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Use SEC in PAC to reduce lock contention on the ecaches

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Add a small extent cache in front of the PAC ecaches. Allocs and dallocs
that fit are served from per-shard SEC bins without taking the ecache
mutex; overflow falls through to the backing ecaches, including
ecache_pinned for pinned extents.

The feature is gated behind experimental_pac_sec_nshards (default 0,
disabled). To support independent HPA and PAC SEC instances,
sec_alloc/sec_dalloc/sec_fill take an explicit shard argument, with HPA
and PAC using separate TSD shard slots.
This commit is contained in:
Bin Liu 2026-05-19 00:11:15 -07:00 • committed by Guangli Dai
parent 2043c6ab58
commit 9c1a484e1d
19 changed files with 986 additions and 102 deletions
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38
src/stats.c
View file

@ -838,6 +838,37 @@ stats_arena_hpa_shard_sec_print(emitter_t *emitter, unsigned i) {
&sec_overfills);
}
static void
stats_arena_pac_sec_print(emitter_t *emitter, unsigned i) {
size_t sec_bytes;
size_t sec_hits;
size_t sec_misses;
size_t sec_dalloc_flush;
size_t sec_dalloc_noflush;
CTL_M2_GET("stats.arenas.0.pac_sec_bytes", i, &sec_bytes, size_t);
emitter_kv(emitter, "pac_sec_bytes",
"Bytes in PAC small extent cache",
emitter_type_size, &sec_bytes);
CTL_M2_GET("stats.arenas.0.pac_sec_hits", i, &sec_hits, size_t);
emitter_kv(emitter, "pac_sec_hits",
"Total hits in PAC small extent cache",
emitter_type_size, &sec_hits);
CTL_M2_GET("stats.arenas.0.pac_sec_misses", i, &sec_misses, size_t);
emitter_kv(emitter, "pac_sec_misses",
"Total misses in PAC small extent cache",
emitter_type_size, &sec_misses);
CTL_M2_GET("stats.arenas.0.pac_sec_dalloc_noflush", i,
&sec_dalloc_noflush, size_t);
emitter_kv(emitter, "pac_sec_dalloc_noflush",
"Dalloc calls without flush in PAC small extent cache",
emitter_type_size, &sec_dalloc_noflush);
CTL_M2_GET("stats.arenas.0.pac_sec_dalloc_flush", i, &sec_dalloc_flush,
size_t);
emitter_kv(emitter, "pac_sec_dalloc_flush",
"Dalloc calls with flush in PAC small extent cache",
emitter_type_size, &sec_dalloc_flush);
}
static void
stats_arena_hpa_shard_counters_print(
emitter_t *emitter, unsigned i, uint64_t uptime) {
@ -1570,6 +1601,10 @@ stats_arena_print(emitter_t *emitter, unsigned i, bool bins, bool large,
GET_AND_EMIT_MEM_STAT(extent_avail)
#undef GET_AND_EMIT_MEM_STAT
if (opt_pac_sec_opts.nshards > 0) {
stats_arena_pac_sec_print(emitter, i);
}
if (mutex) {
stats_arena_mutexes_print(emitter, i, uptime);
}
@ -1764,6 +1799,9 @@ stats_general_print(emitter_t *emitter) {
OPT_WRITE_SIZE_T("hpa_sec_nshards")
OPT_WRITE_SIZE_T("hpa_sec_max_alloc")
OPT_WRITE_SIZE_T("hpa_sec_max_bytes")
OPT_WRITE_SIZE_T("experimental_pac_sec_nshards")
OPT_WRITE_SIZE_T("experimental_pac_sec_max_alloc")
OPT_WRITE_SIZE_T("experimental_pac_sec_max_bytes")
OPT_WRITE_BOOL("huge_arena_pac_thp")
OPT_WRITE_CHAR_P("metadata_thp")
OPT_WRITE_INT64("mutex_max_spin")