• Bug#1108294: kernel 6.12 breaks cgroup awareness of openjdk 21

    From Ben Hutchings@21:1/5 to Ben Hutchings on Wed Jul 9 00:50:02 2025
    XPost: linux.debian.kernel

    Control: tag -1 patch

    On Thu, 2025-06-26 at 19:17 +0200, Ben Hutchings wrote:
    On Thu, 2025-06-26 at 18:24 +0200, Ben Hutchings wrote:
    [...]
    Thank you for bringing this to our attention.

    I don't think it makes sense for us to re-enable cgroups v1, given that
    it has been deprecated for so long and OpenJDK itself can use v2.

    I will look into whether we can instead provide only a /proc/cgroups
    file, which seems to be all that OpenJDK actually needed.

    In fact this may be as simple as reverting:

    commit af000ce85293b8e608f696f0c6c280bc3a75887f
    Author: Michal Koutný <[email protected]>
    Date: Mon Sep 9 18:32:23 2024 +0200

    cgroup: Do not report unavailable v1 controllers in /proc/cgroups

    but I have not yet tested that.

    Yes, this seems to work.

    I compiled the following class:

    --- BEGIN ---
    import java.lang.System;

    class Main {
    public static void main(String[] args) {
    int count = Integer.parseInt(args[0]);
    char[] one_mb;
    int i;

    for (i = 0; i != count; i++) {
    one_mb = new char[0x100000];
    System.out.println(one_mb[0] | one_mb[0xfffff]);
    }
    }
    };
    --- END ---

    and ran it with an argument of "1000".

    I used a podman container of Debian limited to 50 MiB. With the current
    kernel from trixie, it OOMs. With that commit reverted, it runs to
    completion.

    I will open an MR tomorrow.

    Ben.

    --
    Ben Hutchings
    73.46% of all statistics are made up.

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  • From Ben Hutchings@21:1/5 to Ben Hutchings on Wed Jul 9 14:00:02 2025
    XPost: linux.debian.kernel

    On Wed, 2025-07-09 at 00:46 +0200, Ben Hutchings wrote:
    [...]
    I will open an MR tomorrow.

    Opened <https://salsa.debian.org/kernel-team/linux/-/merge_requests/1572>.

    Ben.

    --
    Ben Hutchings
    73.46% of all statistics are made up.

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    =k/GB
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