RFR: 8324781: runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved [v9]

[Patrick Zhang]

On Mon, 6 May 2024 03:33:30 GMT, Liming Liu <duke at openjdk.org> wrote:

>> 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 versions of kernels first, and checking the availability of MADV_POPULATE_WRITE when they are not older than 5.14.
>
> Liming Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix the wrong condition

To clarify, the current revised patch does **NOT** add any if-cond to check UEK, instead it enhances the check of the readiness of `MADV_POPULATE_WRITE` on `5.14 and beyond` (stated by Linux kernel official docs). In addition, the two test cases failing on UEK kernel can also be a justification that the condition of having `supportMadvPopulateWrite` needs to be strengthened. We could not say that it is a problem only exists in UEK kernel, in theory every distros could backport part of `MADV_POPULATE_WRITE` function from 5.14 to previous version or reuse any madv op code there, which is out of our control or our testing coverage. 

Therefore, having the >=5.14 check can be a safer way to all.

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PR Comment: https://git.openjdk.org/jdk/pull/18592#issuecomment-2151650235