RFR: JDK-8312182: THPs cause huge RSS due to thread start timing issue [v2]

[David Holmes]

On Wed, 19 Jul 2023 15:56:42 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> src/hotspot/os/linux/os_linux.cpp line 932:
>> 
>>> 930:   // into one VMA.
>>> 931:   if (PreventTHPsForThreadStacks) {
>>> 932:     guard_size = MAX2(guard_size, os::vm_page_size());
>> 
>> It would be helpful to add a comment clarifying that we don't add glibc guard pages for JavaThreads and Compiler threads (i.e. default_guard_size returns 0 for these threads), and when PreventTHPsforThreadStacks is true, JavaThreads and Compiler threads will have both the glibc guard page and JVM guard pages.
>
> Hmm. We already have a comment in place in `os::Linux::default_guard_size(thr_type);`. Maybe @dholmes-ora is right; I will add this logic to default_guard_size and extent the comment over there.

Thanks for moving the logic.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14919#discussion_r1269010115