[Intel-gfx] [PATCH igt] igt/perf_pmu: Tweak wait_for_rc6, yet again

[Tvrtko Ursulin]

On 06/12/2017 23:12, Chris Wilson wrote:
> Still CI remains obstinate that RC6 is not smoothly incrementing during
> the sample period. Tweak the wait_for_rc6() to first wait for the
> initial Evaluation Interval before polling.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>   tests/perf_pmu.c         | 15 +++++++++++----
>   tests/pm_rc6_residency.c | 15 +++++++++++----
>   2 files changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
> index ff6568221..917832d1b 100644
> --- a/tests/perf_pmu.c
> +++ b/tests/perf_pmu.c
> @@ -1000,13 +1000,20 @@ static bool wait_for_rc6(int fd)
>   	struct timespec tv = {};
>   	uint64_t start, now;
>   
> -	start = pmu_read_single(fd);
> +	/* First wait for roughly an RC6 Evaluation Interval */
> +	usleep(160 * 1000);
> +
> +	/* Then poll for RC6 to start ticking */
> +	now = pmu_read_single(fd);
>   	do {
> -		usleep(50);
> +		start = now;
> +		usleep(5000);
>   		now = pmu_read_single(fd);
> -	} while (start == now && !igt_seconds_elapsed(&tv));
> +		if (now - start > 2e6)
> +			return true;

What is the thinking behind the 2ms of RC6 after 5ms of sleep criteria?

Regards,

Tvrtko

> +	} while (!igt_seconds_elapsed(&tv));
>   
> -	return start != now;
> +	return false;
>   }
>   
>   static void
> diff --git a/tests/pm_rc6_residency.c b/tests/pm_rc6_residency.c
> index 16f4b1421..7cc62dac8 100644
> --- a/tests/pm_rc6_residency.c
> +++ b/tests/pm_rc6_residency.c
> @@ -170,13 +170,20 @@ static bool wait_for_rc6(void)
>   	struct timespec tv = {};
>   	unsigned long start, now;
>   
> -	start = read_rc6_residency("rc6");
> +	/* First wait for roughly an RC6 Evaluation Interval */
> +        usleep(160 * 1000);
> +
> +        /* Then poll for RC6 to start ticking */
> +	now = read_rc6_residency("rc6");
>   	do {
> -		usleep(50);
> +		start = now;
> +		usleep(5000);
>   		now = read_rc6_residency("rc6");
> -	} while (now == start && !igt_seconds_elapsed(&tv));
> +		if (now - start > 2)
> +			return true;
> +	} while (!igt_seconds_elapsed(&tv));
>   
> -	return now != start;
> +	return false;
>   }
>   
>   igt_main
>