[jdk21u-dev] RFR: 8315923: pretouch_memory by atomic-add-0 fragments huge pages unexpectedly

[Liming Liu]

On Mon, 8 Jul 2024 11:09:37 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This pull request ports JDK-8315923 back to JDK-21, as JDK-21 still uses atomic-add-0 to pretouch memory and results fragmented huge pages. This backport has the following differences from its original version:
>> 
>> - TestTransparentHugePageUsage.java gets deleted as it was deleted in JDK-8324776;
>> - nullptr is adopted in pretouch_thp_and_use_concurrent, as it is a part of  JDK-8327171;
>> - JDK-8324781 is included, as JDK-8324781 only makes changes to testcases.
>
> I have questions:
> 
> 1. If [JDK-8324781](https://bugs.openjdk.org/browse/JDK-8324781) is included, you need to say `/issue add JDK-8324781`, and later request approval for it as well.
> 2. Looking at issue links, what about [JDK-8325218](https://bugs.openjdk.org/browse/JDK-8325218)?

Hi @shipilev! Thank you for your suggestions. The root case of JDK-8324781 and JDK-8325218 are the same, so they were solved in the same commit. I added them altogether.

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PR Comment: https://git.openjdk.org/jdk21u-dev/pull/825#issuecomment-2216617528