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ZAP: Massively switch to _by_dnode() interfaces #15951

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merged 1 commit into from
Mar 25, 2024

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@amotin amotin commented Mar 1, 2024

Before this change ZAP called dnode_hold() for almost every block access, that was clearly visible in profiler under heavy load, such as BRT. This patch makes it always hold the dnode reference between zap_lockdir() and zap_unlockdir(). It allows to avoid most of dnode operations between those. It also adds several new _by_dnode() APIs to ZAP and uses them in BRT code. Also adds dmu_prefetch_by_dnode() variant and uses it in the ZAP code.

After this there remains only one call to dmu_buf_dnode_enter(), which seems to be unneeded. So remove the call and the functions.

How Has This Been Tested?

Created 700GB file and cloned it 3 times, collecting CPU profiles.

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:

include/sys/dmu.h Show resolved Hide resolved
module/zfs/zap.c Show resolved Hide resolved
@behlendorf
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It's good to see the addition of the new _by_dnode() functions and their use. I can easily believe that's a significant performance win.

@amotin amotin force-pushed the zap_by_dnode branch 2 times, most recently from 687ae94 to 8fdb724 Compare March 22, 2024 15:22
Before this change ZAP called dnode_hold() for almost every block
access, that was clearly visible in profiler under heavy load, such
as BRT.  This patch makes it always hold the dnode reference between
zap_lockdir() and zap_unlockdir().  It allows to avoid most of dnode
operations between those.  It also adds several new _by_dnode() APIs
to ZAP and uses them in BRT code.  Also adds dmu_prefetch_by_dnode()
variant and uses it in the ZAP code.

After this there remains only one call to dmu_buf_dnode_enter(),
which seems to be unneeded.  So remove the call and the functions.

Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
@behlendorf behlendorf added Status: Accepted Ready to integrate (reviewed, tested) and removed Status: Code Review Needed Ready for review and testing labels Mar 22, 2024
@behlendorf behlendorf merged commit 80cc516 into openzfs:master Mar 25, 2024
24 of 25 checks passed
@amotin amotin deleted the zap_by_dnode branch March 25, 2024 22:03
amotin added a commit to amotin/zfs that referenced this pull request Apr 17, 2024
Before this change ZAP called dnode_hold() for almost every block
access, that was clearly visible in profiler under heavy load, such
as BRT.  This patch makes it always hold the dnode reference between
zap_lockdir() and zap_unlockdir().  It allows to avoid most of dnode
operations between those.  It also adds several new _by_dnode() APIs
to ZAP and uses them in BRT code.  Also adds dmu_prefetch_by_dnode()
variant and uses it in the ZAP code.

After this there remains only one call to dmu_buf_dnode_enter(),
which seems to be unneeded.  So remove the call and the functions.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes openzfs#15951
behlendorf pushed a commit that referenced this pull request Apr 19, 2024
Before this change ZAP called dnode_hold() for almost every block
access, that was clearly visible in profiler under heavy load, such
as BRT.  This patch makes it always hold the dnode reference between
zap_lockdir() and zap_unlockdir().  It allows to avoid most of dnode
operations between those.  It also adds several new _by_dnode() APIs
to ZAP and uses them in BRT code.  Also adds dmu_prefetch_by_dnode()
variant and uses it in the ZAP code.

After this there remains only one call to dmu_buf_dnode_enter(),
which seems to be unneeded.  So remove the call and the functions.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15951
lundman pushed a commit to openzfsonwindows/openzfs that referenced this pull request Sep 4, 2024
Before this change ZAP called dnode_hold() for almost every block
access, that was clearly visible in profiler under heavy load, such
as BRT.  This patch makes it always hold the dnode reference between
zap_lockdir() and zap_unlockdir().  It allows to avoid most of dnode
operations between those.  It also adds several new _by_dnode() APIs
to ZAP and uses them in BRT code.  Also adds dmu_prefetch_by_dnode()
variant and uses it in the ZAP code.

After this there remains only one call to dmu_buf_dnode_enter(),
which seems to be unneeded.  So remove the call and the functions.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes openzfs#15951
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2 participants