8289739: Add G1 specific GC breakpoints for testing

[tschatzl]

Hi all,

can I have reviews for this change that adds a few G1 specific GC breakpoints for future testing JDK-8289740.

Testing: gha, local testing

Thanks,
Thomas

---

Progress

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Issue

• JDK-8289739: Add G1 specific GC breakpoints for testing

Reviewers

• Kim Barrett (@kimbarrett - Reviewer)
• Ivan Walulya (@walulyai - Reviewer)

Reviewing

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[mlbridge]

Webrevs

• 00: Full (da566ff6)

[kimbarrett]

Looks good.

[openjdk]

@tschatzl 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:

8289739: Add G1 specific GC breakpoints for testing

Reviewed-by: kbarrett, iwalulya

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At the time when this comment was updated there had been 8 new commits pushed to the master branch:

• ac6be16: 8289695: [TESTBUG] TestMemoryAwareness.java fails on cgroups v2 and crun
• 4ad18cf: 8289730: Deprecated code sample in java.lang.ClassCastException
• d8f4e97: 8289146: containers/docker/TestMemoryWithCgroupV1.java fails on linux ppc64le machine with missing Memory and Swap Limit output
• f783244: 8289706: (cs) Avoid redundant TreeMap.containsKey call in AbstractCharsetProvider
• fafe8b3: 8289604: compiler/vectorapi/VectorLogicalOpIdentityTest.java failed on x86 AVX1 system
• 3515604: 8280481: Duplicated stubs to interpreter for static calls
• d48694d: 8283335: Add exists and readAttributesIfExists methods to FileSystemProvider
• c45d613: 8289687: [JVMCI] bug in HotSpotResolvedJavaMethodImpl.equals

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[albertnetymk]

It's unclear to me why "BEFORE REBUILD COMPLETED" is placed inside phase_cleanup; a more natural place to me is at the end of G1ConcurrentMarkThread::phase_rebuild_remembered_sets. (The same goes for the other pair of breakpoints.)

Sort of a preexisting issue but this change builds on top of it: "cleanup" can mean both the "cleanup pause" (phase_cleanup) or the "concurrent bitmap clearing" (phase_clear_bitmap_for_next_mark). IMO, it's better to get rid of such overloading.

(Not specific to this change. I also find the breakpoints naming pattern, before-X-started & after-X-completed, rather odd -- since they are breakpoints, names reflecting a particular point in time, instead of a period, would have been more accurate, sth like at-X-start & at-X-end.)

[tschatzl]

It's unclear to me why "BEFORE REBUILD COMPLETED" is placed inside phase_cleanup; a more natural place to me is at the end of G1ConcurrentMarkThread::phase_rebuild_remembered_sets. (The same goes for the other pair of breakpoints.)

(Concurrent) rebuild completes before the cleanup pause. This follows the existing scheme, e.g. in subphase_remark() there is the BEFORE MARKING COMPLETED breakpoint before the remark pause (which completes the marking).

The Cleanup pause is also a kind of extension of the rebuild remset phase as it acts on actually this information (and it has not been "cleaning up" anything relevant for a long time since JDK 11 iirc).

This seems to be a separate, pre-existing issue.

Sort of a preexisting issue but this change builds on top of it: "cleanup" can mean both the "cleanup pause" (phase_cleanup) or the "concurrent bitmap clearing" (phase_clear_bitmap_for_next_mark). IMO, it's better to get rid of such overloading.

The method names are different, one is called cleanup and the other clear_bitmap_for_next_mark phase for this reason. Maybe you suggest to rename the "Cleanup" pause and/or the "cleanup" use for the concurrent phase in the remaining code?

This renaming seems to be a separate (pre-existing) issue and related to above.

(Not specific to this change. I also find the breakpoints naming pattern, before-X-started & after-X-completed, rather odd -- since they are breakpoints, names reflecting a particular point in time, instead of a period, would have been more accurate, sth like at-X-start & at-X-end.)

The "at" seems to be more specific and could be changed separately and seems to be pre-existing.

[tschatzl]

Thanks @walulyai @kimbarrett for your reviews

/integrate

[openjdk]

Going to push as commit 8341895.
Since your change was applied there have been 8 commits pushed to the master branch:

• ac6be16: 8289695: [TESTBUG] TestMemoryAwareness.java fails on cgroups v2 and crun
• 4ad18cf: 8289730: Deprecated code sample in java.lang.ClassCastException
• d8f4e97: 8289146: containers/docker/TestMemoryWithCgroupV1.java fails on linux ppc64le machine with missing Memory and Swap Limit output
• f783244: 8289706: (cs) Avoid redundant TreeMap.containsKey call in AbstractCharsetProvider
• fafe8b3: 8289604: compiler/vectorapi/VectorLogicalOpIdentityTest.java failed on x86 AVX1 system
• 3515604: 8280481: Duplicated stubs to interpreter for static calls
• d48694d: 8283335: Add exists and readAttributesIfExists methods to FileSystemProvider
• c45d613: 8289687: [JVMCI] bug in HotSpotResolvedJavaMethodImpl.equals

Your commit was automatically rebased without conflicts.

[openjdk]

@tschatzl Pushed as commit 8341895.

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