RFR: 8315923: pretouch_memory by atomic-add-0 fragments huge pages unexpectedly [v29]

[Johan Sjölen]

On Thu, 25 Jan 2024 08:25:20 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Liming Liu has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Use TestThreadGroup
>>  - Set it as default before parsing
>
> src/hotspot/os/linux/os_linux.cpp line 4402:
> 
>> 4400: 
>> 4401:   // Check the availability of MADV_POPULATE_WRITE.
>> 4402:   FLAG_SET_DEFAULT(UseMadvPopulateWrite, (::madvise(0, 0, MADV_POPULATE_WRITE) == 0));
> 
> Can we delay this to the first attempt? Switch it off if the first attempt returns EINVAL? Every system call saved at startup is good.

Is that possible? Won't that ~clobber~ replace the user-supplied parameter?

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PR Review Comment: https://git.openjdk.org/jdk/pull/15781#discussion_r1466193861