cgroups.go picking up memory.pressure mountpoint

[robdinh]

Describe the problem Since this commit was applied, systemd creates a cgroup2 mount for memory.pressure.

$ pid=$(sudo systemctl show --property MainPID cockroachdb | cut -d'=' -f2)
$ sudo cat /proc/$pid/mountinfo | grep cgroup2 | cut -d' ' -f5
/sys/fs/cgroup
/sys/fs/cgroup/production.slice/production-storage.slice/cockroachdb.service/memory.pressure

With ProtectControlGroups=yes option set, /pkg/util/cgroups/cgroups.go/ ends up detecting the memory.pressure path. This is causes a noisy log showing this message:

"message": "unable to get CPU capacity: error when read cpu quota from cgroup v2 at ‹/sys/fs/cgroup/production.slice/production-storage.slice/cockroachdb.service/memory.pressure/production.slice/production-storage.slice/cockroachdb.service/cpu.max›: open ‹/sys/fs/cgroup/production.slice/production-storage.slice/cockroachdb.service/memory.pressure/production.slice/production-storage.slice/cockroachdb.service/cpu.max›: not a directory"

where maxFilePath in detectCPUQuotaInV2() is a join of strings of:

• getCgroupDetails() returns "/sys/fs/cgroup/production.slice/production-storage.slice/cockroachdb.service/memory.pressure"
• detectCntrlPath() returns "/production.slice/production-storage.slice/cockroachdb.service"
• cgroupV2CPUMaxFilename = "cpu.max"

To Reproduce This continue might be how /pkg/util/cgroups/cgroups.go/ picks other cgroup2 mounts, where it used to be a return.

Expected behavior maxFilePath should be /sys/fs/cgroup/production.slice/production-storage.slice/cockroachdb.service/cpu.max

Environment:

• CockroachDB v22.2.13
• Server OS: Debian GNU/Linux 12 (bookworm)

Jira issue: CRDB-32361

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