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Allow metaslab to be unloaded even when not freed from #8837

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merged 1 commit into from
Jun 7, 2019

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Motivation and Context

On large systems, the memory used by loaded metaslabs can become a concern. While range trees are a fairly efficient data structure, on heavily fragmented pools they can still consume a significant amount of memory. This problem is amplified when we fail to unload metaslabs that we aren't using. Currently, we only unload a metaslab during metaslab_sync_done; in order for that function to be called on a given metaslab in a given txg, we have to have dirtied that metaslab in that txg. If the dirtying was the result of an allocation, we wouldn't be unloading it (since it wouldn't be 8 txgs since it was selected), so in effect we only unload a metaslab during txgs where it's being freed from.

Description

We move the unload logic from sync_done to a new function, and call that function on all metaslabs in a given vdev during vdev_sync_done().

How Has This Been Tested?

Extensive performance tests and correctness tests (zloop, zfs-test, integration tests with other software) have been performed on Illumos, and the zfs-test suite and zloop both passed on linux.

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)
  • Documentation (a change to man pages or other documentation)

Checklist:

Signed-off-by: Paul Dagnelie <pcd@delphix.com>
@behlendorf behlendorf added the Status: Code Review Needed Ready for review and testing label May 30, 2019
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metaslab_unload_delay is, by default, 8, leading to an expected nominal lifetime of 40 seconds. Does this lead to increased metaslab loads for idle systems? Has this been measured?

module/zfs/metaslab.c Show resolved Hide resolved
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codecov bot commented Jun 6, 2019

Codecov Report

Merging #8837 into master will increase coverage by 0.09%.
The diff coverage is 100%.

Impacted file tree graph

@@            Coverage Diff             @@
##           master    #8837      +/-   ##
==========================================
+ Coverage   78.72%   78.81%   +0.09%     
==========================================
  Files         382      382              
  Lines      117780   117809      +29     
==========================================
+ Hits        92723    92855     +132     
+ Misses      25057    24954     -103
Flag Coverage Δ
#kernel 79.36% <100%> (+0.03%) ⬆️
#user 67.52% <100%> (+0.34%) ⬆️

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@behlendorf behlendorf added Status: Accepted Ready to integrate (reviewed, tested) and removed Status: Code Review Needed Ready for review and testing labels Jun 6, 2019
@behlendorf behlendorf merged commit 893a6d6 into openzfs:master Jun 7, 2019
tonyhutter pushed a commit to tonyhutter/zfs that referenced this pull request Aug 13, 2019
On large systems, the memory used by loaded metaslabs can become
a concern. While range trees are a fairly efficient data structure,
on heavily fragmented pools they can still consume a significant
amount of memory. This problem is amplified when we fail to unload
metaslabs that we aren't using. Currently, we only unload a metaslab
during metaslab_sync_done; in order for that function to be called
on a given metaslab in a given txg, we have to have dirtied that
metaslab in that txg. If the dirtying was the result of an allocation,
we wouldn't be unloading it (since it wouldn't be 8 txgs since it
was selected), so in effect we only unload a metaslab during txgs
where it's being freed from.

We move the unload logic from sync_done to a new function, and
call that function on all metaslabs in a given vdev during
vdev_sync_done().

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes openzfs#8837
tonyhutter pushed a commit to tonyhutter/zfs that referenced this pull request Aug 22, 2019
On large systems, the memory used by loaded metaslabs can become
a concern. While range trees are a fairly efficient data structure,
on heavily fragmented pools they can still consume a significant
amount of memory. This problem is amplified when we fail to unload
metaslabs that we aren't using. Currently, we only unload a metaslab
during metaslab_sync_done; in order for that function to be called
on a given metaslab in a given txg, we have to have dirtied that
metaslab in that txg. If the dirtying was the result of an allocation,
we wouldn't be unloading it (since it wouldn't be 8 txgs since it
was selected), so in effect we only unload a metaslab during txgs
where it's being freed from.

We move the unload logic from sync_done to a new function, and
call that function on all metaslabs in a given vdev during
vdev_sync_done().

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes openzfs#8837
tonyhutter pushed a commit to tonyhutter/zfs that referenced this pull request Aug 23, 2019
On large systems, the memory used by loaded metaslabs can become
a concern. While range trees are a fairly efficient data structure,
on heavily fragmented pools they can still consume a significant
amount of memory. This problem is amplified when we fail to unload
metaslabs that we aren't using. Currently, we only unload a metaslab
during metaslab_sync_done; in order for that function to be called
on a given metaslab in a given txg, we have to have dirtied that
metaslab in that txg. If the dirtying was the result of an allocation,
we wouldn't be unloading it (since it wouldn't be 8 txgs since it
was selected), so in effect we only unload a metaslab during txgs
where it's being freed from.

We move the unload logic from sync_done to a new function, and
call that function on all metaslabs in a given vdev during
vdev_sync_done().

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes openzfs#8837
tonyhutter pushed a commit to tonyhutter/zfs that referenced this pull request Sep 17, 2019
On large systems, the memory used by loaded metaslabs can become
a concern. While range trees are a fairly efficient data structure,
on heavily fragmented pools they can still consume a significant
amount of memory. This problem is amplified when we fail to unload
metaslabs that we aren't using. Currently, we only unload a metaslab
during metaslab_sync_done; in order for that function to be called
on a given metaslab in a given txg, we have to have dirtied that
metaslab in that txg. If the dirtying was the result of an allocation,
we wouldn't be unloading it (since it wouldn't be 8 txgs since it
was selected), so in effect we only unload a metaslab during txgs
where it's being freed from.

We move the unload logic from sync_done to a new function, and
call that function on all metaslabs in a given vdev during
vdev_sync_done().

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes openzfs#8837
tonyhutter pushed a commit to tonyhutter/zfs that referenced this pull request Sep 18, 2019
On large systems, the memory used by loaded metaslabs can become
a concern. While range trees are a fairly efficient data structure,
on heavily fragmented pools they can still consume a significant
amount of memory. This problem is amplified when we fail to unload
metaslabs that we aren't using. Currently, we only unload a metaslab
during metaslab_sync_done; in order for that function to be called
on a given metaslab in a given txg, we have to have dirtied that
metaslab in that txg. If the dirtying was the result of an allocation,
we wouldn't be unloading it (since it wouldn't be 8 txgs since it
was selected), so in effect we only unload a metaslab during txgs
where it's being freed from.

We move the unload logic from sync_done to a new function, and
call that function on all metaslabs in a given vdev during
vdev_sync_done().

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes openzfs#8837
tonyhutter pushed a commit that referenced this pull request Sep 26, 2019
On large systems, the memory used by loaded metaslabs can become
a concern. While range trees are a fairly efficient data structure,
on heavily fragmented pools they can still consume a significant
amount of memory. This problem is amplified when we fail to unload
metaslabs that we aren't using. Currently, we only unload a metaslab
during metaslab_sync_done; in order for that function to be called
on a given metaslab in a given txg, we have to have dirtied that
metaslab in that txg. If the dirtying was the result of an allocation,
we wouldn't be unloading it (since it wouldn't be 8 txgs since it
was selected), so in effect we only unload a metaslab during txgs
where it's being freed from.

We move the unload logic from sync_done to a new function, and
call that function on all metaslabs in a given vdev during
vdev_sync_done().

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes #8837
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3 participants