8324304: RISC-V: add hw probe flags #17519

Hamlin-Li · 2024-01-22T15:10:53Z

Hi,
Can you help to review this simple patch to add hw probe flags?
Thanks!

Per https://github.com/torvalds/linux/blob/master/arch/riscv/include/uapi/asm/hwprobe.h, several extensions were already added in kernel code, we have several intrinsics or funtionalities depends on these extension, it's ready to add these hw probe flags already used in jdk into jdk code.

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Issue

JDK-8324304: RISC-V: add hw probe flags (Enhancement - P4)

Reviewers

Fei Yang (@RealFYang - Reviewer)
Robbin Ehn (@robehn - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/17519/head:pull/17519
$ git checkout pull/17519

Update a local copy of the PR:
$ git checkout pull/17519
$ git pull https://git.openjdk.org/jdk.git pull/17519/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 17519

View PR using the GUI difftool:
$ git pr show -t 17519

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/17519.diff

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bridgekeeper · 2024-01-22T15:12:34Z

👋 Welcome back mli! 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 · 2024-01-22T15:14:12Z

@Hamlin-Li The following label will be automatically applied to this pull request:

hotspot-runtime

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 · 2024-01-22T15:16:32Z

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RealFYang

LGTM. Any test performed?
BTW: Seems that probe for option UseZvkn could also be added which consists of Zvkned, Zvknhb, Zvkb and Zvkt. I see these are also there in https://github.com/torvalds/linux/blob/master/arch/riscv/include/uapi/asm/hwprobe.h.

openjdk · 2024-01-23T04:27:22Z

@Hamlin-Li 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:

8324304: RISC-V: add hw probe flags

Reviewed-by: fyang, rehn

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 60 new commits pushed to the master branch:

65d6bc1: 8324765: C2 SuperWord: remove dead code: SuperWord::insert_extracts
525c0cd: 8324752: C2 Superword: remove SuperWordRTDepCheck
2e748c9: 8175386: Clarify exception behavior of Types utility methods
70f4a4e: 8324786: validate-source fails after JDK-8042981
ed3272c: 8042981: Strip type annotations in Types' utility methods
6d18562: 8324785: ProblemList two tests on linux due to JDK-8315923
91d8ea7: 8323835: Updating ASM to 9.6 for JDK 23
a65a895: 8315923: pretouch_memory by atomic-add-0 fragments huge pages unexpectedly
62b3293: 8324241: Always record evol_method deps to avoid excessive method flushing
885e9b7: 8324722: Serial: Inline block_is_obj of subclasses of Generation
... and 50 more: https://git.openjdk.org/jdk/compare/c9cacfb25d1f15c879c961d2965a63c9fe4d9fa7...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.

RealFYang · 2024-01-23T10:47:15Z

PS: I just realized that this will auto-enable experimental RV-specific JVM options like UseZtso, UseZacas, etc. if the features are available, something which I think we shouldn't do for now. These experimental options are not fully tested on real hardwares yet. Maybe remove UPDATE_DEFAULT(UseZtso), UPDATE_DEFAULT(UseZtso) from ext_Ztso, ext_Zacas declarations at the same time? Or postpone this change for some time until we have the hardware?

Hamlin-Li · 2024-01-23T11:57:39Z

I just tested on Lichee Pi 4A, seems the default behaviour is to disable them.

echo "enable explicitly ......"
TEST_OPTIONS="-XX:+UseZicboz -XX:+UseZtso -XX:+UseZacas -XX:+UseZfh"
$J_H/bin/java -XX:+PrintFlagsFinal -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions ${TEST_OPTIONS} -version | grep -e UseZicboz -e UseZtso -e UseZacas -e UseZfh

echo "by default ......"
TEST_OPTIONS=""
$J_H/bin/java -XX:+PrintFlagsFinal -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions ${TEST_OPTIONS} -version | grep -e UseZicboz -e UseZtso -e UseZacas -e UseZfh

output is as below:

enable explicitly ......
     bool UseZacas                                 = true                            {ARCH experimental} {command line}
     bool UseZfh                                   = true                                 {ARCH product} {command line}
     bool UseZicboz                                = true                            {ARCH experimental} {command line}
     bool UseZtso                                  = true                            {ARCH experimental} {command line}
by default ......
     bool UseZacas                                 = false                           {ARCH experimental} {default}
     bool UseZfh                                   = false                                {ARCH product} {default}
     bool UseZicboz                                = false                           {ARCH experimental} {default}
     bool UseZtso                                  = false                           {ARCH experimental} {default}

Hamlin-Li · 2024-01-23T13:44:07Z

LGTM. Any test performed? BTW: Seems that probe for option UseZvkn could also be added which consists of Zvkned, Zvknhb, Zvkb and Zvkt. I see these are also there in https://github.com/torvalds/linux/blob/master/arch/riscv/include/uapi/asm/hwprobe.h.

Yes, I tested test/hotspot/jtreg/compiler/ via qemu, no failures related to this options are found.
The reason other flags are not added is that we don't have them in jdk yet.

RealFYang · 2024-01-24T01:01:41Z

I just tested on Lichee Pi 4A, seems the default behaviour is to disable them.

echo "enable explicitly ......"
TEST_OPTIONS="-XX:+UseZicboz -XX:+UseZtso -XX:+UseZacas -XX:+UseZfh"
$J_H/bin/java -XX:+PrintFlagsFinal -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions ${TEST_OPTIONS} -version | grep -e UseZicboz -e UseZtso -e UseZacas -e UseZfh

echo "by default ......"
TEST_OPTIONS=""
$J_H/bin/java -XX:+PrintFlagsFinal -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions ${TEST_OPTIONS} -version | grep -e UseZicboz -e UseZtso -e UseZacas -e UseZfh

output is as below:

enable explicitly ......
     bool UseZacas                                 = true                            {ARCH experimental} {command line}
     bool UseZfh                                   = true                                 {ARCH product} {command line}
     bool UseZicboz                                = true                            {ARCH experimental} {command line}
     bool UseZtso                                  = true                            {ARCH experimental} {command line}
by default ......
     bool UseZacas                                 = false                           {ARCH experimental} {default}
     bool UseZfh                                   = false                                {ARCH product} {default}
     bool UseZicboz                                = false                           {ARCH experimental} {default}
     bool UseZtso                                  = false                           {ARCH experimental} {default}

Say, when you are running some latest kernel with the hwprobe capability on some new RISC-V hardwares with those extensions.
Then these JVM options will be auto-enabled, right? But I think we need some time to manually enable and fully test them (especially, -XX:+UseZtso and -XX:+UseZacas) before that happens. AFAIK, Lichee Pi 4A is not equipped with those extensions and is running some older kernel.

Hamlin-Li · 2024-01-24T11:02:27Z

It makes sense, removed UPDATE_DEFAULT for these extensions.

RealFYang · 2024-01-25T08:13:57Z

It makes sense, removed UPDATE_DEFAULT for these extensions.

Thanks for the update. Would you mind one more tweak? I think we should also remove the auto-enablement of UseZic64b, UseZicbom, UseZicbop and UseZihintpause which are also experimental options for now.

Hamlin-Li · 2024-01-25T19:12:16Z

I'm not sure, as these vm options (UseZic64b, UseZicbom, UseZicbop and UseZihintpause) are not enabled in RiscvHwprobe::add_features_from_query_result(), so I think they are not enabled automatically even if the hw supports these features, unless a vendor want to enable them.

So, I think it's good to keep auto-enablement of Zicboz/Ztso/Zacas in vm_version_riscv.hpp, and remove the enable code of these options in RiscvHwprobe::add_features_from_query_result() in this patch?

RealFYang · 2024-01-26T09:42:54Z

I'm not sure, as these vm options (UseZic64b, UseZicbom, UseZicbop and UseZihintpause) are not enabled in RiscvHwprobe::add_features_from_query_result(), so I think they are not enabled automatically even if the hw supports these features, unless a vendor want to enable them.

Sorry, I missed that before. I think you are right.

So, I think it's good to keep auto-enablement of Zicboz/Ztso/Zacas in vm_version_riscv.hpp, and remove the enable code of these options in RiscvHwprobe::add_features_from_query_result() in this patch?

Yeah, that will be more consistent.

Hamlin-Li · 2024-01-28T09:25:40Z

Updated, please take a look again.

RealFYang

Thanks.

robehn

Seems alright, thanks!

Hamlin-Li · 2024-01-29T09:16:03Z

Thanks @RealFYang @robehn for your reviewing.

/integrate

openjdk · 2024-01-29T09:17:47Z

Going to push as commit b39b876.
Since your change was applied there have been 67 commits pushed to the master branch:

69586e7: 8322996: BoxLockNode creation fails with assert(reg < CHUNK_SIZE) failed: sanity
f0bae79: 8324750: C2: rename Matcher methods using "superword" -> "autovectorization"
6ad78ca: 8324775: C2 SuperWord: refactor visited sets
422020c: 8210858: AArch64: remove Math.log intrinsic
0d5f5e1: 8322484: 22-b26 Regression in J2dBench-bimg_misc-G1 (and more) on Windows-x64 and macOS-x64
af9cd97: 8324800: gcc windows build broken after 8322757
8950d68: 8324753: [AIX] adjust os_posix after JDK-8318696
65d6bc1: 8324765: C2 SuperWord: remove dead code: SuperWord::insert_extracts
525c0cd: 8324752: C2 Superword: remove SuperWordRTDepCheck
2e748c9: 8175386: Clarify exception behavior of Types utility methods
... and 57 more: https://git.openjdk.org/jdk/compare/c9cacfb25d1f15c879c961d2965a63c9fe4d9fa7...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-01-29T09:17:54Z

@Hamlin-Li Pushed as commit b39b876.

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

Initial commit

27cf282

openjdk bot added the rfr Pull request is ready for review label Jan 22, 2024

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Jan 22, 2024

RealFYang approved these changes Jan 23, 2024

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openjdk bot added the ready Pull request is ready to be integrated label Jan 23, 2024

remove UPDATE_DEFAULT

d5c7746

Hamlin-Li added 2 commits January 28, 2024 09:15

revert some changes

d36002e

add flags only without enablement

731e86f

RealFYang approved these changes Jan 29, 2024

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robehn approved these changes Jan 29, 2024

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openjdk bot added the integrated Pull request has been integrated label Jan 29, 2024

openjdk bot closed this Jan 29, 2024

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jan 29, 2024

Hamlin-Li deleted the hw-probe-code branch January 29, 2024 15:15

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