On 10/08/2018 14:25, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2018-08-09 12:54:41)
On 08/08/2018 15:59, Chris Wilson wrote:
Our observation is that the systematic error is proportional to the
number of iterations we perform; the suspicion is that it directly
correlates with the number of sleeps. Reduce the number of iterations,
to try and keep the error in check.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
tests/perf_pmu.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
index 9a20abb6b..5a26d5272 100644
--- a/tests/perf_pmu.c
+++ b/tests/perf_pmu.c
@@ -1521,14 +1521,13 @@ static void __rearm_spin_batch(igt_spin_t *spin)
static void
accuracy(int gem_fd, const struct intel_execution_engine2 *e,
- unsigned long target_busy_pct)
+ unsigned long target_busy_pct,
+ unsigned long target_iters)
{
- unsigned long busy_us = 10000 - 100 * (1 + abs(50 - target_busy_pct));
- unsigned long idle_us = 100 * (busy_us - target_busy_pct *
- busy_us / 100) / target_busy_pct;
const unsigned long min_test_us = 1e6;
- const unsigned long pwm_calibration_us = min_test_us;
- const unsigned long test_us = min_test_us;
+ unsigned long pwm_calibration_us;
+ unsigned long test_us;
+ unsigned long cycle_us, busy_us, idle_us;
double busy_r, expected;
uint64_t val[2];
uint64_t ts[2];
@@ -1538,18 +1537,27 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
/* Sampling platforms cannot reach the high accuracy criteria. */
igt_require(gem_has_execlists(gem_fd));
- while (idle_us < 2500) {
+ /* Aim for approximately 100 iterations for calibration */
+ cycle_us = min_test_us / target_iters;
+ busy_us = cycle_us * target_busy_pct / 100;
+ idle_us = cycle_us - busy_us;
2% load, 1s / 10 iters
cycles_us = 100ms
busy_us = 2ms
idle_us = 98ms
...
+
+ while (idle_us < 2500 || busy_us < 2500) {
busy_us *= 2;
idle_us *= 2;
...
busy_us = 4ms
idle_us = 196ms
Currently it is 250ms per 98:2 cycle and about 20ms per 50:50 cycle. So
we are only doing 4 and 50 iterations respectively.
10 cycles is strictly an improvement :-p
Hmm indeed. It seems I misremembered how it works. I'll re-read your
patches.
Regards,
Tvrtko
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