project-base/server-skynet-source-3rd-jemalloc
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Enable fast thread locals for dealloc-only threads.

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Previously if a thread does only allocations, it stays on the slow path /
minimal initialized state forever.  However, dealloc-only is a valid pattern for
dedicated reclamation threads -- this means thread cache is disabled (no batched
flush) for them, which causes high overhead and contention.

Added the condition to fully initialize TSD when a fair amount of dealloc
activities are observed.
This commit is contained in:
Qi Wang
2022-10-21 15:10:48 -07:00
committed by Qi Wang
parent be65438f20
commit 143e9c4a2f
3 changed files with 77 additions and 1 deletions
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18
src/tsd.c
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@@ -300,9 +300,25 @@ tsd_fetch_slow(tsd_t *tsd, bool minimal) {
tsd_state_set(tsd, tsd_state_minimal_initialized);
tsd_set(tsd);
tsd_data_init_nocleanup(tsd);
*tsd_min_init_state_nfetchedp_get(tsd) = 1;
}
} else if (tsd_state_get(tsd) == tsd_state_minimal_initialized) {
if (!minimal) {
/*
* If a thread only ever deallocates (e.g. dedicated reclamation
* threads), we want to help it to eventually escape the slow
* path (caused by the minimal initialized state). The nfetched
* counter tracks the number of times the tsd has been accessed
* under the min init state, and triggers the switch to nominal
* once reached the max allowed count.
*
* This means at most 128 deallocations stay on the slow path.
*
* Also see comments in free_default().
*/
uint8_t *nfetched = tsd_min_init_state_nfetchedp_get(tsd);
assert(*nfetched >= 1);
(*nfetched)++;
if (!minimal || *nfetched == TSD_MIN_INIT_STATE_MAX_FETCHED) {
/* Switch to fully initialized. */
tsd_state_set(tsd, tsd_state_nominal);
assert(*tsd_reentrancy_levelp_get(tsd) >= 1);