8325821: [REDO] use "dmb.ishst+dmb.ishld" for release barrier

[kuaiwei]

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he origin patch for https://bugs.openjdk.org/browse/JDK-8324186 has 2 issues: 1 It show regression in some platform, like Apple silicon in mac os 2 Can not handle instruction sequence like "dmb.ishld; dmb.ishst; dmb.ishld; dmb.ishld"

It can be fixed by: 1 Enable AlwaysMergeDMB by default, only disable it in architecture we can see performance improvement (N1 or N2) 2 Check the special pattern and merge the subsequent dmb.

It also fix a bug when code buffer is expanding, st/ld/dmb can not be merged. I added unit tests for these.

This patch still has a unhandled case. Insts like "dmb.ishld; dmb.ishst; dmb.ish", it will merge the last 2 instructions and can not merge all three. Because when emitting dmb.ish, if merge all previous dmbs, the code buffer will shrink the size. I think it may break some resumption and think it's not a common pattern.

In previous PR https://github.com/openjdk/jdk/pull/18467 , I tried an implementation to use state machine for merging. But it looks risky to pending instruction during emitting.

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Issue

• JDK-8325821: [REDO] use "dmb.ishst+dmb.ishld" for release barrier (Enhancement - P4)

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[bridgekeeper[bot]]

:wave: Welcome back kuaiwei! 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[bot]]

@kuaiwei 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:

8325821: [REDO] use "dmb.ishst+dmb.ishld" for release barrier

Reviewed-by: shade, aph

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 81 new commits pushed to the master branch:

• e7dc76b5776e05082281fb640d1592479cfe9e6b: 8333849: (dc) DatagramChannel send/receive fails with UOE if buffer backed by memory segment allocated from shared arena
• ec1664e8c9413890ce2dae5c2dbbce3449d67882: 8333804: java/net/httpclient/ForbiddenHeadTest.java threw an exception with 0 failures
• e22fc121aed56dad2eedfdc3a53f2a655c3b200b: 8333775: Small improvement to outputStream auto-indentation mode
• 7b43a8cd7c663facbe490f889838d7ead0eba0f9: 8333824: Unused ClassValue in VarHandles
• 5f9d3e3af8342592242cb304b2c219508d56ed3a: 8333722: Fix CompilerDirectives for non-compiler JVM variants
• 83b34410e326c47f357a37c3a337b7dedb8cbbda: 8322811: jcmd System.dump_map help info has conflicting statements
• 8aa35cacfcc94d261de102b628eb954c71eae98e: 8333833: Remove the use of ByteArrayLittleEndian from UUID::toString
• de55db2352f84c101f8197ee7aca80d72807fbc5: 8333522: JFR SwapSpace event might read wrong free swap space size
• a941397327972f130e683167a1b429f17603df46: 8329031: CPUID feature detection for Advanced Performance Extensions (Intel® APX)
• 8d2f9e57c3797c01c84df007f4d2bfdcd645d0c0: 8333749: Consolidate ConstantDesc conversion in java.base
• ... and 71 more: https://git.openjdk.org/jdk/compare/d826127970bd2ae8bf4cacc3c55634dc5af307c4...master

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[theRealAph]

This looks ready to me. I think we need jcstress with C1 and C2, and we should be done. @shipilev , do you agree?

[shipilev]

This looks ready to me. I think we need jcstress with C1 and C2, and we should be done. @shipilev , do you agree?

Yes. Just run jcstress with defaults, maybe limiting the time budget to about 24 hours, and we are done. Default configuration would work through different combinations of C1/C2 compilations for all actors, which is what we want to check for this change: that we don't mess up the barrier emitting scheme in different compilers/interpreters.

[shipilev]

Note that current jcstress run would likely fail due to JDK-8332670.

[kuaiwei]

This looks ready to me. I think we need jcstress with C1 and C2, and we should be done. @shipilev , do you agree?

Yes. Just run jcstress with defaults, maybe limiting the time budget to about 24 hours, and we are done. Default configuration would work through different combinations of C1/C2 compilations for all actors, which is what we want to check for this change: that we don't mess up the barrier emitting scheme in different compilers/interpreters.

I can run the jcstress test. I will run fastdebug build with java -jar jcstress-latest.jar -tb 24h Is it the correct command ?

[shipilev]

I can run the jcstress test. I will run fastdebug build with java -jar jcstress-latest.jar -tb 24h Is it the correct command ?

Yes, I think so.

[shipilev]

I can run the jcstress test. I will run fastdebug build with java -jar jcstress-latest.jar -tb 24h Is it the correct command > Yes, I think so.

FTR, I ran Linux AArch64 server release on Graviton 3 instance (ergonomics selects -AlwaysMergeDMB there) for 12 hours. Apart from failures from JDK-8332670, I see no other trouble. Scheduled a quick run with +AlwaysMergeDMB as well.

[kuaiwei]

I can run the jcstress test. I will run fastdebug build with java -jar jcstress-latest.jar -tb 24h Is it the correct command > Yes, I think so.

FTR, I ran Linux AArch64 server release on Graviton 3 instance (ergonomics selects -AlwaysMergeDMB there) for 12 hours. Apart from failures from JDK-8332670, I see no other trouble. Scheduled a quick run with +AlwaysMergeDMB as well.

Thanks for testing. I'm running jcstress on a neoverse-n2 instance. I got some "soft errs" in console output. Are they real error?

[shipilev]

Thanks for testing. I'm running jcstress on a neoverse-n2 instance. I got some "soft errs" in console output. Are they real error?

Soft errors are API inconsistencies that jcstress harness handled. As long as you don't have new hard errors, you are fine.

[kuaiwei]

I can run the jcstress test. I will run fastdebug build with java -jar jcstress-latest.jar -tb 24h Is it the correct command > Yes, I think so.

FTR, I ran Linux AArch64 server release on Graviton 3 instance (ergonomics selects -AlwaysMergeDMB there) for 12 hours. Apart from failures from JDK-8332670, I see no other trouble. Scheduled a quick run with +AlwaysMergeDMB as well.

Thanks for testing. I'm running jcstress on a neoverse-n2 instance. I got some "soft errs" in console output. Are they real error?

My jcstress test is done and no error is reported.

[kuaiwei]

Thanks for your review.

[kuaiwei]

/integrate

[openjdk[bot]]

@kuaiwei Your change (at version 68c3018cf25c850dab7ab725135e784fa958b140) is now ready to be sponsored by a Committer.

[kuaiwei]

@theRealAph @shipilev Could you help sponsor it ? Thanks.

[shipilev]

GH says the branch has conflicts that must be resolved. Merging from master is advisable anyway to avoid merge surprises. Let's do that before integrating.

[TobiHartmann]

Given that the first version of the patch had some issues, I would recommend waiting for the fork tomorrow and only integrating this into JDK 24.

[TobiHartmann]

I'll run this through our correctness and performance testing and report back once it passed.

[shipilev]

I'll run this through our correctness and performance testing and report back once it passed.

How was it, Tobias? Any surprises?

[TobiHartmann]

Sorry for the delay, I had to re-run a subset of the benchmarks due to high variance. All green now.

[shipilev]

Sorry for the delay, I had to re-run a subset of the benchmarks due to high variance. All green now.

Great, thanks for testing.

I think we are ready to integrate this now.

[kuaiwei]

/integrate

[openjdk[bot]]

@kuaiwei Your change (at version 0afa69325052643dbf3b0bd752d822ee062884bb) is now ready to be sponsored by a Committer.

[shipilev]

/sponsor

[openjdk[bot]]

Going to push as commit 2a242db01ed1d502affa4a954e601266fa98dfbe. Since your change was applied there have been 81 commits pushed to the master branch:

• e7dc76b5776e05082281fb640d1592479cfe9e6b: 8333849: (dc) DatagramChannel send/receive fails with UOE if buffer backed by memory segment allocated from shared arena
• ec1664e8c9413890ce2dae5c2dbbce3449d67882: 8333804: java/net/httpclient/ForbiddenHeadTest.java threw an exception with 0 failures
• e22fc121aed56dad2eedfdc3a53f2a655c3b200b: 8333775: Small improvement to outputStream auto-indentation mode
• 7b43a8cd7c663facbe490f889838d7ead0eba0f9: 8333824: Unused ClassValue in VarHandles
• 5f9d3e3af8342592242cb304b2c219508d56ed3a: 8333722: Fix CompilerDirectives for non-compiler JVM variants
• 83b34410e326c47f357a37c3a337b7dedb8cbbda: 8322811: jcmd System.dump_map help info has conflicting statements
• 8aa35cacfcc94d261de102b628eb954c71eae98e: 8333833: Remove the use of ByteArrayLittleEndian from UUID::toString
• de55db2352f84c101f8197ee7aca80d72807fbc5: 8333522: JFR SwapSpace event might read wrong free swap space size
• a941397327972f130e683167a1b429f17603df46: 8329031: CPUID feature detection for Advanced Performance Extensions (Intel® APX)
• 8d2f9e57c3797c01c84df007f4d2bfdcd645d0c0: 8333749: Consolidate ConstantDesc conversion in java.base
• ... and 71 more: https://git.openjdk.org/jdk/compare/d826127970bd2ae8bf4cacc3c55634dc5af307c4...master

Your commit was automatically rebased without conflicts.

[openjdk[bot]]

@shipilev @kuaiwei Pushed as commit 2a242db01ed1d502affa4a954e601266fa98dfbe.

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