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

[Yumin Qi]

On Tue, 23 Feb 2021 09:30:11 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Should we only use this on platforms where one can have different base page sizes *on the same platform*? Since the only one of our platforms I know where this could even be an issue are aarch, and possibly AIX.
>
> It doesn't make sense always to use 64k alignment, as most builds are for a single platform. By all means, it can be a useful option, but in general we want to minimize file sizes.

> Should we only use this on platforms where one can have different base page sizes _on the same platform_? Since the only one of our platforms I know where this could even be an issue are aarch, and possibly AIX.

@tstuefe @theRealAph @iklam 
Thanks for review! Currently linux-aarch64, macos-aarch64(I don't know AIX) can be configured with 4K/64K page size. To make one build compatible with both, this change takes the 64K (or bigger) as the default region alignment. It is hard to make it optional I think. Will check the possibility of more options.

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