[jdk8u-dev] RFR: 8231111: Cgroups v2: Rework Metrics in java.base so as to recognize unified hierarchy

[Jonathan Dowland]

This is a backport of [4def210a22faaec6b47912dd314e6365ea48d28f](https://github.com/openjdk/jdk/commit/4def210a22faaec6b47912dd314e6365ea48d28f) for jdk8u-dev as part of an effort to backport cgroups v2 support.

It does not apply clean. Paths need unshuffling. A number of changes were needed for 8u support. I've structured the PR as separate commits, with each change made in a separate commit for (hopefully) ease of review.

Not all the new tests pass:     TestDockerMemoryMetrics  failing one, specifically:

    Exception in thread "main" java.lang.RuntimeException: Memory and swap limit not equal, expected : [209715200, 1073741824], got : [209715200, 864026624]

I think this is fixed in a further patch to backport, and will confirm.

-------------

Commit messages:
 - TestCgroupSubsystemController: rework use of Files.writeString
 - CgroupSubsystemController: fix library paths
 - TestCgroupSubsystemController: fix jtreg @library path
 - Replace Arrays.compare with Arrays.equals
 - incorporate (part of) 8275713: TestDockerMemoryMetrics test fails on recent runc
 - update mapfile for new JNI method name
 - tests for the backport
 - CgroupSubsystemFactory: remove logging lines
 - Metrics => CgroupV1Subsystem.java
 - Metrics.java: easy commit, mostly doc-only hunks
 - ... and 5 more: https://git.openjdk.org/jdk8u-dev/compare/ba408e55...1c5cdd6e

Changes: https://git.openjdk.org/jdk8u-dev/pull/121/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=121&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8231111
  Stats: 5335 lines in 33 files changed: 3621 ins; 1582 del; 132 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/121.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/121/head:pull/121

PR: https://git.openjdk.org/jdk8u-dev/pull/121