8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds #26029

vamsi-parasa · 2025-06-27T22:13:47Z

Currently, APX is not enabled consistently between product and debug builds.

If the hardware supports Intel APX:

In product builds, APX is disabled by default, even if the user explicitly enables it using -XX:+UnlockExperimentalVMOptions -XX:+UseAPX.
In debug builds, APX is enabled by default regardless of whether the user explicitly enables it or not.

The goal of this PR is to enable APX for both product and debug builds if and only if the user explicitly enables it using -XX:+UnlockExperimentalVMOptions -XX:+UseAPX.

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Commit message must refer to an issue

Issue

JDK-8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds (Enhancement - P3)

Reviewers

Sandhya Viswanathan (@sviswa7 - Reviewer)
David Holmes (@dholmes-ora - Reviewer)
Jatin Bhateja (@jatin-bhateja - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/26029/head:pull/26029
$ git checkout pull/26029

Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk.git pull/26029/head

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$ git pr checkout 26029

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bridgekeeper · 2025-06-27T22:14:19Z

👋 Welcome back sparasa! 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 · 2025-06-27T22:14:27Z

@vamsi-parasa 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:

8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds

Reviewed-by: sviswanathan, dholmes, jbhateja

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 50 new commits pushed to the master branch:

1ac7489: 8361180: Disable CompiledDirectCall verification with -VerifyInlineCaches
055d2ff: 8361215: Add AOT test case: verification constraint classes are excluded
2bff8e0: 8360462: [macosx] row selection not working with Ctrl+Shift+Down/Up in AquaL&F
... and 47 more: https://git.openjdk.org/jdk/compare/20e0055e202e523b40e8b066e2f71c21d8cc5ea9...master

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openjdk · 2025-06-27T22:14:53Z

@vamsi-parasa The following label will be automatically applied to this pull request:

hotspot

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 · 2025-06-27T22:17:49Z

Webrevs

01: Full - Incremental (601ac00f)
00: Full (fd3f346c)

jatin-bhateja · 2025-06-28T08:03:30Z

Please change the title as "8360776: Enable -XX+UseAPX as Experiminatal feature in all builds"

We should also backport it to JDK-25 before RDP2

jatin-bhateja · 2025-06-28T08:04:59Z

src/hotspot/os_cpu/bsd_x86/os_bsd_x86.cpp

@@ -429,7 +429,7 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
      stub = VM_Version::cpuinfo_cont_addr();
    }

-#if !defined(PRODUCT) && defined(_LP64)
+#if defined(_LP64)


Is it still required after the removal of the 32-bit port of x86?

Pls see the #if defined(_LP64) check removed in the updated code.

jatin-bhateja · 2025-06-28T08:06:18Z

src/hotspot/os_cpu/linux_x86/os_linux_x86.cpp

@@ -255,7 +255,7 @@ bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
      stub = VM_Version::cpuinfo_cont_addr();
    }

-#if !defined(PRODUCT) && defined(_LP64)
+#if defined(_LP64)


Do we still need this after removal of 32-bit port of x86 ?

Pls see the #if defined(_LP64) check removed in the updated code.

jatin-bhateja · 2025-06-28T08:36:30Z

Verified patch with the following configurations, we now enable APX only on APX-capable targets with -XX:+UnlockExperimentalVMOptions

CPROMPT>sde64 -dmr -ptr_raise -- java -XX:+PrintFlagsFinal -XX:+UnlockExperimentalVMOptions -XX:-UseAPX --version | grep UseAPX
     bool UseAPX                                   = false                           {ARCH experimental} {command line}
CPROMPT>sde64 -dmr -ptr_raise -- java -XX:+PrintFlagsFinal -XX:+UnlockExperimentalVMOptions -XX:+UseAPX --version | grep UseAPX
     bool UseAPX                                   = true                            {ARCH experimental} {command line}
CPROMPT>sde64 -dmr -ptr_raise -- java -XX:+PrintFlagsFinal -XX:+UnlockExperimentalVMOptions  --version | grep UseAPX
     bool UseAPX                                   = false                           {ARCH experimental} {default}
CPROMPT>sde64 -gnr -ptr_raise -- java -XX:+PrintFlagsFinal -XX:+UnlockExperimentalVMOptions -XX:+UseAPX --version | grep UseAPX
OpenJDK 64-Bit Server VM warning: UseAPX is not supported on this CPU, setting it to false
     bool UseAPX                                   = false                           {ARCH experimental} {command line}
CPROMPT>sde64 -gnr -ptr_raise -- java -XX:+PrintFlagsFinal -XX:+UnlockExperimentalVMOptions -XX:-UseAPX --version | grep UseAPX
     bool UseAPX                                   = false                           {ARCH experimental} {command line}

dholmes-ora · 2025-06-30T06:54:42Z

src/hotspot/cpu/x86/vm_version_x86.cpp

-  // Enable APX support for product builds after
-  // completion of planned features listed in JDK-8329030.


So you have decided not to follow the original plan ( as JDK-8329030 is not complete) and instead go ahead and enable APX in product mode now. Why? Was this discussed anywhere?

@dholmes-ora The remaining items in JDK-8329030 are nice to have. I will update JDK-8329030 accordingly to reflect this.

openjdk · 2025-06-30T18:23:35Z

@vamsi-parasa Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

vamsi-parasa · 2025-06-30T18:26:01Z

Please change the title as "8360776: Enable -XX+UseAPX as Experiminatal feature in all builds"

We should also backport it to JDK-25 before RDP2

Please see the updated title as suggested.

sviswa7

Looks good to me.

dholmes-ora

Okay the changes do as described.

Thanks

jatin-bhateja

LGTM.

Best Regards,
Jatin

vamsi-parasa · 2025-07-01T19:12:06Z

Hi Emanuel (@eme64),

Would it be possible to test this PR?
Please let me know.

Thanks,
Vamsi

TobiHartmann · 2025-07-02T05:41:13Z

I submitted testing for this and will report back once it passed.

TobiHartmann · 2025-07-02T06:32:30Z

We should also backport it to JDK-25 before RDP2

Enabling APX as an experimental feature in product feels like an enhancement to me, I therefore converted this from a bug to an RFE. Per JEP 3, this would need approval for being backported to JDK 25 during RDP 1.

openjdk bot added the rfr Pull request is ready for review label Jun 27, 2025

openjdk bot added the hotspot hotspot-dev@openjdk.org label Jun 27, 2025

jatin-bhateja reviewed Jun 28, 2025

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dholmes-ora reviewed Jun 30, 2025

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8360776: Enable -XX:+UseAPX as experimental feature in all builds

601ac00

vamsi-parasa force-pushed the dis_apx branch from fd3f346 to 601ac00 Compare June 30, 2025 18:23

vamsi-parasa changed the title ~~8360776: Disable Intel APX by default and enable it only if requested by the user using -XX:+UnlockExperimentalVMOptions -XX:+UseAPX~~ 8360776: Enable -XX:+UseAPX as experimental feature in all builds Jun 30, 2025

sviswa7 approved these changes Jun 30, 2025

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Jun 30, 2025

dholmes-ora approved these changes Jul 1, 2025

View reviewed changes

jatin-bhateja approved these changes Jul 1, 2025

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vamsi-parasa changed the title ~~8360776: Enable -XX:+UseAPX as experimental feature in all builds~~ 8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds Jul 1, 2025

openjdk bot changed the title ~~8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds~~ 8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds Jul 1, 2025

openjdk bot added ready Pull request is ready to be integrated and removed ready Pull request is ready to be integrated labels Jul 1, 2025

		// Enable APX support for product builds after
		// completion of planned features listed in JDK-8329030.

8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds #26029

Are you sure you want to change the base?

8360776: Disable Intel APX by default and enable it with -XX:+UnlockExperimentalVMOptions -XX:+UseAPX in all builds #26029

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