RFR: 8322043: HeapDumper should use parallel dump by default [v5]

[David Holmes]

On Wed, 17 Apr 2024 20:42:54 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

>> The fix makes VM heap dumping parallel by default.
>> `jcmd GC.heap_dump` and `jmap -dump` had parallel dumping by default, the fix affects `HotSpotDiagnosticMXBean.dumpHeap()`, `-XX:+HeapDumpBeforeFullGC`, `-XX:+HeapDumpAfterFullGC` and `-XX:+HeapDumpOnOutOfMemoryError`.
>> 
>> Testing:
>>   - manually tested different heap dump scenarios with `-Xlog:heapdump`;
>>   - tier1,tier2,hs-tier5-svc;
>>   - all reg.tests that use heap dump.
>
> Alex Menkov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   removed unneeded cast

One nit, otherwise looks good. Thanks

src/hotspot/share/services/diagnosticCommand.cpp line 523:

> 521:   // and makes it easier to browse.
> 522:   HeapDumper dumper(!_all.value() /* request GC if _all is false*/);
> 523:   dumper.dump(_filename.value(), output(), (int)level, _overwrite.value(), (uint)parallel);

I'm not sure what the prevalent style is for cast operators, but I don't see any point doing this in this PR when the file is otherwise untouched. Thanks.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18748#pullrequestreview-2030177251
PR Review Comment: https://git.openjdk.org/jdk/pull/18748#discussion_r1584110521