8347129: cpuset cgroups controller is required for no good reason #23037

jerboaa · 2025-01-10T14:14:59Z

Please review this small change to make the cpuset cgroups controller optional as far as the JDK is concerned. The rationale is that:

Some distributions now don't have it enabled by default (e.g. Fedora 41), which breaks automatic container detection logic.
CPU limits enforced with --cpuset-cpus is reflected with the sched_getaffinity system call and, thus, the controller doesn't need to be mandatory. The current failure to detect the controller results in no container limits being detected with is bad.

The fix is rather simple. Make cpuset controller look-up from /proc/cgroups optional (like the pids controller) and continue. OSContainer::active_processor_count() still behaves as before (should there be a cpuset limit) as it's covered by os::Linux::active_processor_count() which serves as the upper bound of other container cpu limits.

While at it, I've also fixed the logging bug by re-arranging the const char* values. cpuset is index 0, cpu is index 1.

Testing:

GHA
Linux container tests in test/hotspot/jtreg/containers on Linux cgroups v1 and cgroups v2 as well as on an affected system (F41 on cg v2). All pass.

Thoughts?

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⚠️ Found leading lowercase letter in issue title for 8347129: cpuset cgroups controller is required for no good reason

Issue

JDK-8347129: cpuset cgroups controller is required for no good reason (Bug - P3)

Reviewers

Thomas Stuefe (@tstuefe - Reviewer)
Ashutosh Mehra (@ashu-mehra - Committer)

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$ git fetch https://git.openjdk.org/jdk.git pull/23037/head:pull/23037
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Update a local copy of the PR:
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bridgekeeper · 2025-01-10T14:15:58Z

👋 Welcome back sgehwolf! 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 · 2025-01-10T14:16:04Z

@jerboaa 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:

8347129: cpuset cgroups controller is required for no good reason

Reviewed-by: stuefe, asmehra

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 65 new commits pushed to the master branch:

06ff4c1: 8347146: Convert IncludeLocalesPluginTest to use JUnit
db76f47: 8347720: [BACKOUT] Portable implementation of FORBID_C_FUNCTION and ALLOW_C_FUNCTION
e6902cf: 8323740: java.lang.ExceptionInInitializerError when trying to load XML classes in wrong order
a01e92c: 8347724: Replace SIZE_FORMAT in jfr directory
d002933: 8347286: (fs) Remove some extensions from java/nio/file/Files/probeContentType/Basic.java
d532019: 8347143: [aix] Fix strdup use in os::dll_load
dfd215b: 8347376: tools/jlink/runtimeImage/JavaSEReproducibleTest.java and PackagedModulesVsRuntimeImageLinkTest.java failed after JDK-8321413
a49f833: 8346045: Cleanup of security library tests calling Security Manager APIs
56c7800: 8347381: Upgrade jQuery UI to version 1.14.1
1c64a45: 8347501: Make static-launcher fails after JDK-8346669
... and 55 more: https://git.openjdk.org/jdk/compare/1f457977f062e4ed219c6fa0fe26cb42acaf4bf2...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.

openjdk · 2025-01-10T14:16:41Z

@jerboaa 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 · 2025-01-10T14:19:43Z

Webrevs

00: Full (6ac4d329)

zapster · 2025-01-14T08:45:31Z

Not a reviewer, but I've tested your change in the context of https://github.com/oracle/graal native image and it fixes the problems that we were seeing. Thanks!

jerboaa · 2025-01-14T09:42:45Z

@dholmes-ora @tstuefe Could you please help review this simple change? Thanks in advance!

tstuefe

Sorry, just saw that now. Okay.

jerboaa · 2025-01-14T15:09:26Z

Thanks for the review!

ashu-mehra · 2025-01-14T15:18:44Z

@jerboaa Should this block be updated to not return false as the cpuset is now an optional subsystem.

jdk/src/hotspot/os/linux/cgroupSubsystem_linux.cpp

Lines 498 to 503 in 56c7800

    
           if (!cg_infos[CPUSET_IDX]._data_complete) { 
        
             log_debug(os, container)("Required cgroup v1 cpuset subsystem not found"); 
        
             cleanup(cg_infos); 
        
             *flags = INVALID_CGROUPS_V1; 
        
             return false; 
        
           }

jerboaa · 2025-01-14T16:58:08Z

@jerboaa Should this block be updated to not return false as the cpuset is now an optional subsystem.

jdk/src/hotspot/os/linux/cgroupSubsystem_linux.cpp

Lines 498 to 503 in 56c7800

if (!cg_infos[CPUSET_IDX]._data_complete) {

log_debug(os, container)("Required cgroup v1 cpuset subsystem not found");

cleanup(cg_infos);

*flags = INVALID_CGROUPS_V1;

return false;

}

@ashu-mehra Thanks for looking at it!

I'm in two minds about this. Why? a) cgroups v1 is becoming increasingly legacy b) the chance that an old v1 system would no longer enable cpusets controller seems unlikely. So while it seems consistent to remove this for cg v1 too, it's unlikely that such a system exists. For example Fedora 41 where this has been observed no longer supports cg v1. I'd expect for other distros to follow. New distros will likely only support cg v2.

For those reasons I'd be inclined to keep the patch as-is as it would be less risky for the cg v1 version.

Thoughts?

ashu-mehra · 2025-01-14T17:52:22Z

@jerboaa Thanks for the explanation. I agree with you. I think its fine to keep cg v1 as is.

ashu-mehra

looks good.

jerboaa · 2025-01-14T19:39:17Z

/integrate

openjdk · 2025-01-14T19:40:53Z

Going to push as commit 2de71d0.
Since your change was applied there have been 66 commits pushed to the master branch:

4c30933: 8346971: [ubsan] psCardTable.cpp:131:24: runtime error: large index is out of bounds
06ff4c1: 8347146: Convert IncludeLocalesPluginTest to use JUnit
db76f47: 8347720: [BACKOUT] Portable implementation of FORBID_C_FUNCTION and ALLOW_C_FUNCTION
e6902cf: 8323740: java.lang.ExceptionInInitializerError when trying to load XML classes in wrong order
a01e92c: 8347724: Replace SIZE_FORMAT in jfr directory
d002933: 8347286: (fs) Remove some extensions from java/nio/file/Files/probeContentType/Basic.java
d532019: 8347143: [aix] Fix strdup use in os::dll_load
dfd215b: 8347376: tools/jlink/runtimeImage/JavaSEReproducibleTest.java and PackagedModulesVsRuntimeImageLinkTest.java failed after JDK-8321413
a49f833: 8346045: Cleanup of security library tests calling Security Manager APIs
56c7800: 8347381: Upgrade jQuery UI to version 1.14.1
... and 56 more: https://git.openjdk.org/jdk/compare/1f457977f062e4ed219c6fa0fe26cb42acaf4bf2...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-01-14T19:41:06Z

@jerboaa Pushed as commit 2de71d0.

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

jerboaa added 3 commits January 10, 2025 11:57

Fix container logging bug (mentions 'cpu' while it should be 'cpuset')

804bc9a

8347129: cpuset cgroups controller is required for no good reason

64a0037

Fix comment

6ac4d32

openjdk bot added the rfr Pull request is ready for review label Jan 10, 2025

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Jan 10, 2025

tstuefe approved these changes Jan 14, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Jan 14, 2025

ashu-mehra approved these changes Jan 14, 2025

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graalvmbot mentioned this pull request Jan 20, 2025

[GR-61425] Update labsjdk to 25+6-jvmci-b01 oracle/graal#10513

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8347129: cpuset cgroups controller is required for no good reason #23037

8347129: cpuset cgroups controller is required for no good reason #23037

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