Make txg_wait_synced conditional in zfsvfs_teardown #9115

PaulZ-98 · 2019-08-02T13:21:10Z

The call to txg_wait_synced in zfsvfs_teardown should
be made conditional on the objset having dirty data.
This can prevent unnecessary txg_wait_synced during
some unmount operations.

Signed-off-by: Paul Zuchowski pzuchowski@datto.com

The function zfsvfs_teardown only skips txg_wait_synced if the objset is read-only. We can also avoid txg_wait_synced if the objset has no dirty data. Detect if the objset is dirty and don't call txg_wait_synced if it is not.

Motivation and Context

Applications that perform lots of sync tasks are already forcing txg_wait_synced. If the application also limits ZFS mounts by unmounting datasets after use, it could be helpful to performance to avoid txg_wait_synced during unmount when we can.

Description

Add to the conditional test for txg_wait_synced in zfsvfs_teardown.

How Has This Been Tested?

Ran the zfs test suite.

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:

My code follows the ZFS on Linux code style requirements.
I have updated the documentation accordingly.
I have read the contributing document.
I have added tests to cover my changes.
All new and existing tests passed.
All commit messages are properly formatted and contain Signed-off-by.

ahrens · 2019-08-05T18:30:35Z

module/zfs/zfs_vfsops.c

+	for (int t = 0; t < TXG_SIZE; t++) {
+		os_dirty = dmu_objset_is_dirty(os, t);
+		if (os_dirty)
+			break;


[nit] I think this would be slightly easier to read as:

if (dmu_objset_is_dirty(...)) { os_dirty = B_TRUE; break; }

Thanks Matt I made that change.

The call to txg_wait_synced in zfsvfs_teardown should be made conditional on the objset having dirty data. This can prevent unnecessary txg_wait_synced during some unmount operations. Signed-off-by: Paul Zuchowski <pzuchowski@datto.com>

codecov · 2019-08-06T12:46:13Z

Codecov Report

Merging #9115 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #9115      +/-   ##
==========================================
+ Coverage   79.18%   79.21%   +0.02%     
==========================================
  Files         400      400              
  Lines      121692   121656      -36     
==========================================
+ Hits        96360    96367       +7     
+ Misses      25332    25289      -43

Flag	Coverage Δ
#kernel	`79.72% <100%> (+0.04%)`	⬆️
#user	`67.4% <ø> (+0.35%)`	⬆️

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The call to txg_wait_synced in zfsvfs_teardown should be made conditional on the objset having dirty data. This can prevent unnecessary txg_wait_synced during some unmount operations. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Zuchowski <pzuchowski@datto.com> Closes openzfs#9115

The call to txg_wait_synced in zfsvfs_teardown should be made conditional on the objset having dirty data. This can prevent unnecessary txg_wait_synced during some unmount operations. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Zuchowski <pzuchowski@datto.com> Closes #9115

The call to txg_wait_synced in zfsvfs_teardown should be made conditional on the objset having dirty data. This can prevent unnecessary txg_wait_synced during some unmount operations. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Zuchowski <pzuchowski@datto.com> Closes openzfs#9115 Signed-off-by: Bryant G. Ly <bly@catalogicsoftware.com> Conflicts: module/zfs/zfs_vfsops.c

@mattmacy

This applies the same change in openzfs#9115 to FreeBSD. This was actually the old behavior in FreeBSD 12; it only regressed when FreeBSD support was added to OpenZFS. As far as I can tell, the timeline went like this: * Illumos's zfsvfs_teardown used an unconditional txg_wait_synced * Illumos added the dirty data check [^4] * FreeBSD merged in Illumos's conditional check [^3] * OpenZFS forked from Illumos * OpenZFS removed the dirty data check in openzfs#7795 [^5] * @mattmacy forked the OpenZFS repo and began to add FreeBSD support * OpenZFS PR openzfs#9115[^1] recreated the same dirty data check that Illumos used, in slightly different form. At this point the OpenZFS repo did not yet have multi-OS support. * Matt Macy merged in FreeBSD support in openzfs#8987[^2] , but it was based on slightly outdated OpenZFS code. In my local testing, this vastly improves the reboot speed of a server with a large pool that has 1000 datasets and is resilvering an HDD. [^1]: openzfs#9115 [^2]: openzfs#8987 [^3]: freebsd/freebsd-src@10b9d77 [^4]: illumos/illumos-gate@5aaeed5 [^5]: openzfs#7795 Sponsored by: Axcient Signed-off-by: Alan Somers <asomers@gmail.com>

@mattmacy

This applies the same change in #9115 to FreeBSD. This was actually the old behavior in FreeBSD 12; it only regressed when FreeBSD support was added to OpenZFS. As far as I can tell, the timeline went like this: * Illumos's zfsvfs_teardown used an unconditional txg_wait_synced * Illumos added the dirty data check [^4] * FreeBSD merged in Illumos's conditional check [^3] * OpenZFS forked from Illumos * OpenZFS removed the dirty data check in #7795 [^5] * @mattmacy forked the OpenZFS repo and began to add FreeBSD support * OpenZFS PR #9115[^1] recreated the same dirty data check that Illumos used, in slightly different form. At this point the OpenZFS repo did not yet have multi-OS support. * Matt Macy merged in FreeBSD support in #8987[^2] , but it was based on slightly outdated OpenZFS code. In my local testing, this vastly improves the reboot speed of a server with a large pool that has 1000 datasets and is resilvering an HDD. [^1]: #9115 [^2]: #8987 [^3]: freebsd/freebsd-src@10b9d77 [^4]: illumos/illumos-gate@5aaeed5 [^5]: #7795 Sponsored by: Axcient Reviewed-by: Allan Jude <allan@klarasystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Alan Somers <asomers@gmail.com> Closes #16268

@mattmacy

This applies the same change in openzfs#9115 to FreeBSD. This was actually the old behavior in FreeBSD 12; it only regressed when FreeBSD support was added to OpenZFS. As far as I can tell, the timeline went like this: * Illumos's zfsvfs_teardown used an unconditional txg_wait_synced * Illumos added the dirty data check [^4] * FreeBSD merged in Illumos's conditional check [^3] * OpenZFS forked from Illumos * OpenZFS removed the dirty data check in openzfs#7795 [^5] * @mattmacy forked the OpenZFS repo and began to add FreeBSD support * OpenZFS PR openzfs#9115[^1] recreated the same dirty data check that Illumos used, in slightly different form. At this point the OpenZFS repo did not yet have multi-OS support. * Matt Macy merged in FreeBSD support in openzfs#8987[^2] , but it was based on slightly outdated OpenZFS code. In my local testing, this vastly improves the reboot speed of a server with a large pool that has 1000 datasets and is resilvering an HDD. [^1]: openzfs#9115 [^2]: openzfs#8987 [^3]: freebsd/freebsd-src@10b9d77 [^4]: illumos/illumos-gate@5aaeed5 [^5]: openzfs#7795 Sponsored by: Axcient Reviewed-by: Allan Jude <allan@klarasystems.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Alan Somers <asomers@gmail.com> Closes openzfs#16268

ahrens added Status: Code Review Needed Ready for review and testing Type: Performance Performance improvement or performance problem labels Aug 5, 2019

ahrens approved these changes Aug 5, 2019

View reviewed changes

ahrens requested a review from grwilson August 5, 2019 18:31

PaulZ-98 force-pushed the unmount_fix branch from 6fc830d to 16e8c2d Compare August 6, 2019 12:45

behlendorf approved these changes Aug 12, 2019

View reviewed changes

behlendorf added Status: Accepted Ready to integrate (reviewed, tested) and removed Status: Code Review Needed Ready for review and testing labels Aug 14, 2019

behlendorf merged commit e2b31b5 into openzfs:master Aug 15, 2019

This was referenced Jun 14, 2024

Make txg_wait_synced conditional in zfsvfs_teardown, for FreeBSD #16268

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Possible regression when unmounting encrypted datasets. #16269

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Make txg_wait_synced conditional in zfsvfs_teardown #9115

Make txg_wait_synced conditional in zfsvfs_teardown #9115

PaulZ-98 commented Aug 2, 2019

ahrens Aug 5, 2019

PaulZ-98 Aug 6, 2019

codecov bot commented Aug 6, 2019 •

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Make txg_wait_synced conditional in zfsvfs_teardown #9115

Make txg_wait_synced conditional in zfsvfs_teardown #9115

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PaulZ-98 commented Aug 2, 2019

Motivation and Context

Description

How Has This Been Tested?

Types of changes

Checklist:

ahrens Aug 5, 2019

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