[igt-dev] [PATCH i-g-t v4 05/17] i915/perf: Account for OA sampling interval in polling test

[Lionel Landwerlin]

On 23/09/2022 22:52, Umesh Nerlige Ramappa wrote:
> The polling test reads all the reports and then expects EAGAIN on a
> subsequent read since it has consumed all available data. This
> works well for OA sampling periods in the order of 10s of ms. For
> smaller sampling periods like 500 us, we end up reading valid data and
> the test fails. Fix the check to account for the OA sampling period.
>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>

Yeah this is tough to test ...

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

> ---
>   tests/i915/perf.c | 16 ++++++++++++----
>   1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/tests/i915/perf.c b/tests/i915/perf.c
> index ca3ccc17..5fe874c1 100644
> --- a/tests/i915/perf.c
> +++ b/tests/i915/perf.c
> @@ -2220,14 +2220,22 @@ test_polling(uint64_t requested_oa_period, bool set_kernel_hrtimer, uint64_t ker
>   			n_extra_iterations++;
>   
>   		/* At this point, after consuming pending reports (and hoping
> -		 * the scheduler hasn't stopped us for too long we now
> -		 * expect EAGAIN on read.
> +		 * the scheduler hasn't stopped us for too long) we now expect
> +		 * EAGAIN on read. While this works most of the times, there are
> +		 * some rare failures when the OA period passed to this test is
> +		 * very small (say 500 us) and that results in some valid
> +		 * reports here. To weed out those rare occurences we assert
> +		 * only if the OA period is >= 40 ms because 40 ms has withstood
> +		 * the test of time on most platforms (ref: subtest: polling).
>   		 */
>   		while ((ret = read(stream_fd, buf, sizeof(buf))) < 0 &&
>   		       errno == EINTR)
>   			;
> -		igt_assert_eq(ret, -1);
> -		igt_assert_eq(errno, EAGAIN);
> +
> +		if (requested_oa_period >= 40000000) {
> +			igt_assert_eq(ret, -1);
> +			igt_assert_eq(errno, EAGAIN);
> +		}
>   
>   		n++;
>   	}