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8271064: ZGC several jvm08 perf regressions after JDK-8268372 #298

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@fisk fisk commented Aug 3, 2021

After the integration of ZGC dynamic thread selection, there was a regression that popped up on a few benchmarks that all had in common a high allocation rate and very quick GC times. An extra conservative measure for not trusting the heuristics when using few GC threads, did not play very well with this scenario. The effect of it is back-to-back GC causing thousands of GCs when <100 were really needed. Removing this conservative measure causes the regression to go away, and a bunch of green benchmarks to pop up instead of red ones. This suggest that conservative measure isn't working very well and does not scale to these scenarios. It is also already taken care of by other conservative measures. I propose it is removed, to solve the regressions.
The entire ZGC perf suite was rerun (no red, only green), and tier1-3 was run. There isn't much potential for things to blow up as I just removed one parameter in the heuristic. So if anything nasty was to show up, it would be in the perf runs.


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  • JDK-8271064: ZGC several jvm08 perf regressions after JDK-8268372

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@bridgekeeper bridgekeeper bot commented Aug 3, 2021

👋 Welcome back eosterlund! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

@openjdk openjdk bot added the rfr label Aug 3, 2021
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@openjdk openjdk bot commented Aug 3, 2021

@fisk The following label will be automatically applied to this pull request:

  • hotspot-gc

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added the hotspot-gc label Aug 3, 2021
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@mlbridge mlbridge bot commented Aug 3, 2021

Webrevs

pliden
pliden approved these changes Aug 3, 2021
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@pliden pliden left a comment

Looks good!

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@openjdk openjdk bot commented Aug 3, 2021

@fisk This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8271064: ZGC several jvm08 perf regressions after JDK-8268372

Reviewed-by: ayang, pliden, tschatzl

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At the time when this comment was updated there had been 2 new commits pushed to the master branch:

  • ada58d1: 8067223: [TESTBUG] Rename Whitebox API package
  • f8fb571: 8271150: Remove EA from JDK 17 version string starting with Initial RC promotion on Aug 5, 2021(B34)

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@fisk fisk commented Aug 3, 2021

Thanks for the reviews, @albertnetymk, @pliden and @tschatzl

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@fisk fisk commented Aug 4, 2021

/integrate

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@openjdk openjdk bot commented Aug 4, 2021

Going to push as commit 181483b.
Since your change was applied there have been 2 commits pushed to the master branch:

  • ada58d1: 8067223: [TESTBUG] Rename Whitebox API package
  • f8fb571: 8271150: Remove EA from JDK 17 version string starting with Initial RC promotion on Aug 5, 2021(B34)

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot closed this Aug 4, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels Aug 4, 2021
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@openjdk openjdk bot commented Aug 4, 2021

@fisk Pushed as commit 181483b.

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