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Fix for "Reduce latency effects of non-interactive I/O". #11261

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merged 1 commit into from
Dec 3, 2020
Merged

Fix for "Reduce latency effects of non-interactive I/O". #11261

merged 1 commit into from
Dec 3, 2020

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@amotin amotin commented Dec 1, 2020

It was found that setting min_active tunables for non-interactive I/Os makes them stuck. It is caused by zfs_vdev_nia_delay, that can never be reached if we never issue any I/Os due to min_active set to zero.

Fix this by issuing at least one non-interactive I/O at a time when there are no interactive I/Os. When there are interactive I/Os, zero min_active allows to completely block any non-interactive I/O. It may cause bad starvation in some scenarios, but who we are to deny foot shooting?

Closing: #11245

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)

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@amotin amotin self-assigned this Dec 1, 2020
@amotin amotin requested a review from a user December 1, 2020 18:16
@amotin amotin mentioned this pull request Dec 1, 2020
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@amotin amotin requested review from ahrens and behlendorf December 1, 2020 18:18
@amotin amotin added the Status: Code Review Needed Ready for review and testing label Dec 1, 2020
@amotin
Fix for "Reduce latency effects of non-interactive I/O".
0c081db 
It was found that setting min_active tunables for non-interactive I/Os
makes them stuck.  It is caused by zfs_vdev_nia_delay, that can never
be reached if we never issue any I/Os due to min_active set to zero.

Fix this by issuing at least one non-interactive I/O at a time when
there are no interactive I/Os.  When there are interactive I/Os, zero
min_active allows to completely block any non-interactive I/O.  It may
min_active starvation in some scenarios, but who we are to deny foot
shooting?

Signed-off-by: Alexander Motin <[email protected]>
ghost
ghost approved these changes Dec 1, 2020
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Ah, so that person had set one of these to 0. Sneaky :)

@behlendorf behlendorf added Status: Accepted Ready to integrate (reviewed, tested) and removed Status: Code Review Needed Ready for review and testing labels Dec 2, 2020
@behlendorf behlendorf merged commit dcf7044 into openzfs:master Dec 3, 2020
@amotin amotin deleted the nia_throttle2 branch December 3, 2020 18:05
ghost pushed a commit to zfsonfreebsd/ZoF that referenced this pull request Dec 23, 2020
@amotin
Fix for "Reduce latency effects of non-interactive I/O"
b0b0439 
It was found that setting min_active tunables for non-interactive I/Os
makes them stuck.  It is caused by zfs_vdev_nia_delay, that can never
be reached if we never issue any I/Os due to min_active set to zero.

Fix this by issuing at least one non-interactive I/O at a time when
there are no interactive I/Os.  When there are interactive I/Os, zero
min_active allows to completely block any non-interactive I/O.  It may
min_active starvation in some scenarios, but who we are to deny foot
shooting?

Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Closes openzfs#11261
behlendorf pushed a commit that referenced this pull request Dec 23, 2020
@amotin @behlendorf
Fix for "Reduce latency effects of non-interactive I/O"
1d02bde 
It was found that setting min_active tunables for non-interactive I/Os
makes them stuck.  It is caused by zfs_vdev_nia_delay, that can never
be reached if we never issue any I/Os due to min_active set to zero.

Fix this by issuing at least one non-interactive I/O at a time when
there are no interactive I/Os.  When there are interactive I/Os, zero
min_active allows to completely block any non-interactive I/O.  It may
min_active starvation in some scenarios, but who we are to deny foot
shooting?

Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Closes #11261
jsai20 pushed a commit to jsai20/zfs that referenced this pull request Mar 30, 2021
@amotin @jsai20
Fix for "Reduce latency effects of non-interactive I/O"
748fb11 
It was found that setting min_active tunables for non-interactive I/Os
makes them stuck.  It is caused by zfs_vdev_nia_delay, that can never
be reached if we never issue any I/Os due to min_active set to zero.

Fix this by issuing at least one non-interactive I/O at a time when
there are no interactive I/Os.  When there are interactive I/Os, zero
min_active allows to completely block any non-interactive I/O.  It may
min_active starvation in some scenarios, but who we are to deny foot
shooting?

Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Closes openzfs#11261
sempervictus pushed a commit to sempervictus/zfs that referenced this pull request May 31, 2021
@amotin
Fix for "Reduce latency effects of non-interactive I/O"
b996187 
It was found that setting min_active tunables for non-interactive I/Os
makes them stuck.  It is caused by zfs_vdev_nia_delay, that can never
be reached if we never issue any I/Os due to min_active set to zero.

Fix this by issuing at least one non-interactive I/O at a time when
there are no interactive I/Os.  When there are interactive I/Os, zero
min_active allows to completely block any non-interactive I/O.  It may
min_active starvation in some scenarios, but who we are to deny foot
shooting?

Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Closes openzfs#11261
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@gmelikov gmelikov gmelikov approved these changes

@behlendorf behlendorf behlendorf approved these changes

@ahrens ahrens Awaiting requested review from ahrens

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