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uma: Avoid excessive per-CPU draining

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After commit 389a3fa693, uma_reclaim_domain(UMA_RECLAIM_DRAIN_CPU)
calls uma_zone_reclaim_domain(UMA_RECLAIM_DRAIN_CPU) twice on each zone
in addition to globally draining per-CPU caches. This was unintended
and is unnecessarily slow; in particular, draining per-CPU caches
requires binding to each CPU.

Stop draining per-CPU caches when visiting each zone, just do it once in
pcpu_cache_drain_safe() to minimize the amount of expensive sched_bind()
calls.

Fixes:		389a3fa693 ("uma: Add UMA_ZONE_UNMANAGED")
MFC after:	1 week
Sponsored by:	Klara, Inc.
Sponsored by:	NetApp, Inc.
Reviewed by:	gallatin, kib
Differential Revision:	https://reviews.freebsd.org/D49349

(cherry picked from commit f506d5af50fccc37f5aa9fe090e9a0d5f05506c8)
This commit is contained in:
Mark Johnston 2025-03-17 20:12:58 +01:00 committed by Dag-Erling Smørgrav
parent a4251e93f8
commit 02324ae827
1 changed files with 7 additions and 0 deletions
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7
sys/vm/uma_core.c
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@ -5296,6 +5296,13 @@ uma_reclaim_domain(int req, int domain)
zone_foreach(uma_reclaim_domain_cb, &args);
break;
case UMA_RECLAIM_DRAIN_CPU:
/*
* Reclaim globally visible free items from all zones, then drain
* per-CPU buckets, then reclaim items freed while draining.
* This approach minimizes expensive context switching needed to
* drain each zone's per-CPU buckets.
*/
args.req = UMA_RECLAIM_DRAIN;
zone_foreach(uma_reclaim_domain_cb, &args);
pcpu_cache_drain_safe(NULL);
zone_foreach(uma_reclaim_domain_cb, &args);