8257436: [aarch64] Regressions in ArrayCopyUnalignedDst.testByte/testChar for 65-78 bytes when UseSIMDForMemoryOps is on #1558

eastig · 2020-12-02T10:12:41Z

Copying data in range 65 - 80 bytes with

ldpq
ldpq 
ldp
stpq
stpq
stp

is faster than with

ldpq
ldpq
ldpq
stpq
stpq
stpq

when pointers involved are not properly aligned. This mostly affects byte and char arraycopy.
This patch fixes regressions of ArrayCopyUnalignedDst.testByte/testChar when UseSIMDForMemoryOps is on.
See the attached results for performance data
test_byte_results.txt
test_char_results.txt

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Issue

JDK-8257436: [aarch64] Regressions in ArrayCopyUnalignedDst.testByte/testChar for 65-78 bytes when UseSIMDForMemoryOps is on

Reviewers

Volker Simonis (@simonis - Reviewer)

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$ git fetch https://git.openjdk.java.net/jdk pull/1558/head:pull/1558
$ git checkout pull/1558

bridgekeeper · 2020-12-02T10:13:31Z

👋 Welcome back eastig! 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 · 2020-12-02T10:14:46Z

@eastig The following label will be automatically applied to this pull request:

hotspot-compiler

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 · 2020-12-02T10:18:02Z

Webrevs

03: Full - Incremental (c1f178e)
02: Full - Incremental (a9019cc4997976bf8ba8bfa1da3d562a1d869daf)
01: Full - Incremental (3d9d91953c685721c72694640654f8c954c3c602)
00: Full (16b36d365526473a3c8ba5fbb41ab1d7d609dc63)

eastig · 2020-12-02T10:46:52Z

@theRealAph could please check if it causes any issues on ThunderX 2?

Thanks,
Evgeny

theRealAph · 2020-12-02T10:56:39Z

@theRealAph could please check if it causes any issues on ThunderX 2?

Is there some script you use that generates the comparison? Otherwise it'll take some time.

eastig · 2020-12-02T11:12:41Z

@theRealAph could please check if it causes any issues on ThunderX 2?

Is there some script you use that generates the comparison? Otherwise it'll take some time.

Unfortunately, no. I have scripts that do runs. Then I pull all results in Excel.
BTW, I attached data comparing SIMD_OFF vs SIMD_ON(patch). JDK-8257436 has data showing regressions with SIMD three ldpq instructions. I'll attach data comparing SIMD_no_fix vs SIMD_fix later.

eastig · 2020-12-02T14:04:42Z

I updated the attached data. It now includes the following:

UseSIMDForMemoryOps is off.
UseSIMDForMemoryOps is on.
UseSIMDForMemoryOps + fix is on.

The fix is narrowed to be used for byte and char arraycopies. They have the most problems with unaligned accesses. Int arraycopies are at least 4 byte aligned. Long arraycopies are always 8 byte aligned.

mlbridge · 2020-12-02T15:21:57Z

Mailing list message from Andrew Haley on hotspot-compiler-dev:

On 02/12/2020 11:14, Evgeny Astigeevich wrote:

On Wed, 2 Dec 2020 10:56:39 GMT, Andrew Haley <aph at openjdk.org> wrote:

@theRealAph could please check if it causes any issues on ThunderX 2?

Is there some script you use that generates the comparison? Otherwise it'll take some time.

Unfortunately, no. I have scripts that do runs. Then I pull all results in Excel.

Given the nature of the change, I don't expect to see regressions on
other hardware, so I don't think it's worth doing more testing.

--
Andrew Haley (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671

eastig · 2020-12-02T18:26:32Z

I am attaching performance data for int arraycopy to show the impact of the patch on it:
test_int_results.txt

simonis

Hi Evegeny,

thanks for fixing this. Your change looks good to me. Thanks especially for measuring all the different cases.

I only have two minor request regarding the comments. Once fixed I'll sponsor this change.

Best regards,
Volker

src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp

…Char for 65-78 bytes when UseSIMDForMemoryOps is on On Graviton 2 ArrayCopyUnaligned of data range 65 - 78 bytes with the sequence of 'ldpq,ldpq,ldp,stpq,stpq,stp' is faster than with the sequence of 'ldpq,ldpq,ldpq,stpq,stpq,stpq'.

simonis

Looks good now. Thanks!

openjdk · 2020-12-03T14:03:59Z

@eastig 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:

8257436: [aarch64] Regressions in ArrayCopyUnalignedDst.testByte/testChar for 65-78 bytes when UseSIMDForMemoryOps is on

Reviewed-by: simonis

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 51 new commits pushed to the master branch:

fa58671: 8257020: [JVMCI] enable a JVMCICompiler to specify which GCs it supports
129c377: 8257594: C2 compiled checkcast of non-null object triggers endless deoptimization/recompilation cycle
e4497c9: 8256718: Obsolete the long term deprecated and aliased Trace flags
4a267f1: 8244847: Linux/PPC: runtime/CompressedOops/CompressedClassPointers: smallHeapTest fails
b44a329: 8256864: [windows] Improve tracing for mapping errors
ae1eb28: 8257604: JNI_ArgumentPusherVaArg leaks valist
4169d96: 8257143: Enable JVMCI code installation tests on AArch64
a5a034b: 8257617: TestLinkPlatform fails with new Java source version
d80ae05: 8166596: TLS support for the EdDSA signature algorithm
3932527: 8257466: Improve enum iteration
... and 41 more: https://git.openjdk.java.net/jdk/compare/60f2ba9a24416fc8d5f290c01cc8b2531f3b5ca8...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@simonis) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

eastig · 2020-12-03T14:04:23Z

/integrate

openjdk · 2020-12-03T14:05:10Z

@eastig
Your change (at version c1f178e) is now ready to be sponsored by a Committer.

simonis · 2020-12-03T15:55:02Z

/sponsor

openjdk · 2020-12-03T15:55:49Z

@simonis @eastig Since your change was applied there have been 53 commits pushed to the master branch:

b170c83: 8257591: Remove suppression of record preview related warnings in java.lang
66a2e70: 8255845: Memory leak in imageFile.cpp
fa58671: 8257020: [JVMCI] enable a JVMCICompiler to specify which GCs it supports
129c377: 8257594: C2 compiled checkcast of non-null object triggers endless deoptimization/recompilation cycle
e4497c9: 8256718: Obsolete the long term deprecated and aliased Trace flags
4a267f1: 8244847: Linux/PPC: runtime/CompressedOops/CompressedClassPointers: smallHeapTest fails
b44a329: 8256864: [windows] Improve tracing for mapping errors
ae1eb28: 8257604: JNI_ArgumentPusherVaArg leaks valist
4169d96: 8257143: Enable JVMCI code installation tests on AArch64
a5a034b: 8257617: TestLinkPlatform fails with new Java source version
... and 43 more: https://git.openjdk.java.net/jdk/compare/60f2ba9a24416fc8d5f290c01cc8b2531f3b5ca8...master

Your commit was automatically rebased without conflicts.

Pushed as commit e836396.

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

openjdk bot added the rfr Pull request is ready for review label Dec 2, 2020

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Dec 2, 2020

eastig force-pushed the JDK-8257436 branch 2 times, most recently from b7bd38d to 3d9d919 Compare December 2, 2020 13:58

eastig force-pushed the JDK-8257436 branch from 3d9d919 to a9019cc Compare December 2, 2020 14:53

simonis suggested changes Dec 3, 2020

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src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp Outdated Show resolved Hide resolved

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eastig force-pushed the JDK-8257436 branch from a9019cc to c1f178e Compare December 3, 2020 13:53

simonis approved these changes Dec 3, 2020

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openjdk bot added the ready Pull request is ready to be integrated label Dec 3, 2020

openjdk bot added the sponsor Pull request is ready to be sponsored label Dec 3, 2020

openjdk bot closed this Dec 3, 2020

openjdk bot added integrated Pull request has been integrated and removed sponsor Pull request is ready to be sponsored ready Pull request is ready to be integrated rfr Pull request is ready for review labels Dec 3, 2020

eastig deleted the JDK-8257436 branch December 17, 2020 21:16

8257436: [aarch64] Regressions in ArrayCopyUnalignedDst.testByte/testChar for 65-78 bytes when UseSIMDForMemoryOps is on #1558

8257436: [aarch64] Regressions in ArrayCopyUnalignedDst.testByte/testChar for 65-78 bytes when UseSIMDForMemoryOps is on #1558

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