
|
|
static mstate next_to_use;
|
|
if (next_to_use == NULL)
|
|
next_to_use = &main_arena;
|
|
|
|
/* Iterate over all arenas (including those linked from
|
|
free_list). */
|
|
result = next_to_use;
|
|
do
|
|
{
|
|
if (!__libc_lock_trylock (result->mutex))
|
|
goto out;
|
|
|
|
/* FIXME: This is a data race, see _int_new_arena. */
|
|
result = result->next;
|
|
}
|
|
while (result != next_to_use);
|
|
|
|
/* Avoid AVOID_ARENA as we have already failed to allocate memory
|
|
in that arena and it is currently locked. */
|
|
if (result == avoid_arena)
|
|
result = result->next;
|
|
|
|
/* No arena available without contention. Wait for the next in line. */
|
|
LIBC_PROBE (memory_arena_reuse_wait, 3, &result->mutex, result, avoid_arena);
|
|
__libc_lock_lock (result->mutex);
|
|
|
|
out:
|
|
/* Attach the arena to the current thread. */
|
|
{
|
|
/* Update the arena thread attachment counters. */
|
|
mstate replaced_arena = thread_arena;
|
|
__libc_lock_lock (free_list_lock);
|
|
detach_arena (replaced_arena);
|
|
|
|
/* We may have picked up an arena on the free list. We need to
|
|
preserve the invariant that no arena on the free list has a
|
|
positive attached_threads counter (otherwise,
|
|
arena_thread_freeres cannot use the counter to determine if the
|
|
arena needs to be put on the free list). We unconditionally
|
|
remove the selected arena from the free list. The caller of
|
|
reused_arena checked the free list and observed it to be empty,
|
|
so the list is very short. */
|
|
remove_from_free_list (result);
|
|
|
|
++result->attached_threads;
|
|
|
|
__libc_lock_unlock (free_list_lock);
|
|
}
|
|
|
|
LIBC_PROBE (memory_arena_reuse, 2, result, avoid_arena);
|
|
thread_arena = result;
|
|
next_to_use = result->next;
|
|
|
|
return result;
|
|
}
|
|
|
|
static mstate
|
|
arena_get2 (size_t size, mstate avoid_arena)
|
|
{
|
|
mstate a;
|
|
|
|
static size_t narenas_limit;
|
|
|
|
a = get_free_list ();
|
|
if (a == NULL)
|
|
{
|
|
/* Nothing immediately available, so generate a new arena. */
|
|
if (narenas_limit == 0)
|
|
{
|
|
if (mp_.arena_max != 0)
|
|
narenas_limit = mp_.arena_max;
|
|
else if (narenas > mp_.arena_test)
|
|
{
|
|
int n = __get_nprocs_sched ();
|
|
|
|
if (n >= 1)
|
|
narenas_limit = NARENAS_FROM_NCORES (n);
|
|
else
|
|
/* We have no information about the system. Assume two
|
|
cores. */
|
|
narenas_limit = NARENAS_FROM_NCORES (2);
|
|
}
|
|
}
|
|
repeat:;
|
|
size_t n = narenas;
|
|
/* NB: the following depends on the fact that (size_t)0 - 1 is a
|
|
very large number and that the underflow is OK. If arena_max
|
|
is set the value of arena_test is irrelevant. If arena_test
|
|
is set but narenas is not yet larger or equal to arena_test
|
|
narenas_limit is 0. There is no possibility for narenas to
|
|
be too big for the test to always fail since there is not
|
|
enough address space to create that many arenas. */
|
|
if (__glibc_unlikely (n <= narenas_limit - 1))
|
|
{
|
|
if (catomic_compare_and_exchange_bool_acq (&narenas, n + 1, n))
|
|
goto repeat;
|
|
a = _int_new_arena (size);
|
|
if (__glibc_unlikely (a == NULL))
|
|
catomic_decrement (&narenas);
|
|
}
|
|
else
|
|
a = reused_arena (avoid_arena);
|
|
}
|
|
return a;
|
|
}
|
|
|
|
/* If we don't have the main arena, then maybe the failure is due to running
|
|
out of mmapped areas, so we can try allocating on the main arena.
|
|
Otherwise, it is likely that sbrk() has failed and there is still a chance
|
|
to mmap(), so try one of the other arenas. */
|
|
static mstate
|
|
arena_get_retry (mstate ar_ptr, size_t bytes)
|
|
{
|
|
LIBC_PROBE (memory_arena_retry, 2, bytes, ar_ptr);
|
|
if (ar_ptr != &main_arena)
|
|
{
|
|
__libc_lock_unlock (ar_ptr->mutex);
|
|
ar_ptr = &main_arena;
|
|
__libc_lock_lock (ar_ptr->mutex);
|
|
}
|
|
else
|
|
{
|
|
__libc_lock_unlock (ar_ptr->mutex);
|
|
ar_ptr = arena_get2 (bytes, ar_ptr);
|
|
}
|
|
|
|
return ar_ptr;
|
|
}
|
|
#endif
|
|
|
|
void
|
|
__malloc_arena_thread_freeres (void)
|
|
{
|
|
/* Shut down the thread cache first. This could deallocate data for
|
|
the thread arena, so do this before we put the arena on the free
|
|
list. */
|
|
tcache_thread_shutdown ();
|
|
|
|
mstate a = thread_arena;
|
|
thread_arena = NULL;
|
|
|
|
if (a != NULL)
|
|
{
|
|
__libc_lock_lock (free_list_lock);
|
|
/* If this was the last attached thread for this arena, put the
|
|
arena on the free list. */
|
|
assert (a->attached_threads > 0);
|
|
if (--a->attached_threads == 0)
|
|
{
|
|
a->next_free = free_list;
|
|
free_list = a;
|
|
}
|
|
__libc_lock_unlock (free_list_lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Local variables:
|
|
* c-basic-offset: 2
|
|
* End:
|
|
*/
|