RFR: 8207812: Implement Dynamic CDS Archive

[Claes Redestad]

On 2019-04-22 19:06, Calvin Cheung wrote:
> 
> The first 2 apps only have 2 to 3 classes in the dynamic archive. So the 
> overhead is likely due to having to open and map the dynamic archive and 
> performs checking on header, etc. For small apps, I think it's better to 
> use a single archive. The Netty app has around 1400  classes in the 
> dynamic archive; the Spring app has about 3700 classes in the dynamic 
> archive.

Could this be the overhead due -XX:+VerifySharedSpaces being enabled
when enabling dynamic archives - possibly leading to us to verify even
the base CDS archive (which we wouldn't do, normally).

I've recently proposed this verification be disabled by default in all
configurations[1], which would eliminate this causing surprise
regressions when layering archives.

Thanks!

/Claes

[1] https://bugs.openjdk.java.net/browse/JDK-8221478