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8278146: G1: Rework VM_G1Concurrent VMOp to clearly identify it as pause #6677

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shipilev
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@shipilev shipilev commented Dec 2, 2021

Our support engineers asked this:

I see these G1Concurrent safepoints in JDK17:
[0.064s][info][safepoint ] Safepoint "G1Concurrent", Time since last: 1666947 ns, Reaching
safepoint: 79150 ns, At safepoint: 349999 ns, Total: 429149 ns
I've always thought that "concurrent" and "safepoint" are basically antonyms.
What is a G1Concurrent safepoint? How can a concurrent event require a safepoint?

I agree that's confusing. This patch splits the VM_G1Concurrent into two exactly named VMOp-s, so that we get:

[6.527s][info][gc       ] GC(7) Pause Remark 64M->64M(224M) 218.847ms
[6.527s][info][safepoint] Safepoint "G1PauseRemark", Time since last: 17493991 ns, Reaching safepoint: 506830 ns, At safepoint: 218950374 ns, Total: 219457204 ns
[6.536s][info][gc       ] GC(7) Pause Cleanup 71M->71M(224M) 0.177ms
[6.536s][info][safepoint] Safepoint "G1PauseCleanup", Time since last: 8250157 ns, Reaching safepoint: 884967 ns, At safepoint: 223964 ns, Total: 1108931 ns
[6.537s][info][gc       ] GC(7) Concurrent Mark Cycle 247.051ms

Additional testing:

  • Linux x86_64 fastdebug tier1

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  • Change must not contain extraneous whitespace
  • Commit message must refer to an issue
  • Change must be properly reviewed

Issue

  • JDK-8278146: G1: Rework VM_G1Concurrent VMOp to clearly identify it as pause

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Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6677/head:pull/6677
$ git checkout pull/6677

Update a local copy of the PR:
$ git checkout pull/6677
$ git pull https://git.openjdk.java.net/jdk pull/6677/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 6677

View PR using the GUI difftool:
$ git pr show -t 6677

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6677.diff

@shipilev shipilev changed the title 8278146: G1: Rework VM_G1Concurrent vmOp to clearly identify it as pause 8278146: G1: Rework VM_G1Concurrent VMOp to clearly identify it as pause Dec 2, 2021
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@bridgekeeper bridgekeeper bot commented Dec 2, 2021

👋 Welcome back shade! 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 Dec 2, 2021
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@openjdk openjdk bot commented Dec 2, 2021

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

  • hotspot

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 label Dec 2, 2021
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@tschatzl tschatzl left a comment

Lgtm.

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@openjdk openjdk bot commented Dec 7, 2021

@shipilev 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:

8278146: G1: Rework VM_G1Concurrent VMOp to clearly identify it as pause

Reviewed-by: tschatzl, kbarrett

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At the time when this comment was updated there had been no new commits pushed to the master branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential automatic rebasing, please check the documentation for the /integrate command for further details.

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@openjdk openjdk bot added the ready label Dec 7, 2021
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@shipilev shipilev commented Dec 8, 2021

Thanks @tschatzl! Latest GHA are green: https://github.com/shipilev/jdk/actions/runs/1545801216

I think I need a second review?

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@kimbarrett kimbarrett left a comment

Looks good. Regarding suggestions to use override, I don't need a re-review if you make those changes.

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@shipilev shipilev commented Dec 20, 2021

Looks good. Regarding suggestions to use override, I don't need a re-review if you make those changes.

Thanks, added override. It looks to me that the Hotspot style is to carry virtual only on the superclass declaration, and do override on all subclass overrides, dropping explicit virtual for them. True? See new commit that does that.

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@tschatzl tschatzl left a comment

Still good.

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@shipilev shipilev commented Jan 3, 2022

Thanks! I am retesting for new master, and then integrating.

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@shipilev shipilev commented Jan 3, 2022

/integrate

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@openjdk openjdk bot commented Jan 3, 2022

Going to push as commit 3a1fca3.

@openjdk openjdk bot added the integrated label Jan 3, 2022
@openjdk openjdk bot closed this Jan 3, 2022
@openjdk openjdk bot removed ready rfr labels Jan 3, 2022
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@openjdk openjdk bot commented Jan 3, 2022

@shipilev Pushed as commit 3a1fca3.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

@shipilev shipilev deleted the JDK-8278146-g1-concurrent-vmop branch Jan 5, 2022
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