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List:       openjdk-hotspot-runtime-dev
Subject:    Re: RFR: 8324776: runtime/os/TestTransparentHugePageUsage.java fails with The usage of THP is not en
From:       Thomas Stuefe <stuefe () openjdk ! org>
Date:       2024-04-27 5:59:08
Message-ID: u6uKx4dOzhlCreNyHDASfW6WSzbzH7jWiVGM9lInH20=.04e51964-aadd-44a7-96b7-ab8040499934 () github ! com
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On Tue, 16 Apr 2024 08:57:48 GMT, Liming Liu <duke@openjdk.org> wrote:

> This PR remove the testcase introduced in JDK-8315923, as we could not find a \
> reliable way to evaluate the usage of THP. We have tried the following methods: 
> 1. transverse /proc/self/smaps rather than looking up the first map covered by the \
> heap, as we found there can be multiple sections in /proc/self/smaps for the heap; \
> (https://github.com/limingliu-ampere/jdk/commit/c5b0c4cdf9fa42988faa9fee6ee004ebb599d40a)
>  2. take the mode of de-fragment and the enabling of khugepaged into account rather \
> than just THP mode, as THP may not be available immediately when the de-fragment \
> mode is neither "always" nor "madvise", or khugepaged does not collapse pages; \
> (https://github.com/limingliu-ampere/jdk/commit/9c70e9384325b44e074a9e8973846343b27fd2cc)
>  3. call madvise with MADV_HUGEPAGE unconditionally rather than calling it only \
> when THP mode is not "always", and adjust the sizes of young and old generations to \
> ensure the parameters are aligned with THP; \
> (https://github.com/limingliu-ampere/jdk/commit/de9607ff64cc526bca9968b72a7065888c2f944d)
>  4. check the changes of system-wide counters like thp_* in /proc/vmstat before and \
> after pretouch via gtest. \
> (https://github.com/limingliu-ampere/jdk/commit/bc83e19a682156ee7d09bf939c2b18f3d8c79e22)
>  
> But none of them helps. The amount of THP keeps zero on Oracle CI, although the THP \
> mode is "always", the de-fragment mode is "madvise" and khugepaged is enabled. \
> Furthermore, none of thp counters changed around pretouch. However, we tried the \
> same kernel (5.15-UEK) as Oracle CI on our machine, and found that these methods do \
> help. Thus, we decided to remove this testcase.

I am fine with removing the test case. There is a point of diminishing returns, and \
you did your due diligence here.

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

Marked as reviewed by stuefe (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18792#pullrequestreview-2026357511


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