8295069: [PPC64] Performance regression after JDK-8290025

[TheRealMDoerr]

I have a proposal to mitigate the performance regression (see JBS issue) on PPC64 significantly. We get most of the performance back. Please review. Implemented like on aarch64, now. Also use 64 bit load for uint64_t _nmethod_disarm_value (not relevant for Little Endian).

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Progress

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Issue

• JDK-8295069: [PPC64] Performance regression after JDK-8290025

Reviewers

• Richard Reingruber (@reinrich - Reviewer)
• Lutz Schmidt (@RealLucy - Reviewer)

Reviewing

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[TheRealMDoerr]

/label add gc

[TheRealMDoerr]

/label add runtime

[openjdk]

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[openjdk]

@TheRealMDoerr
The label runtime is not a valid label.
These labels are valid:

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• hotspot-compiler
• ide-support
• kulla
• i18n
• shenandoah
• jdk
• javadoc
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• hotspot-runtime
• jmx
• build
• nio
• client
• core-libs
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[TheRealMDoerr]

/label add hotspot-gc

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[TheRealMDoerr]

/label add hotspot-runtime

[mlbridge]

Webrevs

• 03: Full - Incremental (08b86237)
• 02: Full - Incremental (d9ea8790)
• 01: Full - Incremental (99d133ba)
• 00: Full (7c19cb17)

[openjdk]

@TheRealMDoerr
The hotspot-gc label was successfully added.

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@TheRealMDoerr
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[TheRealMDoerr]

Changed to draft. Aarch64 seems to have a better solution. I should probably implement it the same way.

[nick-arm]

This was fixed for AArch64 in JDK-8290700 - maybe it's worth adopting the NMethodPatchingType enum used there?

[TheRealMDoerr]

Thanks for the hint! We had already noticed and I was working on it in the meantime.

[TheRealMDoerr]

Note: conc_instruction_and_data_patch is for generational ZGC which is not yet in jdk master. PPC64 implementation will still work if we forget to update from conc_data_patch.

[theRealAph]

Might it make sense for PPC to do what AArch64 does? We don't need any memory fence instructions on the fast path.

[TheRealMDoerr]

Might it make sense for PPC to do what AArch64 does? We don't need any memory fence instructions on the fast path.

We are actually doing what AArch64 does, now. AArch64 still uses membar(__ LoadLoad) for (non-generational) ZGC and ShenandoahGC, because they use NMethodPatchingType::conc_data_patch. Other GCs don't need any memory fence instructions. (See BarrierSetAssembler::nmethod_entry_barrier.) Exactly like on PPC64, now.
Note that the patching epoch implementation is protected by NMethodPatchingType::conc_instruction_and_data_patch and is hence not used at all in jdk master. (Only in generational ZGC which is not yet integrated into jdk master.)

It may make sense to implement the patching epoch code on PPC64 as well. We could evaluate it, but we should better do that with generational ZGC (like on AArch64).

[theRealAph]

Might it make sense for PPC to do what AArch64 does? We don't need any memory fence instructions on the fast path.

We are actually doing what AArch64 does, now. AArch64 still uses membar(__ LoadLoad) for (non-generational) ZGC and ShenandoahGC, because they use NMethodPatchingType::conc_data_patch. Other GCs don't need any memory fence instructions.

Ah, okay. On AArch64 we only issue a LoadLoad for conc_data_patch so I think we're good.

[reinrich]

Changes look good!
Thanks, Richard.

[openjdk]

@TheRealMDoerr 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:

8295069: [PPC64] Performance regression after JDK-8290025

Reviewed-by: rrich, lucy

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 16 new commits pushed to the master branch:

• 9d0009e: 6777156: GTK L&F: JFileChooser can jump beyond root directory in combobox and selection textarea.
• 3ebe5ad: 8294751: Zero: Allow larger default heaps
• 33d0618: 6616245: NullPointerException when using JFileChooser with a custom FileView
• fba763f: 8291519: jdk/jfr/api/event/TestShouldCommit.java failed with Unexpected value of shouldCommit()
• 6053bf0: 8293782: Shenandoah: some tests failed on lock rank check
• 4435d56: 8282395: URL.openConnection can throw IOOBE
• fe70487: 8294958: java/net/httpclient/ConnectTimeout tests are slow
• 97f1321: 8294356: IGV: scheduled graphs contain duplicated elements
• 5e05e42: 8294901: remove pre-VS2017 checks in Windows related coding
• e775acf: 8293986: Incorrect double-checked locking in com.sun.beans.introspect.ClassInfo
• ... and 6 more: https://git.openjdk.org/jdk/compare/4df4a1f8e238ebf49d4b0e1e102ccdc3cdb82de9...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.

[TheRealMDoerr]

Thanks for reviewing!
Note: I have tested the new code on Big Endian linux as well. My latest commit avoids hitting the C++ barrier code unnecessarily often.

[RealLucy]

Changes look good to me.

[TheRealMDoerr]

Thanks for the review!

[TheRealMDoerr]

/integrate

[openjdk]

Going to push as commit 945950d.
Since your change was applied there have been 22 commits pushed to the master branch:

• d362e16: 8294689: The SA transported_core.html file needs quite a bit of work
• 07946aa: 8289552: Make intrinsic conversions between bit representations of half precision values and floats
• 2586b1a: 8295155: Incorrect javadoc of java.base module
• e1a77cf: 8295163: Remove old hsdis Makefile
• 3c7ae12: 8294821: Class load improvement for AES crypto engine
• 619cd82: 8294702: BufferedInputStream uses undefined value range for markpos
• 9d0009e: 6777156: GTK L&F: JFileChooser can jump beyond root directory in combobox and selection textarea.
• 3ebe5ad: 8294751: Zero: Allow larger default heaps
• 33d0618: 6616245: NullPointerException when using JFileChooser with a custom FileView
• fba763f: 8291519: jdk/jfr/api/event/TestShouldCommit.java failed with Unexpected value of shouldCommit()
• ... and 12 more: https://git.openjdk.org/jdk/compare/4df4a1f8e238ebf49d4b0e1e102ccdc3cdb82de9...master

Your commit was automatically rebased without conflicts.

[openjdk]

@TheRealMDoerr Pushed as commit 945950d.

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