[igt-dev] [PATCH i-g-t] tests/perf: dramatically loosen expectations on oa-exponents

[Chris Wilson]

Quoting Lionel Landwerlin (2020-03-30 13:48:34)
> This test really quite flaky because it expects HW to emit reports
> following pretty much exactly the specified timer. And there are lots
> of reasons the HW might not be able to meet the timer deadline. The
> design is such that it's expected to not always meet the timer.
> 
> We just want to verify that the HW was configured properly, so loosen
> the checks to half the reports (of 30) meeting the timer deadline.
> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> ---
>  tests/perf.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/perf.c b/tests/perf.c
> index 442d89fb..023829fc 100644
> --- a/tests/perf.c
> +++ b/tests/perf.c
> @@ -1742,8 +1742,14 @@ test_oa_exponents(void)
>  
>                 igt_debug("matches=%u/%u\n", matches, n_timer_reports - 1);
>  
> -               /* Allow for a couple of errors. */
> -               igt_assert_lte(n_timer_reports - 3, matches);
> +               /*
> +                * Expect half the reports to match the timing
> +                * expectation. The results are quite erratic because
> +                * the condition under which the HW reaches
> +                * expectations depends on memory controller pressure
> +                * etc...
> +                */
> +               igt_assert_lte(n_timer_reports / 2, matches);

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

This will check for gross errors and so detect if we misconfigure the
HW.

What you might like to try is to look at the distribution of intervals,
and compare the median against your expectations.
-Chris