8378177: AllowExtshm flag cleanup on AIX by april-ivy · Pull Request #30103 · openjdk/jdk

april-ivy · 2026-03-06T00:48:08Z

As discussed in #29671 & https://bugs.openjdk.org/browse/JDK-8378177, the AllowExtshm diagnostic flag, _extshm variable, and extshm() function are removed. The flag never worked because it was not parsed early enough so the VM exits before the flag is available. EXTSHM is not something we want to support.

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JDK-8378177: AllowExtshm flag cleanup on AIX (Bug - P4)

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Martin Doerr (@TheRealMDoerr - Reviewer)
Thomas Stuefe (@tstuefe - Reviewer)

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april-ivy · 2026-03-06T00:49:27Z

@TheRealMDoerr

bridgekeeper · 2026-03-06T00:49:37Z

👋 Welcome back aprilpet! 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 · 2026-03-06T00:50:37Z

@april-ivy This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8378177: AllowExtshm flag cleanup on AIX

Reviewed-by: mdoerr, stuefe

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At the time when this comment was updated there had been 34 new commits pushed to the master branch:

2fc7bdc: 8379411: Use TestFramework scenarios in 837841
5e58808: 8378744: Obsolete NewSizeThreadIncrease flag
23adf6a: 8378569: Refactor test/jdk/java/net/httpclient/http3/H3ErrorHandlingTest.java to use JUnit
... and 31 more: https://git.openjdk.org/jdk/compare/f266079d26ffc1541e5d3146258f7d39188d1a84...master

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openjdk · 2026-03-06T00:51:35Z

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

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mlbridge · 2026-03-06T00:55:17Z

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TheRealMDoerr

Thanks for working on it!

TheRealMDoerr · 2026-03-06T10:51:14Z

-      // to be a fatal error by default. On certain AIX systems, leaving EXTSHM=ON means
-      // that the VM is not able to allocate 64k pages for the heap.
-      // We do not want to run with reduced performance.
-      vm_exit_during_initialization("EXTSHM is ON. Please remove EXTSHM from your environment.");


We should keep vm_exit_during_initialization if "EXTSHM" is set, but remove the AllowExtshm check, and the log_warning above.

openjdk · 2026-03-06T16:44:33Z

@aprilpet 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.

TheRealMDoerr · 2026-03-06T18:37:59Z

+  p = ::getenv("EXTSHM");
+  if (p != nullptr) {
+    vm_exit_during_initialization("EXTSHM is ON. Please remove EXTSHM from your environment.");
+  }


Was this added by mistake?

Looks wrong:

EXTSHM=OFF jdk/bin/java -version Error occurred during initialization of VM EXTSHM is ON. Please remove EXTSHM from your environment.

Mistake on my end, should be fixed now

TheRealMDoerr

LGTM. Thanks!

april-ivy · 2026-03-06T20:19:22Z

/integrate

openjdk · 2026-03-06T20:21:09Z

@aprilpet
Your change (at version af5d328) is now ready to be sponsored by a Committer.

tstuefe · 2026-03-07T05:41:51Z

I don't think the exit-when-EXTSHM-is-set should be removed without understanding first what the effects were for the 64kpages-with-SystemV-shm. I remember it being incompatible with some of the shmxxx() calls. The same ratio as given in the original comments we wrote 20 years ago.

I am fine with the removal of the flag, though.

TheRealMDoerr · 2026-03-07T14:09:28Z

I don't think the exit-when-EXTSHM-is-set should be removed without understanding first what the effects were for the 64kpages-with-SystemV-shm. I remember it being incompatible with some of the shmxxx() calls. The same ratio as given in the original comments we wrote 20 years ago.

vm_exit_during_initialization("EXTSHM is ON. Please remove EXTSHM from your environment."); is still in place in the version which I have approved.

I am fine with the removal of the flag, though.

Thanks for taking a look!

tstuefe · 2026-03-09T11:51:47Z

I don't think the exit-when-EXTSHM-is-set should be removed without understanding first what the effects were for the 64kpages-with-SystemV-shm. I remember it being incompatible with some of the shmxxx() calls. The same ratio as given in the original comments we wrote 20 years ago.

vm_exit_during_initialization("EXTSHM is ON. Please remove EXTSHM from your environment."); is still in place in the version which I have approved.

I am fine with the removal of the flag, though.

Thanks for taking a look!

Ah, I missed that part. Okay then.

tstuefe · 2026-03-09T11:52:09Z

/sponsor

openjdk · 2026-03-09T11:52:44Z

Going to push as commit e69fb77.
Since your change was applied there have been 34 commits pushed to the master branch:

2fc7bdc: 8379411: Use TestFramework scenarios in 837841
5e58808: 8378744: Obsolete NewSizeThreadIncrease flag
23adf6a: 8378569: Refactor test/jdk/java/net/httpclient/http3/H3ErrorHandlingTest.java to use JUnit
... and 31 more: https://git.openjdk.org/jdk/compare/f266079d26ffc1541e5d3146258f7d39188d1a84...master

Your commit was automatically rebased without conflicts.

openjdk · 2026-03-09T11:52:55Z

@tstuefe @april-ivy Pushed as commit e69fb77.

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

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Mar 6, 2026

openjdk bot added the rfr Pull request is ready for review label Mar 6, 2026

TheRealMDoerr suggested changes Mar 6, 2026

View reviewed changes

8378177: AllowExtshm flag cleanup on AIX

6dd9a50

april-ivy force-pushed the JDK-8378177 branch from ee8ca32 to 6dd9a50 Compare March 6, 2026 16:43

TheRealMDoerr reviewed Mar 6, 2026

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Remove duplicate EXTSHM check

af5d328

TheRealMDoerr approved these changes Mar 6, 2026

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openjdk bot added the ready Pull request is ready to be integrated label Mar 6, 2026

openjdk bot added the sponsor Pull request is ready to be sponsored label Mar 6, 2026

tstuefe approved these changes Mar 9, 2026

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openjdk bot closed this Mar 9, 2026

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Mar 9, 2026

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