RFR: 8292329: Enable CDS shared heap for zero builds

[Thomas Stuefe]

On Tue, 23 Aug 2022 15:56:35 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> ZERO uses UseSerialGC by default. When we dump the default CDS archive during the build process, it fails to dump the shared heap (which requires G1GC).
> 
> The fix is to force -XX:+UseG1GC when dumping the default CDS archive during the build process.
> 
> Speed up:
> 
> (Before)
> $ perf stat -r 40 ./images/jdk/bin/java -version
> 0.018080 +- 0.000388 seconds time elapsed ( +- 2.15% )
> 
> (After)
> $ perf stat -r 40 ./images/jdk/bin/java -version
> 0.011986 +- 0.000205 seconds time elapsed ( +- 1.71% )

Stupid question, does that not mean that the CDS dump generated at build time is not usable with the VM at runtime if that is started with default options?

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PR: https://git.openjdk.org/jdk/pull/9984