RFR: 8317692: jcmd GC.heap_dump performance regression after JDK-8292818 [v3]

[Hannes Greule]

> See the bug description for more information.
> 
> This implementation brings down the time to take a heap dump on the example application in the bug report to <2 seconds on my machine.

Hannes Greule has updated the pull request incrementally with one additional commit since the last revision:

  add more tests

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16083/files
  - new: https://git.openjdk.org/jdk/pull/16083/files/63887422..26f5dcdd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16083&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16083&range=01-02

  Stats: 65 lines in 1 file changed: 41 ins; 4 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/16083.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16083/head:pull/16083

PR: https://git.openjdk.org/jdk/pull/16083