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Adjust prefetch parameters. #15072

Merged
merged 1 commit into from
Jul 21, 2023
Merged

Adjust prefetch parameters. #15072

merged 1 commit into from
Jul 21, 2023

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amotin
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@amotin amotin commented Jul 16, 2023

  • Reduce maximum prefetch distance for 32bit platforms to 8MB as it was previously. Those systems didn't grow much probably, so better stay conservative there.
  • Retire array_rd_sz tunable, blocking prefetch for large requests. We should not penalize applications trying to be more efficient. The speculative prefetcher by itself has reasonable distance limits, and 1MB is not much at all these days.

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)

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@amotin amotin added the Status: Code Review Needed Ready for review and testing label Jul 16, 2023
allanjude
allanjude approved these changes Jul 17, 2023
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Reviewed-By: Allan Jude <[email protected]>

behlendorf
behlendorf approved these changes Jul 20, 2023
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include/sys/dmu_zfetch.h Show resolved Hide resolved
@amotin
Adjust prefetch parameters.
7939e0c 
 - Reduce maximum prefetch distance for 32bit platforms to 8MB as it
was previously.  Those systems didn't grow much probably, so better
stay conservative there.
 - Retire array_rd_sz tunable, blocking prefetch for large requests.
We should not penalize applications trying to be more efficient. The
speculative prefetcher by itself has reasonable distance limits, and
1MB is not much at all these days.

Signed-off-by:	Alexander Motin <[email protected]>
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 Jul 20, 2023
@behlendorf behlendorf merged commit 34b3d49 into openzfs:master Jul 21, 2023
behlendorf pushed a commit to behlendorf/zfs that referenced this pull request Jul 21, 2023
@amotin @behlendorf
Adjust prefetch parameters.
7150b16 
- Reduce maximum prefetch distance for 32bit platforms to 8MB as it
was previously.  Those systems didn't grow much probably, so better
stay conservative there.
 - Retire array_rd_sz tunable, blocking prefetch for large requests.
We should not penalize applications trying to be more efficient. The
speculative prefetcher by itself has reasonable distance limits, and
1MB is not much at all these days.

Reviewed-by: Allan Jude <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.
Closes openzfs#15072
behlendorf pushed a commit that referenced this pull request Jul 21, 2023
@amotin @behlendorf
Adjust prefetch parameters.
81be809 
- Reduce maximum prefetch distance for 32bit platforms to 8MB as it
was previously.  Those systems didn't grow much probably, so better
stay conservative there.
 - Retire array_rd_sz tunable, blocking prefetch for large requests.
We should not penalize applications trying to be more efficient. The
speculative prefetcher by itself has reasonable distance limits, and
1MB is not much at all these days.

Reviewed-by: Allan Jude <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.
Closes #15072
lundman pushed a commit to openzfsonwindows/openzfs that referenced this pull request Dec 12, 2023
@amotin @lundman
Adjust prefetch parameters.
4722ef9 
- Reduce maximum prefetch distance for 32bit platforms to 8MB as it
was previously.  Those systems didn't grow much probably, so better
stay conservative there.
 - Retire array_rd_sz tunable, blocking prefetch for large requests.
We should not penalize applications trying to be more efficient. The
speculative prefetcher by itself has reasonable distance limits, and
1MB is not much at all these days.

Reviewed-by: Allan Jude <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.
Closes openzfs#15072
@amotin amotin deleted the pref_dist branch March 22, 2024 16:35
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@behlendorf behlendorf behlendorf approved these changes

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