RFR: 8335167: Test runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved [v2]

[David Holmes]

On Mon, 2 Sep 2024 07:53:01 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> The test program runs once with PreTouch and another without PreTouch stacks. For each run the amounts of reserved and committed stack regions are held and then compared the ratio of with and without PreTouch. The ratio of PreTouch test should be greater than the other (because there will be higher committed regions due to pre-touching the pages).
>> 
>> In other words, the old version of this test ran two tests: 1) `preTouchTest` and 2) `noPreTouchTest` and extracted the amount of reserved and committed memory for stack. The ratio of the committed to reserved for preTouchTest ($ratio = \frac{committed}{reserved}$) is expected to be high (>75%) and for the noPreTouchTest is expected to be small (<50%). These expected amounts are not robust for all cases and resulted in 8335167.
>> 
>> In this PR, only one test is run with two sets of options for preTouch and noPreTouch stack memory. The amount of reserved and committed are stored after each run and the ratio of two runs are compared. It is expected that the preTouch has a greater ratio than the noPreTouch (`preTouch.ratio > noPreTouch.ratio`). 
>> 
>> ### Tests
>> The specific test is run on linux-x64, windows-x64 and macosx-aarch64 in tiers1-5 (100+ times).
>
> Afshin Zafari has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'origin/master' into _8335167_higher_ratio_commit
>  - 8335167: Test runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved
>  - 8335167: Test runtime/Thread/TestAlwaysPreTouchStacks.java failed with Expected a higher ratio between stack committed and reserved

Thanks for clarifying. If @tstuefe is okay with this proposed change in the logic then I am okay with it.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20531#pullrequestreview-2291454244