[jdk8u-dev] RFR: 8303215: Make thread stacks not use huge pages

[Takuya Kiriyama]

On Fri, 16 Jan 2026 12:11:22 GMT, Takuya Kiriyama <tkiriyama at openjdk.org> wrote:

> Hi All,
> 
> I would like to backport the fix for bug JDK-8303215 to JDK 8. This bug addresses an issue with Transparent Huge Pages (THP) and thread stack allocation.
> This fix is unclean, but almost clean backport from jdk11.
> 
> 1. Backport:
> The fix is almost clean from jdk11, but there is a slight difference.
> 
> - os_linux.cpp
> Since JDK 8 does not include JDK-8183552, we need to add one more include statement. JDK-8183552 will likely not be backported to 8u.
> 
> - globals_linux_aarch64.hpp
> In JDK 11, `CompilerThreadStackSize` is set to 2048, whereas JDK 8 originally sets it to `0`. This change to 2048 was introduced in JDK-8140520. Since JDK-8140520 is likely not directly related to this fix, I have excluded it from this fix and changed `CompilerThreadStackSize` to 2040.
> 
> 2. Bug Reproduction:
> The bug was successfully reproduced in Linux x86_64 with THP enabled (/sys/kernel/mm/transparent_hugepage/enabled = always).
> Reproduction was confirmed using the following dummy thread program:
> 
> public class ThreadStackHugePageTest {
>         public static void main(String[] args) {
>                 final int NUM_THREADS = 1000;
>                 final long SLEEP_SECONDS = 3600;
>                 final long SLEEP_MILISECONDS = SLEEP_SECONDS * 1000;
> 
>                 List<Thread> threads = new ArrayList<>();
> 
>                 for (int i = 0; i < NUM_THREADS; i++) {
>                         Runnable task = () -> {
>                                 try {
>                                         Thread.sleep(SLEEP_MILISECONDS);
>                                 } catch (InterruptedException e) {
>                                         Thread.currentThread().interrupt();
>                                 }
>                         };
> 
>                         Thread thread = new Thread(task);
>                         threads.add(thread);
> 
>                         thread.start();
>                 }
> 
>                 System.out.println("all threads are started");
> 
>                 for (Thread thread : threads) {
>                         try {
>                                 thread.join();
>                         } catch (InterruptedException e) {
>                                 Thread.currentThread().interrupt();
>                         }
>                 }
>         }
> }
> 
> The fix significantly reduces the number of anonymous regions with fully occupied RSS.
> 
> 3. Regression Testing:
> I ran the test/hotspot tests on Linux x64 as a regression test. No failures were found.
> 
> Thank you.

Would anyone review this fix, please?

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PR Comment: https://git.openjdk.org/jdk8u-dev/pull/746#issuecomment-3905932529