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runtime: GC pacing exhibits strange behavior with a low GOGC [1.14 backport] #37928

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gopherbot opened this issue Mar 18, 2020 · 3 comments
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runtime: GC pacing exhibits strange behavior with a low GOGC [1.14 backport] #37928

gopherbot opened this issue Mar 18, 2020 · 3 comments
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CherryPickApproved Used during the release process for point releases FrozenDueToAge
Milestone
Go1.14.2

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@gopherbot
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@ianlancetaylor requested issue #37927 to be considered for backport to the next 1.14 minor release.

@gopherbot Please open a backport to 1.14. The comment above suggests that we should do this to fix GOGC in 1.14.
@gopherbot gopherbot added the CherryPickCandidate Used during the release process for point releases label Mar 18, 2020
@gopherbot gopherbot mentioned this issue Mar 18, 2020
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@gopherbot gopherbot added this to the Go1.14.1 milestone Mar 18, 2020
@cagedmantis cagedmantis modified the milestones: Go1.14.1, Go1.14.2 Mar 19, 2020
@cagedmantis
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Approved. It's a serious issue without a known workaround.

@cagedmantis cagedmantis added CherryPickApproved Used during the release process for point releases and removed CherryPickCandidate Used during the release process for point releases labels Mar 20, 2020
@gopherbot
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Change https://golang.org/cl/225637 mentions this issue: [release-branch.go1.14] runtime: ensure minTriggerRatio never exceeds maxTriggerRatio

@mknyszek mknyszek self-assigned this Mar 26, 2020
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Closed by merging 9d7dad1 to release-branch.go1.14.

gopherbot pushed a commit that referenced this issue Mar 27, 2020
@mknyszek @ianlancetaylor
[release-branch.go1.14] runtime: ensure minTriggerRatio never exceeds…
9d7dad1 
… maxTriggerRatio

Currently, the capping logic for the GC trigger ratio is such that if
gcpercent is low, we may end up setting the trigger ratio far too high,
breaking the promise of SetGCPercent and GOGC has a trade-off knob (we
won't start a GC early enough, and we will use more memory).

This change modifies the capping logic for the trigger ratio by scaling
the minTriggerRatio with gcpercent the same way we scale
maxTriggerRatio.

For #37927.
Fixes #37928.

Change-Id: I2a048c1808fb67186333d3d5a6bee328be2f35da
Reviewed-on: https://go-review.googlesource.com/c/go/+/223937
Run-TryBot: Michael Knyszek <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
(cherry picked from commit d1ecfcc)
Reviewed-on: https://go-review.googlesource.com/c/go/+/225637
Reviewed-by: David Chase <[email protected]>
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