RFR: 8343191: Cgroup v1 subsystem fails to set subsystem path [v3]

[Sergey Chernyshev]

On Tue, 12 Nov 2024 19:41:50 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Sergey Chernyshev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
>> 
>>  - Merge branch 'master' into JDK-8343191
>>  - patch reimplemented
>>  - fix the logic that skips duplicate controller's mount points
>>  - 8343191: Cgroup v1 subsystem fails to set subsystem path
>
> src/java.base/linux/classes/jdk/internal/platform/cgroupv1/CgroupV1SubsystemController.java line 46:
> 
>> 44:     }
>> 45: 
>> 46:     public void setPath(String cgroupPath) {
> 
> This should behave the same as Hotspot and also append the cgroup path to the mount point. Then let [JDK-8336881](https://bugs.openjdk.org/browse/JDK-8336881) kick in to reduce it down to the mount point (if necessary).

Correct. I double checked the behavior in cg v2:


sudo cgcreate -g memory:/test
sudo cgcreate -g memory:/test/test
sudo cgset -r memory.max=50m test
sudo cgset -r memory.swap.max=0 test
sudo cgset -r memory.max=100m test/test
sudo cgset -r memory.swap.max=0 test/test

with the above setup, allocations smaller than the outer group size will work, bigger will be oom-killed.


$ sudo cgexec -g memory:/test/test sh -c "head -c 45m /dev/zero | tail | wc -c"

47185920

$ sudo cgexec -g memory:/test/test sh -c "head -c 55m /dev/zero | tail | wc -c"

0
Killed


I'll update the PR next week.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21808#discussion_r1838979707