RFR: 8303215: Make thread stacks not use huge pages [v3]

[Poonam Bajaj]

On Mon, 29 May 2023 01:19:57 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Poonam Bajaj has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   addressed review comments
>
> src/hotspot/os/linux/os_linux.cpp line 934:
> 
>> 932:   if (stack_size >= os::Linux::default_large_page_size() && is_aligned(stack_size, os::Linux::default_large_page_size())) {
>> 933:     stack_size += os::vm_page_size();
>> 934:   }
> 
> Do we need to watch for a zero default size here so that we don't expand all stacks by a page?

Added a check for zero default page size. Please review.

> src/hotspot/os/linux/os_linux.cpp line 3754:
> 
>> 3752: 
>> 3753: void os::large_page_init() {
>> 3754:   // Scan default large page size
> 
> Suggestion:
> 
> // Always initialize the default large page size even if large pages are not being used.

Changed the comment.

> src/hotspot/os_cpu/linux_aarch64/globals_linux_aarch64.hpp line 34:
> 
>> 32: define_pd_global(bool, DontYieldALot,            false);
>> 33: 
>> 34: // set default stack sizes < 2MB so as to prevent stacks from getting
> 
> /set/Set/

Done.

> src/hotspot/os_cpu/linux_aarch64/globals_linux_aarch64.hpp line 36:
> 
>> 34: // set default stack sizes < 2MB so as to prevent stacks from getting
>> 35: // large-page aligned and backed by THPs on systems where 2MB is the
>> 36: // default huge page size. For non-JavaThreads, glibc adds an additional
> 
> s/adds/may add/

Done.

> src/hotspot/os_cpu/linux_aarch64/globals_linux_aarch64.hpp line 38:
> 
>> 36: // default huge page size. For non-JavaThreads, glibc adds an additional
>> 37: // guard page to the total stack size, so to keep the default sizes same
>> 38: // for all the following flags, we set them to 2 pages less than 2MB.
> 
> I still think we need to at least mention we assume 4K page here.

@dholmes-ora I have updated the comment, please review.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/14105#discussion_r1210794132
PR Review Comment: https://git.openjdk.org/jdk/pull/14105#discussion_r1210794392
PR Review Comment: https://git.openjdk.org/jdk/pull/14105#discussion_r1210794644
PR Review Comment: https://git.openjdk.org/jdk/pull/14105#discussion_r1210794720
PR Review Comment: https://git.openjdk.org/jdk/pull/14105#discussion_r1210793561