RFR: 8252842: Extend jmap to support parallel heap dump [v21]

[Chris Plummer]

On Mon, 26 Apr 2021 12:45:56 GMT, Lin Zang <lzang at openjdk.org> wrote:

>> 8252842: Extend jmap to support parallel heap dump
>
> Lin Zang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 27 commits:
> 
>  - Merge branch 'master' into par-dump
>  - refine with several fix
>  - Merge branch 'master' into par-dump
>  - Merge branch 'master' into par-dump
>  - Typo fix
>  - remove parallel option and dumpheapext command
>  - Revert "hide the dumpheapext error message"
>    
>    This reverts commit 1af0e1e2bfab4f5d079c03ff0cb25067acacdac4.
>  - resize large object threshold
>  - Merge branch 'master' into par-dump
>  - Merge branch 'master' into par-dump
>  - ... and 17 more: https://git.openjdk.java.net/jdk/compare/c3ac6900...6d14790a

src/hotspot/share/services/heapDumperCompression.cpp line 240:

> 238: }
> 239: 
> 240: void CompressionBackend::flush_buffer_without_lock(MonitorLocker* ml) {

I'm trying to think of a better name since "without_lock" makes it sound like there is no locking, but there is. The difference is the lock is passed in. How about just calling it `flush_buffer(MonitorLocker* ml)` and rely on C++ method overloading to disambiguate it from `flush_buffer()`.

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PR: https://git.openjdk.java.net/jdk/pull/2261