a95018ee81
This adds support for expanding huge allocations in-place by requesting memory at a specific address from the chunk allocator. It's currently only implemented for the chunk recycling path, although in theory it could also be done by optimistically allocating new chunks. On Linux, it could attempt an in-place mremap. However, that won't work in practice since the heap is grown downwards and memory is not unmapped (in a normal build, at least). Repeated vector reallocation micro-benchmark: #include <string.h> #include <stdlib.h> int main(void) { for (size_t i = 0; i < 100; i++) { void *ptr = NULL; size_t old_size = 0; for (size_t size = 4; size < (1 << 30); size *= 2) { ptr = realloc(ptr, size); if (!ptr) return 1; memset(ptr + old_size, 0xff, size - old_size); old_size = size; } free(ptr); } } The glibc allocator fails to do any in-place reallocations on this benchmark once it passes the M_MMAP_THRESHOLD (default 128k) but it elides the cost of copies via mremap, which is currently not something that jemalloc can use. With this improvement, jemalloc still fails to do any in-place huge reallocations for the first outer loop, but then succeeds 100% of the time for the remaining 99 iterations. The time spent doing allocations and copies drops down to under 5%, with nearly all of it spent doing purging + faulting (when huge pages are disabled) and the array memset. An improved mremap API (MREMAP_RETAIN - #138) would be far more general but this is a portable optimization and would still be useful on Linux for xallocx. Numbers with transparent huge pages enabled: glibc (copies elided via MREMAP_MAYMOVE): 8.471s jemalloc: 17.816s jemalloc + no-op madvise: 13.236s jemalloc + this commit: 6.787s jemalloc + this commit + no-op madvise: 6.144s Numbers with transparent huge pages disabled: glibc (copies elided via MREMAP_MAYMOVE): 15.403s jemalloc: 39.456s jemalloc + no-op madvise: 12.768s jemalloc + this commit: 15.534s jemalloc + this commit + no-op madvise: 6.354s Closes #137
371 lines
8.0 KiB
C
371 lines
8.0 KiB
C
#define JEMALLOC_HUGE_C_
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#include "jemalloc/internal/jemalloc_internal.h"
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/******************************************************************************/
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/* Data. */
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/* Protects chunk-related data structures. */
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static malloc_mutex_t huge_mtx;
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/******************************************************************************/
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/* Tree of chunks that are stand-alone huge allocations. */
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static extent_tree_t huge;
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void *
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huge_malloc(tsd_t *tsd, arena_t *arena, size_t size, bool zero)
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{
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return (huge_palloc(tsd, arena, size, chunksize, zero));
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}
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void *
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huge_palloc(tsd_t *tsd, arena_t *arena, size_t size, size_t alignment,
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bool zero)
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{
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void *ret;
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size_t csize;
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extent_node_t *node;
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bool is_zeroed;
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/* Allocate one or more contiguous chunks for this request. */
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csize = CHUNK_CEILING(size);
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if (csize == 0) {
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/* size is large enough to cause size_t wrap-around. */
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return (NULL);
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}
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/* Allocate an extent node with which to track the chunk. */
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node = base_node_alloc();
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if (node == NULL)
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return (NULL);
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/*
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* Copy zero into is_zeroed and pass the copy to chunk_alloc(), so that
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* it is possible to make correct junk/zero fill decisions below.
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*/
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is_zeroed = zero;
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arena = choose_arena(tsd, arena);
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ret = arena_chunk_alloc_huge(arena, NULL, csize, alignment, &is_zeroed);
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if (ret == NULL) {
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base_node_dalloc(node);
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return (NULL);
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}
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/* Insert node into huge. */
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node->addr = ret;
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node->size = csize;
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node->arena = arena;
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malloc_mutex_lock(&huge_mtx);
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extent_tree_ad_insert(&huge, node);
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malloc_mutex_unlock(&huge_mtx);
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if (config_fill && !zero) {
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if (unlikely(opt_junk))
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memset(ret, 0xa5, csize);
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else if (unlikely(opt_zero) && !is_zeroed)
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memset(ret, 0, csize);
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}
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return (ret);
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}
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#ifdef JEMALLOC_JET
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#undef huge_dalloc_junk
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#define huge_dalloc_junk JEMALLOC_N(huge_dalloc_junk_impl)
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#endif
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static void
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huge_dalloc_junk(void *ptr, size_t usize)
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{
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if (config_fill && have_dss && unlikely(opt_junk)) {
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/*
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* Only bother junk filling if the chunk isn't about to be
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* unmapped.
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*/
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if (!config_munmap || (have_dss && chunk_in_dss(ptr)))
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memset(ptr, 0x5a, usize);
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}
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}
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#ifdef JEMALLOC_JET
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#undef huge_dalloc_junk
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#define huge_dalloc_junk JEMALLOC_N(huge_dalloc_junk)
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huge_dalloc_junk_t *huge_dalloc_junk = JEMALLOC_N(huge_dalloc_junk_impl);
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#endif
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static bool
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huge_ralloc_no_move_expand(void *ptr, size_t oldsize, size_t size, bool zero) {
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size_t csize;
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void *expand_addr;
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size_t expand_size;
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extent_node_t *node, key;
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arena_t *arena;
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bool is_zeroed;
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void *ret;
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csize = CHUNK_CEILING(size);
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if (csize == 0) {
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/* size is large enough to cause size_t wrap-around. */
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return (true);
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}
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expand_addr = ptr + oldsize;
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expand_size = csize - oldsize;
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malloc_mutex_lock(&huge_mtx);
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key.addr = ptr;
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node = extent_tree_ad_search(&huge, &key);
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assert(node != NULL);
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assert(node->addr == ptr);
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/* Find the current arena. */
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arena = node->arena;
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malloc_mutex_unlock(&huge_mtx);
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/*
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* Copy zero into is_zeroed and pass the copy to chunk_alloc(), so that
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* it is possible to make correct junk/zero fill decisions below.
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*/
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is_zeroed = zero;
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ret = arena_chunk_alloc_huge(arena, expand_addr, expand_size, chunksize,
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&is_zeroed);
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if (ret == NULL)
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return (true);
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assert(ret == expand_addr);
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malloc_mutex_lock(&huge_mtx);
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/* Update the size of the huge allocation. */
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node->size = csize;
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malloc_mutex_unlock(&huge_mtx);
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if (config_fill && !zero) {
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if (unlikely(opt_junk))
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memset(expand_addr, 0xa5, expand_size);
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else if (unlikely(opt_zero) && !is_zeroed)
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memset(expand_addr, 0, expand_size);
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}
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return (false);
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}
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bool
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huge_ralloc_no_move(void *ptr, size_t oldsize, size_t size, size_t extra,
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bool zero)
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{
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/* Both allocations must be huge to avoid a move. */
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if (oldsize <= arena_maxclass)
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return (true);
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assert(CHUNK_CEILING(oldsize) == oldsize);
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/*
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* Avoid moving the allocation if the size class can be left the same.
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*/
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if (CHUNK_CEILING(oldsize) >= CHUNK_CEILING(size)
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&& CHUNK_CEILING(oldsize) <= CHUNK_CEILING(size+extra)) {
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return (false);
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}
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/* Overflow. */
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if (CHUNK_CEILING(size) == 0)
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return (true);
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/* Shrink the allocation in-place. */
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if (CHUNK_CEILING(oldsize) > CHUNK_CEILING(size)) {
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extent_node_t *node, key;
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void *excess_addr;
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size_t excess_size;
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malloc_mutex_lock(&huge_mtx);
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key.addr = ptr;
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node = extent_tree_ad_search(&huge, &key);
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assert(node != NULL);
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assert(node->addr == ptr);
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/* Update the size of the huge allocation. */
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node->size = CHUNK_CEILING(size);
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malloc_mutex_unlock(&huge_mtx);
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excess_addr = node->addr + CHUNK_CEILING(size);
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excess_size = CHUNK_CEILING(oldsize) - CHUNK_CEILING(size);
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/* Zap the excess chunks. */
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huge_dalloc_junk(excess_addr, excess_size);
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arena_chunk_dalloc_huge(node->arena, excess_addr, excess_size);
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return (false);
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}
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/* Attempt to expand the allocation in-place. */
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if (huge_ralloc_no_move_expand(ptr, oldsize, size + extra, zero)) {
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if (extra == 0)
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return (true);
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/* Try again, this time without extra. */
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return (huge_ralloc_no_move_expand(ptr, oldsize, size, zero));
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}
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return (false);
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}
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void *
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huge_ralloc(tsd_t *tsd, arena_t *arena, void *ptr, size_t oldsize, size_t size,
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size_t extra, size_t alignment, bool zero, bool try_tcache_dalloc)
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{
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void *ret;
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size_t copysize;
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/* Try to avoid moving the allocation. */
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if (!huge_ralloc_no_move(ptr, oldsize, size, extra, zero))
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return (ptr);
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/*
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* size and oldsize are different enough that we need to use a
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* different size class. In that case, fall back to allocating new
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* space and copying.
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*/
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if (alignment > chunksize)
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ret = huge_palloc(tsd, arena, size + extra, alignment, zero);
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else
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ret = huge_malloc(tsd, arena, size + extra, zero);
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if (ret == NULL) {
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if (extra == 0)
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return (NULL);
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/* Try again, this time without extra. */
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if (alignment > chunksize)
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ret = huge_palloc(tsd, arena, size, alignment, zero);
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else
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ret = huge_malloc(tsd, arena, size, zero);
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if (ret == NULL)
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return (NULL);
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}
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/*
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* Copy at most size bytes (not size+extra), since the caller has no
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* expectation that the extra bytes will be reliably preserved.
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*/
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copysize = (size < oldsize) ? size : oldsize;
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memcpy(ret, ptr, copysize);
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iqalloc(tsd, ptr, try_tcache_dalloc);
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return (ret);
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}
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void
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huge_dalloc(void *ptr)
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{
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extent_node_t *node, key;
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malloc_mutex_lock(&huge_mtx);
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/* Extract from tree of huge allocations. */
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key.addr = ptr;
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node = extent_tree_ad_search(&huge, &key);
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assert(node != NULL);
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assert(node->addr == ptr);
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extent_tree_ad_remove(&huge, node);
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malloc_mutex_unlock(&huge_mtx);
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huge_dalloc_junk(node->addr, node->size);
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arena_chunk_dalloc_huge(node->arena, node->addr, node->size);
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base_node_dalloc(node);
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}
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size_t
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huge_salloc(const void *ptr)
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{
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size_t ret;
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extent_node_t *node, key;
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malloc_mutex_lock(&huge_mtx);
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/* Extract from tree of huge allocations. */
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key.addr = __DECONST(void *, ptr);
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node = extent_tree_ad_search(&huge, &key);
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assert(node != NULL);
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ret = node->size;
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malloc_mutex_unlock(&huge_mtx);
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return (ret);
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}
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prof_tctx_t *
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huge_prof_tctx_get(const void *ptr)
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{
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prof_tctx_t *ret;
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extent_node_t *node, key;
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malloc_mutex_lock(&huge_mtx);
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/* Extract from tree of huge allocations. */
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key.addr = __DECONST(void *, ptr);
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node = extent_tree_ad_search(&huge, &key);
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assert(node != NULL);
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ret = node->prof_tctx;
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malloc_mutex_unlock(&huge_mtx);
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return (ret);
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}
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void
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huge_prof_tctx_set(const void *ptr, prof_tctx_t *tctx)
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{
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extent_node_t *node, key;
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malloc_mutex_lock(&huge_mtx);
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/* Extract from tree of huge allocations. */
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key.addr = __DECONST(void *, ptr);
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node = extent_tree_ad_search(&huge, &key);
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assert(node != NULL);
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node->prof_tctx = tctx;
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malloc_mutex_unlock(&huge_mtx);
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}
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bool
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huge_boot(void)
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{
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/* Initialize chunks data. */
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if (malloc_mutex_init(&huge_mtx))
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return (true);
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extent_tree_ad_new(&huge);
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return (false);
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}
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void
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huge_prefork(void)
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{
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malloc_mutex_prefork(&huge_mtx);
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}
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void
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huge_postfork_parent(void)
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{
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malloc_mutex_postfork_parent(&huge_mtx);
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}
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void
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huge_postfork_child(void)
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{
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malloc_mutex_postfork_child(&huge_mtx);
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}
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