RFR: 8341913: Support CDS heap dumping for Shenandoah and Epsilon

[Ioi Lam]

On Thu, 10 Oct 2024 16:33:46 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This follows [JDK-8298614](https://bugs.openjdk.org/browse/JDK-8298614) and completes support for CDS dumping for Shenandoah and Epsilon. We have already enabled these in Leyden repo. I took a chance to clean up the code a bit. Shenandoah support is tested by the existing test. Epsilon support was tested manually, since it is quite likely flaky (= depends on pre-dump conditions not to run into OOM) to include in tests.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug server, `runtime/cds`
>  - [x] Linux x86_64 fastdebug server, `runtime/cds`, `-XX:+UseShenandoahGC`
>  - [x] Linux x86_64 fastdebug server, manual dumps with `-XX:+UseEpsilonGC`

test/hotspot/jtreg/runtime/cds/appcds/sharedStrings/IncompatibleOptions.java line 114:

> 112:         testDump(2, "-XX:+UseParallelGC", "", "", false);
> 113:         testDump(3, "-XX:+UseSerialGC", "", "", false);
> 114:         testDump(4, "-XX:+UseShenandoahGC", "", "", false);

Should this be inside ` if (GC.Shenandoah.isSupported())` ?

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

PR Review Comment: https://git.openjdk.org/jdk/pull/21457#discussion_r1809700385