[jdk21u] RFR: 8319650: Improve heap dump performance with class metadata caching

[Aleksey Shipilev]

On Tue, 21 Nov 2023 12:28:53 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Unclean backport to improve heap dump performance. The uncleanliness comes from [JDK-8306441](https://bugs.openjdk.org/browse/JDK-8306441) that does not exist in JDK 21, and which I don't think we want to backport at the moment. I had to add a few more `ResourceMark`-s near `HeapDumpWriter` to manage the cache allocations.
> 
> Additional testing:
>  - [x] MacOS AArch64 server release, heap dump performance improved
>  - [x]  Linux x86_64 server fastdebug, serviceability/ (contains heap dump tests)
>  - [x] Linux x86_64 server fastdebug, runtime/ErrorHandling (contains heap dump on failure tests)
>  - [x] Linux x86_64 server fastdebug, gc/epsilon (contains heap dump on failure tests)
>  - [x] Linux x86_64 server fastdebug, sun/tools/jhsdb (contains heap dump tests)

Closing in favor of https://github.com/openjdk/jdk21u-dev/pull/8

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PR Comment: https://git.openjdk.org/jdk21u/pull/388#issuecomment-1853680031