RFR: JDK-8319314: NMT detail report slow or hangs for large number of mappings [v2]

[Thomas Stuefe]

> If a lot of mappings have been registered with NMT, NMT detail report may get so slow as to hang seemingly. 
> 
> 100 k mappings will take > 1 minute
> 1 million mappings never returns (I canceled the test after 90 minutes)
> 
> We burn all the time doing a sorted insert into the target array of the MemBaseline object. That sorted insert is pointless since the source array is already sorted by region base address.
> 
> Omitting the pointless sort drops the runtime for 1 million mappings from > 90 minutes to 48 seconds.
> 
> Tests: Tested locally. GHAs (Windows error unrelated).

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  Fix builds

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16480/files
  - new: https://git.openjdk.org/jdk/pull/16480/files/91f4da73..3d01f992

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16480&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16480&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16480.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16480/head:pull/16480

PR: https://git.openjdk.org/jdk/pull/16480