[igt-dev] [Intel-gfx] [PATCH i-g-t 2/2] igt/perf_pmu: Improve the presentation of the accuracy calibration

[Tvrtko Ursulin]

On 08/08/2018 15:59, Chris Wilson wrote:
> Normalize the variance to stddev, and remove some redundant steps in
> computing the time from itself.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>   tests/perf_pmu.c | 22 +++++++++++++---------
>   1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
> index 5a26d5272..4e8da3d94 100644
> --- a/tests/perf_pmu.c
> +++ b/tests/perf_pmu.c
> @@ -1577,8 +1577,8 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
>   		/* 1st pass is calibration, second pass is the test. */
>   		for (int pass = 0; pass < ARRAY_SIZE(timeout); pass++) {
>   			unsigned int target_idle_us = idle_us;
> -			uint64_t busy_ns = 0, idle_ns = 0;
>   			struct timespec start = { };
> +			uint64_t busy_ns = 0;
>   			unsigned long pass_ns = 0;
>   			double avg = 0.0, var = 0.0;
>   			unsigned int n = 0;
> @@ -1589,6 +1589,7 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
>   				unsigned long loop_ns, loop_busy;
>   				struct timespec _ts = { };
>   				double err, tmp;
> +				uint64_t now;
>   
>   				/* PWM idle sleep. */
>   				_ts.tv_nsec = target_idle_us * 1000;
> @@ -1605,14 +1606,13 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
>   				igt_spin_batch_end(spin);
>   
>   				/* Time accounting. */
> -				loop_ns = igt_nsec_elapsed(&start);
> -				loop_busy = loop_ns - loop_busy;
> -				loop_ns -= pass_ns;
> +				now = igt_nsec_elapsed(&start);
> +				loop_busy = now - loop_busy;
> +				loop_ns = now - pass_ns;
> +				pass_ns = now;
>   
>   				busy_ns += loop_busy;
>   				total_busy_ns += loop_busy;
> -				idle_ns += loop_ns - loop_busy;
> -				pass_ns += loop_ns;
>   				total_ns += loop_ns;

Looks okay, but ugh... just made me lose ten minutes reconstructing 
before and after for no real benefit. :I

>   
>   				/* Re-calibrate. */
> @@ -1628,10 +1628,14 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
>   				var += (err - avg) * (err - tmp);
>   			} while (pass_ns < timeout[pass]);
>   
> +			pass_ns = igt_nsec_elapsed(&start);
>   			expected = (double)busy_ns / pass_ns;
> -			igt_info("%u: busy %"PRIu64"us, idle %"PRIu64"us -> %.2f%% (target: %lu%%; average=%.2f, variance=%f)\n",
> -				 pass, busy_ns / 1000, idle_ns / 1000,
> -				 100 * expected, target_busy_pct, avg, var / n);
> +
> +			igt_info("%u: busy %"PRIu64"us, idle %"PRIu64"us -> %.2f%% (target: %lu%%; average=%.2f±%.3f%%)\n",
> +				 pass, busy_ns / 1000, (pass_ns - busy_ns) / 1000,
> +				 100 * expected, target_busy_pct,
> +				 avg, sqrt(var / n));
> +
>   			write(link[1], &expected, sizeof(expected));
>   		}
>   
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko