RFR: 8236847: CDS archive with 4K alignment unusable on machines with 64k pages [v7]

[Thomas Stuefe]

On Wed, 10 Mar 2021 18:44:18 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Yumin Qi has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:
>> 
>>  - Merge branch 'master' into jdk-8236847
>>  - Merge master
>>  - Add --enable-compatible-cds-alignment for linux-aarch64 and macosx-x64 in jib job
>>  - Switch to enble compatible-cds-alignment at configuration
>>  - Make CDS core region alignment configurable at build time
>>  - Make 64K core region alignment only for specific platforms, also fixed comments as suggestions.
>>  - 8236847: CDS archive with 4K alignment unusable on machines with 64k pages
>
> I think this is fine. "compatible" vs "default" is a good compromise. Small remarks inside. Sorry for all the bikeshedding!
> 
> Cheers, Thomas

> The page size on aarch64 seems to be configurable to 4, 64 and 1MB (and
> also 16KB on some platforms, apparently M1 is the case). Do we know if
> anyone that plans to use 1MB page sizes?

I am not sure if it is possible to use a *base page size* of 1M, and even if it were, it would be terribly inefficient. And nothing prevents you, at least on Linux, from running with -XX:+UseLargePages, which would be a more sensible way to use large pages.

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

PR: https://git.openjdk.java.net/jdk/pull/2651