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8324781: runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved #18417

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@limingliu-ampere limingliu-ampere commented Mar 21, 2024

The testcase failed on Oracle CI since JDK-8315923. The root cause is that Oracle CI runs Linux-5.4.17-UEK where the value of MADV_POPULATE_WRITE (23) is used as MADV_DONTEXEC which is not supported by upstream. This PR solves the testcase failure by checking the support of (MADV_POPULATE_WRITE_value + 1) for UEK releases.


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Issues

  • JDK-8324781: runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved (Bug - P2)
  • JDK-8325218: gc/parallel/TestAlwaysPreTouchBehavior.java fails (Bug - P3)

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bridgekeeper bot commented Mar 21, 2024

👋 Welcome back limingliu-ampere! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

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❗ This change is not yet ready to be integrated.
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/issue add 8325218

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openjdk bot commented Mar 21, 2024

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Adding additional issue to issue list: 8325218: gc/parallel/TestAlwaysPreTouchBehavior.java fails.

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@limingliu-ampere The following label will be automatically applied to this pull request:

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@limingliu-ampere Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

@openjdk openjdk bot added the rfr Pull request is ready for review label Mar 21, 2024
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mlbridge bot commented Mar 21, 2024

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Comment on lines +4850 to +4852
// See https://github.com/oracle/linux-uek/issues/23
const int flag = MADV_POPULATE_WRITE + (os::Linux::_is_uek_release ? 1 : 0);
FLAG_SET_DEFAULT(UseMadvPopulateWrite, (::madvise(0, 0, flag) == 0));
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I read the supporting material and I still can't get this sorted in my head. From my reading some UEK versions have this problem and some do not. But you do this "trick" for all UEK versions and I just don't understand how that works. ??

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Personally, I think it is safe to check 24 for all UEK versions:

  • for versions prior to 5.15 UEK, 23 is supported as MADV_DONTEXEC, while 24 is not supported;
  • for 5.15 (, 5.16 and 5.17 if existed) UEK, 23 is supported as MADV_POPULATE_WRITE, while 24 is supported as MADV_DOEXEC;
  • for 5.18 UEK or newer, both 23 and 24 are supported as the same functions as upstream.

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So what is the affect of using MADV_DOEXEC when the intent was to use MADV_POPULATE_WRITE?

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MADV_DOEXEC is not used in os::pd_pretouch_memory, but just used in os::init_2 for 5.15 UEK. The key is MADV_POPULATE_WRITE is supported as 23 on UEK releases if and only if 24 is supported. If the code is confusing, I will check whether the version of kernel is newer than 5.14 here rather than checking the support of 24.

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/withdraw

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@limingliu-ampere Unknown command withdraw - for a list of valid commands use /help.

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/help

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tstuefe commented May 22, 2024

Please reopen this, and just run the test with -XX:-UseMadvPopulateWrite. That should solve the problem for the test, no?

The test's purpose is not to test Oracle Linux' inability to handle madvise flags correctly but to test -XX:+AlwaysPreTouchStacks.

We can and should deal with the Oracle Linux problem independently (Note that I reported the problem to Oracle secalert back in March, and they promised a kernel fix).

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stefank commented May 22, 2024

Please reopen this, and just run the test with -XX:-UseMadvPopulateWrite. That should solve the problem for the test, no?

The test's purpose is not to test Oracle Linux' inability to handle madvise flags correctly but to test -XX:+AlwaysPreTouchStacks.

We can and should deal with the Oracle Linux problem independently (Note that I reported the problem to Oracle secalert back in March, and they promised a kernel fix).

This is being dealt with in #18592, right? (Which I now see needs to be sponsored)

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