[Bug 104013] [CI] igt at perf_pmu@semaphore-wait-[vcs0|vecs0|bcs0] - Failed assertion: (double)(val[1] - val[0]) <= (1.0 + (tolerance)) * (double)(slept) && (double)(val[1] - val[0]) >= (1.0 - (tolerance)) * (double)(slept)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=104013

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit c7b20c950276a41badd994324e1983760e44842b
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Sat Dec 2 00:14:52 2017 +0000

    igt/perf_pmu: Tighten semaphore-wait measurement

    Record the before/after semaphore-wait values around the sleep to try to
    reduce the inaccuracy from scheduler delays. Previously, the samples
    were taken before submitting the batch and then after synchronising its
    completion. The measurement will then be the total that the semaphore
    was being sampled, but with the extra syscalls intervening may have
    drifted from the sleep duration. To further reduce the disparity, wait
    for the batch to start executing before taking our samples.

    References: https://bugs.freedesktop.org/show_bug.cgi?id=104013
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
    Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Once again, hopefully the last tweak required.

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