8347129: cpuset cgroups controller is required for no good reason

[jerboaa]

Please review this small change to make the cpuset cgroups controller optional as far as the JDK is concerned. The rationale is that:

• Some distributions now don't have it enabled by default (e.g. Fedora 41), which breaks automatic container detection logic.
• CPU limits enforced with --cpuset-cpus is reflected with the sched_getaffinity system call and, thus, the controller doesn't need to be mandatory. The current failure to detect the controller results in no container limits being detected with is bad.

The fix is rather simple. Make cpuset controller look-up from /proc/cgroups optional (like the pids controller) and continue. OSContainer::active_processor_count() still behaves as before (should there be a cpuset limit) as it's covered by os::Linux::active_processor_count() which serves as the upper bound of other container cpu limits.

While at it, I've also fixed the logging bug by re-arranging the const char* values. cpuset is index 0, cpu is index 1.

Testing:

• GHA
• Linux container tests in test/hotspot/jtreg/containers on Linux cgroups v1 and cgroups v2 as well as on an affected system (F41 on cg v2). All pass.

Thoughts?

---

Progress

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Warning

 ⚠️ Found leading lowercase letter in issue title for 8347129: cpuset cgroups controller is required for no good reason

Issue

• JDK-8347129: cpuset cgroups controller is required for no good reason (Bug - P3)

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