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8350483: AArch64: turn on signum intrinsics by default on Ampere CPUs
Backport the commit to set -XX:+UseSignumIntrinsic by default for Ampere CPUs. It is to fix performance problem observed on JMH cases vm.compiler.Signum|java.lang.*MathBench.sig[nN]um*. For example, vm.compiler.Signum._1_signumFloatTest thrpt score becomes 30x better on both jdk mainline and jdk17u-dev. The backporting can be very safe as it is limited to Ampere CPUs only and well verified on Ampere-1A with related jmh and jtreg tier1 tests.
Progress
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Issue
- JDK-8350483: AArch64: turn on signum intrinsics by default on Ampere CPUs (Enhancement - P4)
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@cnqpzhang This change now passes all automated pre-integration checks.
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8350483: AArch64: turn on signum intrinsics by default on Ampere CPUs
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- 95fe05a32508fc2ac2eb235a236111e6b9a4eba7: 8136895: Writer not closed with disk full error, file resource leaked
- f7492dda384b814c5fceaea15a2fdf1a2a7bc617: 8312475: org.jline.util.PumpReader signed byte problem
- 4241313127be05704eeebcc6454120742cc93753: 8354941: Build failure with glibc 2.42 due to uabs() name collision
- ... and 310 more: https://git.openjdk.org/jdk17u-dev/compare/fd353e38a820eed00b1a5f28e892a4d6baa3f1d1...master
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⚠️ @cnqpzhang This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.
/approval request Resolved a merging conflict as the auto backport covered a piece of unrelated code change on CodeEntryAlignment. Right now, the updated commit has the exact same changes as f529bf71 from the openjdk/jdk repository. The change is simple and straight-forward, the change itself is safely limited to AArch64-port Ampere CPUs only, and well verified on Ampere-1A system, can be safe for backport. Please approve, thanks.
Hi @cnqpzhang , can you please backport to 24 and 21 first? Removing the label in the meantime. Performance optimizations are not necessarily good candidates for backport to a rather old release.
Hi @cnqpzhang , can you please backport to 24 and 21 first? Removing the label in the meantime. Performance optimizations are not necessarily good candidates for backport to a rather old release.
Thanks for your comments, @GoeLin .
Sure I will request for backports to 24 and 21 firstly.
It is not just a performance optimization, in the worst cases the slowdown caused by the performance issue showed 80~100x time cost of normal cases, as such the functions at 1~2% of the expected run speed got severely impacted in a manner.
@cnqpzhang This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply add a new comment to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!
@cnqpzhang 8350483: The approval request has been cancelled successfully.
Status update: backport to 24 has been done (merged), and the operation to 21 is waiting for a dependent change, and 17 would follow up.
/approval request Should get backported to 17u for parity with 21u and 24u which have been done. Low risk and tier1 tests and other sanity checks pass on Ampere-1A systems. Initially intended as a performance optimization but later on found saving up to 80~100x performance defect in certain extreme cases. The issue severely impacted signum functions. Given that 17u is still extensively used by Java devs in practice, addressing this problem is essential to retore performance and maintain platform reliability. Thanks for approval.
Hi @cnqpzhang Thanks for backporting to 21 and 24. One question: is this a regression? Can you name the change that cause the performance regression? Or is this a true optimization.
Hi @cnqpzhang Thanks for backporting to 21 and 24. One question: is this a regression? Can you name the change that cause the performance regression? Or is this a true optimization.
Not a regression, the option was only enabled for some specific CPUs while this commit/backport extends its benefit to more.
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@cnqpzhang The pull request is being re-evaluated and the inactivity timeout has been reset.
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@cnqpzhang Your change (at version 6f75fc9cd9e186858c8fcc3b31470c0bc1b2b87b) is now ready to be sponsored by a Committer.
Hi @GoeLin , could you please help sponsor this and push? With sincere thanks.
Hi, May I ask for any committer's help to push this approved PR? It’s been in the queue for about a week. Thanks so much in advance!
Hi @cnqpzhang Can you find someone with expertise on aarch to sponsor this? It's the idea of sponsorship that a third person get's involved, if the backportee hasn't the necessary roles.
@adinn Hi Andrew could you please help sponsor this onto jdk17u-dev? Many thanks.
Going to push as commit c5f41eba4dc12fded813d7b6b302cc7a8f0b2e10.
Since your change was applied there have been 367 commits pushed to the master branch:
- a897ee8cb0602d374d6bcbe7c28bf5d38b804e8b: 8351933: Inaccurate masking of TC subfield decrement in ForkJoinPool
- 2dc6bac7bf3c39ad35b2db2c70d839130de036b9: 8328087: Automate javax/swing/JTable/TAB/TAB.java applet test
- b5f7d6427c8b81f40d17222cf33c7b70da8bd395: 8203867: Delete test java/awt/TrayIcon/DblClickActionEventTest/DblClickActionEventTest.html
- ... and 364 more: https://git.openjdk.org/jdk17u-dev/compare/fd353e38a820eed00b1a5f28e892a4d6baa3f1d1...master
Your commit was automatically rebased without conflicts.
@theRealAph @cnqpzhang Pushed as commit c5f41eba4dc12fded813d7b6b302cc7a8f0b2e10.
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