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set zfs_arc_shrinker_limit to 0 by default

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zfs_arc_shrinker_limit was introduced to avoid ARC collapse due to
aggressive kernel reclaim. While useful, the current default (10000) is
too prone to OOM especially when MGLRU-enabled kernels with default
min_ttl_ms are used. Even when no OOM happens, it often causes too much
swap usage.

This patch sets zfs_arc_shrinker_limit=0 to not ignore kernel reclaim
requests. ARC now plays better with both kernel shrinker and pagecache
but, should ARC collapse happen again, MGLRU behavior can be tuned or
even disabled.

Anyway, zfs should not cause OOM when ARC can be released.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Gionatan Danti <g.danti@assyoma.it>
Closes #16909
This commit is contained in:
shodanshok
2024-12-29 20:50:19 +01:00
committed by GitHub
parent 9dd5fe1095
commit 54126fdb5b
2 changed files with 4 additions and 4 deletions
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man/man4/zfs.4
+2 -2
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@@ -867,14 +867,14 @@ where that percent may exceed
This
only operates during memory pressure/reclaim.
.
.It Sy zfs_arc_shrinker_limit Ns = Ns Sy 10000 Pq int
.It Sy zfs_arc_shrinker_limit Ns = Ns Sy 0 Pq int
This is a limit on how many pages the ARC shrinker makes available for
eviction in response to one page allocation attempt.
Note that in practice, the kernel's shrinker can ask us to evict
up to about four times this for one allocation attempt.
To reduce OOM risk, this limit is applied for kswapd reclaims only.
.Pp
The default limit of
For example a value of
.Sy 10000 Pq in practice, Em 160 MiB No per allocation attempt with 4 KiB pages
limits the amount of time spent attempting to reclaim ARC memory to
less than 100 ms per allocation attempt,