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    SubjectRe: [genirq] cbe16f35be: will-it-scale.per_thread_ops -5.2% regression
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    On Tue, Apr 27 2021 at 13:42, Thomas Gleixner wrote:
    > On Tue, Apr 27 2021 at 17:00, kernel test robot wrote:
    >> FYI, we noticed a -5.2% regression of will-it-scale.per_thread_ops due to commit:
    >>
    >> commit: cbe16f35bee6880becca6f20d2ebf6b457148552 ("genirq: Add IRQF_NO_AUTOEN for request_irq/nmi()")
    >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
    >
    > this is the second report in the last week which makes not a lot of sense.
    > And this oneis makes absolutely no sense at all.
    >
    > This commit affects request_irq() and the related variants and has
    > exactly ZERO influence on anything related to that test case simply
    > because.
    >
    > I seriously have to ask the question whether this test infrastructure is
    > actually measuring what it claims to measure.
    >
    > As this commit clearly _cannot_ have the 'measured' side effect, this
    > points to some serious issue in the tests or the test infrastructure
    > itself.

    Just to illustrate the issue:

    I ran the will-it-scale getppid1 test manually against plain v5.12 and
    against v5.12 + cherrypicked cbe16f35be, i.e. the "offending" commit.

    The result for a full run is just in the noise:

    average: < 0.1%
    minimum: -0.22%
    maximum: 0.29%

    IOW very far away from -5.2%.

    That's an order of magnitude off.

    And no, I'm not going to run that lkp-test muck simply because it's
    unusable and the test result of will-it-scale itself is clear enough.

    Thanks,

    tglx

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