8371720: G1: G1MergeHeapRootsTask::G1ClearBitmapClosure unnecessarily clears marking related data structures

[tschatzl]

Hi all,

please review this change that removes resetting concurrent mark state from G1ClearBitmapClosure that is responsible for clearing the bitmaps for regions in the collection set.

It is unnecessary to clear concurrent mark state in there. All the regions processed here are regions in the collection set, and they are by definition completely excluded from concurrent mark activity. Also see which regions G1ConcurrentMark::pre_concurrent_start() includes or rather excludes.

Testing: tier1-5. gha

Thanks,
Thomas

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Integration blocker

 ⚠️ Failed to retrieve information on issue 8371720. Please make sure it exists and is accessible.

Issue

• ⚠️ Failed to retrieve information on issue 8371720.

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/28353/head:pull/28353
$ git checkout pull/28353

Update a local copy of the PR:
$ git checkout pull/28353
$ git pull https://git.openjdk.org/jdk.git pull/28353/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 28353

View PR using the GUI difftool:
$ git pr show -t 28353

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/28353.diff

[bridgekeeper]

👋 Welcome back tschatzl! 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]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@tschatzl 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.