RFR: JDK-8312018: Improve zero-base-optimized reservation of class space [v4]

Wed Jul 19 12:41:43 UTC 2023

On Tue, 18 Jul 2023 19:32:30 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> I think we should document the interaction with "-Xshare:dump". Maybe we should add comments that the value of `CompressedKlass::base()` is irrelevant to the dumped CDS archive when running "java -Xshared:dump", because of this code.
> 

Okay. Maybe in a different RFE? Since its a bit tangential to what this patch does.

> I.e., if CDS is enabled, we always use a non-zero based encoding.

Not necessarily. If CDS is enabled and we don't get the preferred mapping address, we will fallback to traditional Klass range reservation and potentially go zero based. With this patch, that path is optimized too.

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PR Comment: https://git.openjdk.org/jdk/pull/14867#issuecomment-1642009430