8300769: Remove G1CollectionSet::_inc_bytes_used_before

[tschatzl]

Hi all,

please review this removal of G1CollectionSet::_inc_bytes_used_before; this variable holds the amount of bytes used in eden regions, updated during mutator time. At the start of gc its value is copied to G1CollectionSet::_bytes_used_before, and then never touched again. The _bytes_used_before is read at end of gc, and then reset.

This change simply removes _inc_bytes_used_before and directly uses _bytes_used_before to accumulate eden region used bytes.

Testing: gha

Thanks,
Thomas

---

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Issue

• JDK-8300769: Remove G1CollectionSet::_inc_bytes_used_before

Reviewers

• Albert Mingkun Yang (@albertnetymk - Reviewer) ⚠️ Review applies to cbf4de63
• Ivan Walulya (@walulyai - Reviewer) ⚠️ Review applies to cbf4de63

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• 03: Full - Incremental (7220ffa5)
• 02: Full (cbf4de63)
• 01: Full - Incremental (b15485bb)
• 00: Full (ec60055c)

[albertnetymk]

I think _bytes_used is enough; the _before suffix adds nothing and it's confusing -- there's no counterpart like _bytes_used_after.

[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:

8300769: Remove G1CollectionSet::_inc_bytes_used_before

Reviewed-by: ayang, iwalulya

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 27 new commits pushed to the master branch:

• 859ca75: 8300862: Remove some G1 collection set remembered set debugging code
• 048705c: 8300910: Remove metaprogramming/integralConstant.hpp
• 544c16e: 8300266: Detect Virtualization on Linux aarch64
• 57f2d48: 8300863: Remove C-style array declarations in java.io
• 2292ce1: 8294677: chunklevel::MAX_CHUNK_WORD_SIZE too small for some applications
• 6dd8723: 8290918: Initial nroff manpage generation for JDK 21
• b3822f5: 8300589: Use @snippet and @linkplain in java.text.CollationKey and java.text.CompactNumberFormat
• afd5921: 8298610: Refactor archiving of ConstantPool::resolved_references()
• 937ba1c: 8300111: Add rpath for common lib locations for jpackageapplauncher
• 2da2e5a: 8300946: Add sun/security/provider/certpath/OCSP/OCSPNoContentLength to ProblemList
• ... and 17 more: https://git.openjdk.org/jdk/compare/5a4945c0d95423d0ab07762c915e9cb4d3c66abb...master

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.

[tschatzl]

I think _bytes_used is enough; the _before suffix adds nothing and it's confusing -- there's no counterpart like _bytes_used_after.

I considered that, but you could argue that the metric gathered here is "bytes used before" (gc, in the collection set). The "bytes used after" is calculated on the spot when it's needed just before passing it on to JFR.
I'm good either way, if you still think it's better to remove the _before or the second reviewer suggests it too, I'll do the rename (in another RFE).

[walulyai]

Lgtm!

[openjdk]

@tschatzl this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout submit/8300769-remove-inc_bytes_used_before
git fetch https://git.openjdk.org/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[tschatzl]

@albertnetymk found that actually the information of _byte_used_before can be recreated from FreeCSetStats, so G1CollectionSet::_bytes_used_before can be removed as well.
Further I fixed the merge errors with latest version.

[walulyai]

Better!

[tschatzl]

Thanks for your reviews
/integrate

[openjdk]

Going to push as commit 3be5758.
Since your change was applied there have been 27 commits pushed to the master branch:

• 859ca75: 8300862: Remove some G1 collection set remembered set debugging code
• 048705c: 8300910: Remove metaprogramming/integralConstant.hpp
• 544c16e: 8300266: Detect Virtualization on Linux aarch64
• 57f2d48: 8300863: Remove C-style array declarations in java.io
• 2292ce1: 8294677: chunklevel::MAX_CHUNK_WORD_SIZE too small for some applications
• 6dd8723: 8290918: Initial nroff manpage generation for JDK 21
• b3822f5: 8300589: Use @snippet and @linkplain in java.text.CollationKey and java.text.CompactNumberFormat
• afd5921: 8298610: Refactor archiving of ConstantPool::resolved_references()
• 937ba1c: 8300111: Add rpath for common lib locations for jpackageapplauncher
• 2da2e5a: 8300946: Add sun/security/provider/certpath/OCSP/OCSPNoContentLength to ProblemList
• ... and 17 more: https://git.openjdk.org/jdk/compare/5a4945c0d95423d0ab07762c915e9cb4d3c66abb...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tschatzl Pushed as commit 3be5758.

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