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Use tsd offset_state instead of atomic

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While working on #852, I noticed the prng state is atomic.  This is the only
atomic use of prng in all of jemalloc.  Instead, use a threadlocal prng
state if possible to avoid unnecessary cache line contention.
This commit is contained in:
Dave Watson 2017-10-13 10:27:13 -07:00
parent cb3b72b975
commit d6feed6e66
3 changed files with 22 additions and 3 deletions
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13
include/jemalloc/internal/extent_inlines.h
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@ -196,9 +196,16 @@ extent_addr_randomize(tsdn_t *tsdn, extent_t *extent, size_t alignment) {
if (alignment < PAGE) { if (alignment < PAGE) {
unsigned lg_range = LG_PAGE - unsigned lg_range = LG_PAGE -
lg_floor(CACHELINE_CEILING(alignment)); lg_floor(CACHELINE_CEILING(alignment));
size_t r = size_t r;
prng_lg_range_zu(&extent_arena_get(extent)->offset_state, if (!tsdn_null(tsdn)) {
lg_range, true); tsd_t *tsd = tsdn_tsd(tsdn);
r = (size_t)prng_lg_range_u64(
tsd_offset_statep_get(tsd), lg_range);
} else {
r = prng_lg_range_zu(
&extent_arena_get(extent)->offset_state,
lg_range, true);
}
uintptr_t random_offset = ((uintptr_t)r) << (LG_PAGE - uintptr_t random_offset = ((uintptr_t)r) << (LG_PAGE -
lg_range); lg_range);
extent->e_addr = (void *)((uintptr_t)extent->e_addr + extent->e_addr = (void *)((uintptr_t)extent->e_addr +

2
include/jemalloc/internal/tsd.h
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@ -65,6 +65,7 @@ typedef void (*test_callback_t)(int *);
O(arenas_tdata_bypass, bool, bool) \ O(arenas_tdata_bypass, bool, bool) \
O(reentrancy_level, int8_t, int8_t) \ O(reentrancy_level, int8_t, int8_t) \
O(narenas_tdata, uint32_t, uint32_t) \ O(narenas_tdata, uint32_t, uint32_t) \
O(offset_state, uint64_t, uint64_t) \
O(thread_allocated, uint64_t, uint64_t) \ O(thread_allocated, uint64_t, uint64_t) \
O(thread_deallocated, uint64_t, uint64_t) \ O(thread_deallocated, uint64_t, uint64_t) \
O(prof_tdata, prof_tdata_t *, prof_tdata_t *) \ O(prof_tdata, prof_tdata_t *, prof_tdata_t *) \
@ -84,6 +85,7 @@ typedef void (*test_callback_t)(int *);
0, \ 0, \
0, \ 0, \
0, \ 0, \
0, \
NULL, \ NULL, \
RTREE_CTX_ZERO_INITIALIZER, \ RTREE_CTX_ZERO_INITIALIZER, \
NULL, \ NULL, \

10
src/tsd.c
View File

@ -71,6 +71,16 @@ tsd_data_init(tsd_t *tsd) {
*/ */
rtree_ctx_data_init(tsd_rtree_ctxp_get_unsafe(tsd)); rtree_ctx_data_init(tsd_rtree_ctxp_get_unsafe(tsd));
/*
* A nondeterministic seed based on the address of tsd reduces
* the likelihood of lockstep non-uniform cache index
* utilization among identical concurrent processes, but at the
* cost of test repeatability. For debug builds, instead use a
* deterministic seed.
*/
*tsd_offset_statep_get(tsd) = config_debug ? 0 :
(uint64_t)(uintptr_t)tsd;
return tsd_tcache_enabled_data_init(tsd); return tsd_tcache_enabled_data_init(tsd);
} }