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8277654: Shenandoah: Don't produce new memory state in C2 LRB runtime call #6526

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rkennke
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@rkennke rkennke commented Nov 23, 2021

The runtime call in expanded Shenandoah LRB doesn't need to produce (and consume) raw memory state. I believe this is a left-over from when the LRB (or WB) allocated from TLABs, and would mess with TLAB pointers, when not ordered correctly. (Also, we used to require ordering with RBs back when we had them, but we already removed that memory dependency on -8 offset)

Testing:

  • hotspot_gc_shenandoah
  • specjvm -XX:+UseShenandoahGC
  • tier1
  • tier2
  • tier3

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

Issue

  • JDK-8277654: Shenandoah: Don't produce new memory state in C2 LRB runtime call

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Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6526/head:pull/6526
$ git checkout pull/6526

Update a local copy of the PR:
$ git checkout pull/6526
$ git pull https://git.openjdk.java.net/jdk pull/6526/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 6526

View PR using the GUI difftool:
$ git pr show -t 6526

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6526.diff

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@bridgekeeper bridgekeeper bot commented Nov 23, 2021

👋 Welcome back rkennke! 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.

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@openjdk openjdk bot commented Nov 23, 2021

@rkennke The following labels will be automatically applied to this pull request:

  • hotspot-gc
  • shenandoah

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added hotspot-gc shenandoah labels Nov 23, 2021
@rkennke rkennke marked this pull request as ready for review Nov 26, 2021
@openjdk openjdk bot added the rfr label Nov 26, 2021
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@mlbridge mlbridge bot commented Nov 26, 2021

Webrevs

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@rwestrel rwestrel left a comment

Looks good to me.

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@openjdk openjdk bot commented Nov 26, 2021

@rkennke 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:

8277654: Shenandoah: Don't produce new memory state in C2 LRB runtime call

Reviewed-by: roland, shade

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 80 new commits pushed to 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.

@openjdk openjdk bot added the ready label Nov 26, 2021
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@shipilev shipilev left a comment

Looks okay. Does it affect performance in any way?

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@rkennke rkennke commented Nov 29, 2021

Looks okay. Does it affect performance in any way?

I couldn't see any benefits or regressions in specjvm.

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@rkennke rkennke commented Nov 29, 2021

/integrate

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@openjdk openjdk bot commented Nov 29, 2021

Going to push as commit 3d39f09.
Since your change was applied there have been 80 commits pushed to the master branch:

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot closed this Nov 29, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels Nov 29, 2021
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@openjdk openjdk bot commented Nov 29, 2021

@rkennke Pushed as commit 3d39f09.

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

@rkennke rkennke deleted the JDK-8277654 branch Nov 29, 2021
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