project-base/server-skynet-source-3rd-jemalloc
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Don't dereference chunk->arena in free() hot path

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When you call free() we load chunk->arena even though that
data isn't used on the tcache hot path.

In profiling some FB applications, I found that ~30% of the
dTLB misses in the free() function come from this line. With
4 MB chunks, the arena_chunk_t->map is ~ 32 KB (1024 pages
in the chunk, 4 8 byte pointers in arena_chunk_map_t). This
means there's only a 1/8 chance of the page containing
chunk->arena also comtaining the map bits.
This commit is contained in:
Ben Maurer 2014-04-05 15:59:08 -07:00
parent 46c0af68bd
commit be8e59f5a6
3 changed files with 6 additions and 9 deletions
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11
include/jemalloc/internal/arena.h
View File

@ -495,8 +495,7 @@ prof_ctx_t *arena_prof_ctx_get(const void *ptr);
void arena_prof_ctx_set(const void *ptr, size_t usize, prof_ctx_t *ctx);
void *arena_malloc(arena_t *arena, size_t size, bool zero, bool try_tcache);
size_t arena_salloc(const void *ptr, bool demote);
void arena_dalloc(arena_t *arena, arena_chunk_t *chunk, void *ptr,
bool try_tcache);
void arena_dalloc(arena_chunk_t *chunk, void *ptr, bool try_tcache);
#endif
#if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_ARENA_C_))
@ -1022,13 +1021,11 @@ arena_salloc(const void *ptr, bool demote)
}
JEMALLOC_ALWAYS_INLINE void
arena_dalloc(arena_t *arena, arena_chunk_t *chunk, void *ptr, bool try_tcache)
arena_dalloc(arena_chunk_t *chunk, void *ptr, bool try_tcache)
{
size_t pageind, mapbits;
tcache_t *tcache;
assert(arena != NULL);
assert(chunk->arena == arena);
assert(ptr != NULL);
assert(CHUNK_ADDR2BASE(ptr) != ptr);
@ -1043,7 +1040,7 @@ arena_dalloc(arena_t *arena, arena_chunk_t *chunk, void *ptr, bool try_tcache)
binind = arena_ptr_small_binind_get(ptr, mapbits);
tcache_dalloc_small(tcache, ptr, binind);
} else
arena_dalloc_small(arena, chunk, ptr, pageind);
arena_dalloc_small(chunk->arena, chunk, ptr, pageind);
} else {
size_t size = arena_mapbits_large_size_get(chunk, pageind);
@ -1053,7 +1050,7 @@ arena_dalloc(arena_t *arena, arena_chunk_t *chunk, void *ptr, bool try_tcache)
tcache_get(false)) != NULL) {
tcache_dalloc_large(tcache, ptr, size);
} else
arena_dalloc_large(arena, chunk, ptr);
arena_dalloc_large(chunk->arena, chunk, ptr);
}
}
# endif /* JEMALLOC_ARENA_INLINE_B */

2
include/jemalloc/internal/jemalloc_internal.h.in
View File

@ -895,7 +895,7 @@ idalloct(void *ptr, bool try_tcache)
chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
if (chunk != ptr)
arena_dalloc(chunk->arena, chunk, ptr, try_tcache);
arena_dalloc(chunk, ptr, try_tcache);
else
huge_dalloc(ptr, true);
}

2
src/jemalloc.c
View File

@ -2103,7 +2103,7 @@ a0free(void *ptr)
chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(ptr);
if (chunk != ptr)
arena_dalloc(chunk->arena, chunk, ptr, false);
arena_dalloc(chunk, ptr, false);
else
huge_dalloc(ptr, true);
}