8356868: Not all cgroup parameters are made available #25388

caspernorrbin · 2025-05-22T09:06:15Z

Hi everyone,

This PR improves cgroup support by exposing additional parameters that are currently not available. These parameters would enable more advanced features that rely on CPU and memory usage data.

The new parameters are:

CPU usage: cpuacct.usage (cgroup v1) and cpu.stat (cgroup v2), which allow precise tracking of consumed CPU time.
Peak memory usage: memory.peak (cgroup v2). While the cgroup v1 equivalent (memory.max_usage_in_bytes) was already available, cgroup v2 previously returned OSCONTAINER_ERROR — this has now been fixed.
Memory throttle limit: memory.high (cgroup v2). There is no direct equivalent in cgroup v1, but since most systems use cgroup v2, exposing this parameter enables finer-grained memory control for those systems.

Testing:

All container tests under /test/hotspot/jtreg/containers/
Manually inspected the new parameters in both cgroup v1 and v2 container environments with the relevant settings applied.

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8356868: Not all cgroup parameters are made available (Enhancement - P4)

Reviewers

Severin Gehwolf (@jerboaa - Reviewer)
Gerard Ziemski (@gerard-ziemski - Reviewer)

Reviewing

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$ git fetch https://git.openjdk.org/jdk.git pull/25388/head:pull/25388
$ git checkout pull/25388

Update a local copy of the PR:
$ git checkout pull/25388
$ git pull https://git.openjdk.org/jdk.git pull/25388/head

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$ git pr checkout 25388

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https://git.openjdk.org/jdk/pull/25388.diff

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bridgekeeper · 2025-05-22T09:06:52Z

👋 Welcome back cnorrbin! 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 · 2025-05-22T09:07:04Z

@caspernorrbin 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:

8356868: Not all cgroup parameters are made available

Reviewed-by: sgehwolf, gziemski

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 511 new commits pushed to the master branch:

c6ab63d: 8359735: [Ubuntu 25.10] java/lang/ProcessBuilder/Basic.java, java/lang/ProcessHandle/InfoTest.java fail due to rust-coreutils
ff54a64: 8360049: CodeInvalidationReasonTest.java fails with ZGC on AArch64
c11f36e: 8356708: C2: loop strip mining expansion doesn't take sunk stores into account
... and 508 more: https://git.openjdk.org/jdk/compare/277bb208a2c6de888c57285854b6f5d030021f94...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 · 2025-05-22T09:07:45Z

@caspernorrbin 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 · 2025-05-22T09:11:05Z

Webrevs

01: Full - Incremental (878327c5)
00: Full (cd113cba)

jerboaa

This looks fine to me. One suggestion as I think the cpu usage might be 0 and greater.

src/hotspot/os/linux/os_linux.cpp

Co-authored-by: Severin Gehwolf <[email protected]>

caspernorrbin · 2025-06-04T11:29:26Z

This looks fine to me. One suggestion as I think the cpu usage might be 0 and greater.

Thank you for reviewing! Have changed the check to use >= instead.

gerard-ziemski

LGTM, though I did have one feedback.

gerard-ziemski · 2025-06-20T16:47:56Z

src/hotspot/os/linux/cgroupV1Subsystem_linux.cpp

+jlong CgroupV1CpuacctController::cpu_usage_in_micros() {
+  julong cpu_usage;
+  CONTAINER_READ_NUMBER_CHECKED(reader(), "/cpuacct.usage", "CPU Usage", cpu_usage);
+  // Output is in nanoseconds, convert to microseconds.
+  return (jlong)cpu_usage / 1000;
+}
+


Why don't we report the original value in nanos, if it is available?

This is new API, so no-one is using this yet, right?

I centered it around cgroup v2, which only reports the usage in micros. Cgroup v1 is deprecated for most systems so shouldn't really be used. It made more sense to use micros instead of padding the value most will see with a bunch of zeros.

caspernorrbin · 2025-06-25T08:31:49Z

Thank you for the reviews. With no objections, I'll go ahead and integrate.

/integrate

openjdk · 2025-06-25T08:32:54Z

Going to push as commit 850bc20.
Since your change was applied there have been 558 commits pushed to the master branch:

75ce44a: 8355319: Update Manpage for Compact Object Headers (Production)
5c4f92b: 8359788: Internal Error: assert(get_instanceKlass()->is_loaded()) failed: must be at least loaded
263e32b: 8358694: VM asserts if CodeCacheSegmentSize is not a power of 2
... and 555 more: https://git.openjdk.org/jdk/compare/277bb208a2c6de888c57285854b6f5d030021f94...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-06-25T08:33:01Z

@caspernorrbin Pushed as commit 850bc20.

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

added cgroup parameters

cd113cb

openjdk bot changed the title ~~8356868~~ 8356868: Not all cgroup parameters are made available May 22, 2025

openjdk bot added the rfr Pull request is ready for review label May 22, 2025

openjdk bot added the hotspot-runtime [email protected] label May 22, 2025

jerboaa approved these changes Jun 3, 2025

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src/hotspot/os/linux/os_linux.cpp Outdated Show resolved Hide resolved

openjdk bot added the ready Pull request is ready to be integrated label Jun 3, 2025

update cpu usage to use >=

878327c

Co-authored-by: Severin Gehwolf <[email protected]>

openjdk bot removed the ready Pull request is ready to be integrated label Jun 4, 2025

jerboaa approved these changes Jun 4, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Jun 4, 2025

gerard-ziemski approved these changes Jun 20, 2025

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openjdk bot closed this Jun 25, 2025

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jun 25, 2025

graalvmbot mentioned this pull request Jul 2, 2025

[GR-66564] Adopt JDK-8356868: Not all cgroup parameters are made available oracle/graal#11526

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