[jdk11u-dev] RFR: 8234930: Use MAP_JIT when allocating pages for code cache on macOS [v2]

[Goetz Lindenmaier]

On Tue, 2 Nov 2021 20:05:45 GMT, Vladimir Kempik <vkempik at openjdk.org> wrote:

>> Please review this backport of JDK-8234930 to jdk11u-dev.
>> This is a prerequest for mac-aarch64
>> It's not applying clean due to the miss of these two patches
>> JDK-8253639: Change os::attempt_reserve_memory_at parameter order
>> JDK-8253650: Cleanup: remove alignment_hint parameter from os::reserve_memory
>> But they aren't critical and the patch can easily be modified
>
> Vladimir Kempik has updated the pull request incrementally with one additional commit since the last revision:
>
>   Fix up windows

Hi,
I think a mac port for aarch64 is an essential contribution to 11. Thank you for taking the effort of backporting it!
But I second Thomas' view that the above patches are an uncommon amount of shared changes for a new feature in a release in maintenance mode.
I know there have already been quite a number of bigger changes to the aarch64, mac and windows files. They mainly touched one platform limiting the risk. This one is a change affecting all platforms in a very essential component, the memory management.
Previous feature backports were implemented very carefully to not change existing code, for example the Shenandoah port that can entirely be removed by configure flags: https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2020-July/003472.html .
I would appreciate if you could explore a similar approach for this change.

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PR: https://git.openjdk.java.net/jdk11u-dev/pull/580