8290357: Drop HeapRegion::marked_bytes() #9511

tschatzl · 2022-07-15T11:06:27Z

Hi all,

please review this removal of the HeapRegion::_marked_bytes member that records the bytes marked below tams in the recent mark as it is not really interesting in the removed places. I added comments to give reasons for this removal in the particular places for your review.

Testing: jtreg gc/g1, gha

Thanks,
Thomas

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Issue

JDK-8290357: Drop HeapRegion::marked_bytes()

Reviewers

Sangheon Kim (@sangheon - Reviewer) ⚠️ Review applies to 9d7f95bb
Ivan Walulya (@walulyai - Reviewer)

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/9511/head:pull/9511
$ git checkout pull/9511

Update a local copy of the PR:
$ git checkout pull/9511
$ git pull https://git.openjdk.org/jdk pull/9511/head

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Checkout this PR locally:
$ git pr checkout 9511

View PR using the GUI difftool:
$ git pr show -t 9511

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Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/9511.diff

tschatzl · 2022-07-15T11:07:14Z

src/hotspot/share/gc/g1/g1ConcurrentRebuildAndScrub.cpp

-    void assert_marked_words(HeapRegion* hr) {
-      assert((_marked_words * HeapWordSize) == hr->marked_bytes(),


This use is for verification/debugging only and has been suggested to remove (the _marked_words member) here during review of the single bitmap change.

bridgekeeper · 2022-07-15T11:07:51Z

👋 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.

tschatzl · 2022-07-15T11:08:27Z

src/hotspot/share/gc/g1/g1RemSetTrackingPolicy.cpp

                                  total_live_bytes,
                                  BOOL_TO_STR(selected_for_rebuild),
                                  live_bytes,
-                                  r->marked_bytes(),


At this point (scrubbing start) marked_bytes() contain the amount of marked bytes in the previous marking. This is not particularly interesting to see; live_bytes contains the current marked bytes below tams and is printed.

tschatzl · 2022-07-15T11:09:11Z

src/hotspot/share/gc/g1/g1YoungGCPostEvacuateTasks.cpp

  }

  void account_failed_region(HeapRegion* r) {
-    size_t used_words = r->marked_bytes() / HeapWordSize;


At this point, for evacuation failure regions, marked_bytes() == live_bytes() so it can be replaced without any change.

tschatzl · 2022-07-15T11:10:37Z

src/hotspot/share/prims/whitebox.cpp


  bool do_heap_region(HeapRegion* r) {
    if (r->is_old()) {
-      size_t prev_live = r->marked_bytes();


I do not think this has ever been intended (this is the marked bytes below TAMS, not including bytes between TAMS and top()), and for a lower estimate of amount of bytes reclaimed, live_bytes() is as good or better.

openjdk · 2022-07-15T11:11:10Z

@tschatzl 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.

mlbridge · 2022-07-15T11:15:37Z

Webrevs

sangheon · 2022-08-02T17:22:15Z

src/hotspot/share/gc/g1/heapRegion.cpp

 void HeapRegion::note_self_forwarding_removal_start(bool during_concurrent_start,
                                                    bool during_conc_mark) {
  // We always scrub the region to make sure the entire region is
  // parsable after the self-forwarding point removal, and update _marked_bytes


Need an update with the comment related to _marked_bytes.

sangheon

Looks good.
Just minor nit regarding the remaining comment of _marked_bytes.

openjdk · 2022-08-02T17:31:31Z

@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/8290357-remove-marked-bytes
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

openjdk · 2022-08-03T09:44:16Z

@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:

8290357: Drop HeapRegion::marked_bytes()

Reviewed-by: sangheki, 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 62 new commits pushed to the master branch:

7676be8: 8291037: Move PLAB resizing mechanism to G1EvacStats
861cc67: 8291897: TerminatingThreadLocal(s) not registered from virtual thread(s)
8d88be2: 8291459: JVM crash with GenerateOopMap::error_work(char const*, __va_list_tag*)
8a804f6: 8291454: Missing check for JLI C runtime library in CoreLibraries.gmk
5a539e8: 8291893: riscv: remove fence.i used in user space
b2f0cbd: 8064787: [macosx] In Nimbus LaF, Ctrl+Alt mnemonic doesn't work
891df21: 8259687: JTabbedPane.setComponentAt doesn't hide previously visible tab component
d4fb91b: 8291956: Simplify the loop condition in sun.net.httpserver.Request constructor
20123ea: 8291901: IGV: Preference menu disappears after JDK-8288750
8e2c006: 8291957: Redundant import statements in sun.security.ec
... and 52 more: https://git.openjdk.org/jdk/compare/0971d3464609bf4124df460ea73ff761d7e0f7b2...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.

walulyai

Lgtm!

tschatzl · 2022-08-08T13:27:27Z

Thanks @sangheon @walulyai for your reviews
/integrate

openjdk · 2022-08-08T13:29:00Z

Going to push as commit 4591937.
Since your change was applied there have been 62 commits pushed to the master branch:

7676be8: 8291037: Move PLAB resizing mechanism to G1EvacStats
861cc67: 8291897: TerminatingThreadLocal(s) not registered from virtual thread(s)
8d88be2: 8291459: JVM crash with GenerateOopMap::error_work(char const*, __va_list_tag*)
8a804f6: 8291454: Missing check for JLI C runtime library in CoreLibraries.gmk
5a539e8: 8291893: riscv: remove fence.i used in user space
b2f0cbd: 8064787: [macosx] In Nimbus LaF, Ctrl+Alt mnemonic doesn't work
891df21: 8259687: JTabbedPane.setComponentAt doesn't hide previously visible tab component
d4fb91b: 8291956: Simplify the loop condition in sun.net.httpserver.Request constructor
20123ea: 8291901: IGV: Preference menu disappears after JDK-8288750
8e2c006: 8291957: Redundant import statements in sun.security.ec
... and 52 more: https://git.openjdk.org/jdk/compare/0971d3464609bf4124df460ea73ff761d7e0f7b2...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-08-08T13:29:23Z

@tschatzl Pushed as commit 4591937.

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

initial version, use live_bytes instead of marked_bytes

9d7f95b

tschatzl commented Jul 15, 2022

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openjdk bot changed the title ~~8290357~~ 8290357: Drop HeapRegion::marked_bytes() Jul 15, 2022

tschatzl commented Jul 15, 2022

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openjdk bot added the rfr Pull request is ready for review label Jul 15, 2022

openjdk bot added the hotspot hotspot-dev@openjdk.org label Jul 15, 2022

sangheon reviewed Aug 2, 2022

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sangheon approved these changes Aug 2, 2022

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openjdk bot added the merge-conflict Pull request has merge conflict with target branch label Aug 2, 2022

tschatzl added 2 commits August 2, 2022 19:56

Remove actual member and references

f1c5bc5

Merge branch 'master' into 8290357-remove-marked-bytes

8a358fb

openjdk bot added ready Pull request is ready to be integrated and removed merge-conflict Pull request has merge conflict with target branch labels Aug 3, 2022

walulyai approved these changes Aug 8, 2022

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openjdk bot added the integrated Pull request has been integrated label Aug 8, 2022

openjdk bot closed this Aug 8, 2022

openjdk bot removed the ready Pull request is ready to be integrated label Aug 8, 2022

tschatzl deleted the submit/8290357-remove-marked-bytes branch August 8, 2022 13:29

openjdk bot removed the rfr Pull request is ready for review label Aug 8, 2022

tschatzl mentioned this pull request Sep 13, 2022

8256265: G1: Improve parallelism in regions that failed evacuation #9980

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3 tasks

		void assert_marked_words(HeapRegion* hr) {
		assert((_marked_words * HeapWordSize) == hr->marked_bytes(),

8290357: Drop HeapRegion::marked_bytes() #9511

8290357: Drop HeapRegion::marked_bytes() #9511

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