RFR: 8298992: runtime/NMT/SummarySanityCheck.java failed with "Total commi…tted (MMMMMM) did not match the summarized committed (NNNNNN) [v2]

[Afshin Zafari]

> During exhaustive tests, it is observed that during taking snapshot of NMT metrics it is possible that new allocations happen concurrently, although a `ThreadCritical` is used during copying current metrics to the snapshot.
> A loop is surrounding the copying and checks whether the copied and original are the same.

Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:

  move the copy_to function from header to cpp file.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15306/files
  - new: https://git.openjdk.org/jdk/pull/15306/files/09cf7076..a55e417a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15306&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15306&range=00-01

  Stats: 42 lines in 2 files changed: 24 ins; 17 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15306.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15306/head:pull/15306

PR: https://git.openjdk.org/jdk/pull/15306