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Avoid arena->offset_state when tsd not available for prng.

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Use stack locals and remove the offset_state in arena.
This commit is contained in:
Qi Wang 2019-11-04 16:44:37 -08:00 committed by Qi Wang
parent d01b425e5d
commit 19a51abf33
3 changed files with 2 additions and 22 deletions
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8
include/jemalloc/internal/arena_structs.h
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@ -118,14 +118,6 @@ struct arena_s {
/* Synchronization: internal. */
prof_accum_t prof_accum;
/*
* PRNG state for cache index randomization of large allocation base
* pointers.
*
* Synchronization: atomic.
*/
atomic_zu_t offset_state;
/*
* Extent serial number generator state.
*

12
src/arena.c
View File

@ -1981,18 +1981,6 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
}
}
if (config_cache_oblivious) {
/*
* A nondeterministic seed based on the address of arena 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.
*/
atomic_store_zu(&arena->offset_state, config_debug ? ind :
(size_t)(uintptr_t)arena, ATOMIC_RELAXED);
}
atomic_store_zu(&arena->extent_sn_next, 0, ATOMIC_RELAXED);
atomic_store_u(&arena->dss_prec, (unsigned)extent_dss_prec_get(),

4
src/extent.c
View File

@ -187,8 +187,8 @@ extent_addr_randomize(tsdn_t *tsdn, arena_t *arena, extent_t *extent,
r = (size_t)prng_lg_range_u64(
tsd_offset_statep_get(tsd), lg_range);
} else {
r = prng_lg_range_zu(&arena->offset_state, lg_range,
true);
uint64_t stack_value = (uint64_t)(uintptr_t)&r;
r = (size_t)prng_lg_range_u64(&stack_value, lg_range);
}
uintptr_t random_offset = ((uintptr_t)r) << (LG_PAGE -
lg_range);