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set zfs_arc_shrinker_limit to 0 by default #16909

Merged
merged 1 commit into from
Dec 29, 2024
Merged

set zfs_arc_shrinker_limit to 0 by default #16909

merged 1 commit into from
Dec 29, 2024

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shodanshok
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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.

Motivation and Context

See above.

Description

See above.

How Has This Been Tested?

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Performance enhancement (non-breaking change which improves efficiency)
  • Code cleanup (non-breaking change which makes code smaller or more readable)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
  • Documentation (a change to man pages or other documentation)

Checklist:

@shodanshok
set zfs_arc_shrinker_limit to 0 by default
86e8031 
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.

Signed-off-by: Gionatan Danti <[email protected]>
amotin
amotin approved these changes Dec 29, 2024
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I was proposing the same for a while, and it is a present default in TrueNAS.

@amotin amotin added the Status: Code Review Needed Ready for review and testing label Dec 29, 2024
behlendorf
behlendorf approved these changes Dec 29, 2024
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@behlendorf behlendorf left a comment

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Agreed, the time has come to make this change the default.

@behlendorf behlendorf added Status: Accepted Ready to integrate (reviewed, tested) and removed Status: Code Review Needed Ready for review and testing labels Dec 29, 2024
@behlendorf behlendorf merged commit 54126fd into openzfs:master Dec 29, 2024
25 of 26 checks passed
behlendorf pushed a commit to behlendorf/zfs that referenced this pull request Dec 29, 2024
@shodanshok @behlendorf
set zfs_arc_shrinker_limit to 0 by default
c2d9494 
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 <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Gionatan Danti <[email protected]>
Closes openzfs#16909
@amotin amotin mentioned this pull request Jan 23, 2025
Open
lundman pushed a commit to openzfsonwindows/openzfs that referenced this pull request Jan 26, 2025
@shodanshok @lundman
set zfs_arc_shrinker_limit to 0 by default
ca8c2be 
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 <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Gionatan Danti <[email protected]>
Closes openzfs#16909
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@amotin amotin amotin approved these changes

@behlendorf behlendorf behlendorf approved these changes

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@shodanshok @behlendorf @amotin