Hi, Could I please get a review of this fix to the detection heuristic of cgroup v1 vs cgroup v2? Matthias (in CC) discovered that on some old systems the JDK Metrics code throws InternalError caused by wrong detection logic when Metrics are being created on Linux.
The reason for this is that hierarchy IDs of 0 in /proc/cgroups is being used as a heuristic to detect cgroups v2 systems. Apparently some old systems like RHEL 6 and SLES 11 have no cgroups controllers mounted, thus, triggering a false positive. The fix is to also look at /proc/self/mountinfo and correct logic in this case. Bug: https://bugs.openjdk.java.net/browse/JDK-8239559 webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8239559/01/webrev/ Testing: docker/cgroups tests on hybrid (cgroups v1) and unified hierarchy (cgroups v2). New regression test. Looks good here. Unfortunately, I wasn't able to reproduce this on an actual affected system. I somewhat reproduced via the derived regression test based on data from reporters. I'd appreciate any testing on systems where this reproduces. Thanks, Severin
