[igt-dev] [PATCH i-g-t v2] tests/perf_pmu: Avoid RT thread for accuracy test
Tvrtko Ursulin
tursulin at ursulin.net
Tue Apr 3 12:38:25 UTC 2018
From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Realtime scheduling interferes with execlists submission (tasklet) so try
to simplify the PWM loop in a few ways:
* Drop RT.
* Longer batches for smaller systematic error.
* More truthful test duration calculation.
* Less clock queries.
* No self-adjust - instead just report the achieved cycle and let the
parent check against it.
* Report absolute cycle error.
v2:
* Bring back self-adjust. (Chris Wilson)
(But slightly fixed version with no overflow.)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
tests/perf_pmu.c | 97 +++++++++++++++++++++++++-------------------------------
1 file changed, 43 insertions(+), 54 deletions(-)
diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
index f27b7ec7d2c2..0cfacd4a8fbe 100644
--- a/tests/perf_pmu.c
+++ b/tests/perf_pmu.c
@@ -1504,12 +1504,6 @@ test_enable_race(int gem_fd, const struct intel_execution_engine2 *e)
gem_quiescent_gpu(gem_fd);
}
-static double __error(double val, double ref)
-{
- igt_assert(ref > 1e-5 /* smallval */);
- return (100.0 * val / ref) - 100.0;
-}
-
static void __rearm_spin_batch(igt_spin_t *spin)
{
const uint32_t mi_arb_chk = 0x5 << 23;
@@ -1532,13 +1526,12 @@ static void
accuracy(int gem_fd, const struct intel_execution_engine2 *e,
unsigned long target_busy_pct)
{
- const unsigned int min_test_loops = 7;
- const unsigned long min_test_us = 1e6;
- unsigned long busy_us = 2500;
+ 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;
- unsigned long pwm_calibration_us;
- unsigned long test_us;
+ const unsigned long min_test_us = 1e6;
+ const unsigned long pwm_calibration_us = min_test_us;
+ const unsigned long test_us = min_test_us;
double busy_r, expected;
uint64_t val[2];
uint64_t ts[2];
@@ -1553,13 +1546,6 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
idle_us *= 2;
}
- pwm_calibration_us = min_test_loops * (busy_us + idle_us);
- while (pwm_calibration_us < min_test_us)
- pwm_calibration_us += busy_us + idle_us;
- test_us = min_test_loops * (idle_us + busy_us);
- while (test_us < min_test_us)
- test_us += busy_us + idle_us;
-
igt_info("calibration=%lums, test=%lums; ratio=%.2f%% (%luus/%luus)\n",
pwm_calibration_us / 1000, test_us / 1000,
(double)busy_us / (busy_us + idle_us) * 100.0,
@@ -1572,20 +1558,11 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
/* Emit PWM pattern on the engine from a child. */
igt_fork(child, 1) {
- struct sched_param rt = { .sched_priority = 99 };
const unsigned long timeout[] = {
pwm_calibration_us * 1000, test_us * 1000
};
- uint64_t total_busy_ns = 0, total_idle_ns = 0;
+ uint64_t total_busy_ns = 0, total_ns = 0;
igt_spin_t *spin;
- int ret;
-
- /* We need the best sleep accuracy we can get. */
- ret = sched_setscheduler(0,
- SCHED_FIFO | SCHED_RESET_ON_FORK,
- &rt);
- if (ret)
- igt_warn("Failed to set scheduling policy!\n");
/* Allocate our spin batch and idle it. */
spin = igt_spin_batch_new(gem_fd, 0, e2ring(gem_fd, e), 0);
@@ -1594,39 +1571,51 @@ 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++) {
- uint64_t busy_ns = -total_busy_ns;
- uint64_t idle_ns = -total_idle_ns;
- struct timespec test_start = { };
+ unsigned int target_idle_us = idle_us;
+ uint64_t busy_ns = 0, idle_ns = 0;
+ struct timespec start = { };
+ unsigned long pass_ns = 0;
+
+ igt_nsec_elapsed(&start);
- igt_nsec_elapsed(&test_start);
do {
- unsigned int target_idle_us, t_busy;
+ unsigned long loop_ns, loop_busy;
+ struct timespec _ts = { };
+ double err;
+
+ /* PWM idle sleep. */
+ _ts.tv_nsec = target_idle_us * 1000;
+ nanosleep(&_ts, NULL);
/* Restart the spinbatch. */
__rearm_spin_batch(spin);
__submit_spin_batch(gem_fd, spin, e, 0);
- /*
- * Note that the submission may be delayed to a
- * tasklet (ksoftirqd) which cannot run until we
- * sleep as we hog the cpu (we are RT).
- */
-
- t_busy = measured_usleep(busy_us);
+ /* PWM busy sleep. */
+ loop_busy = igt_nsec_elapsed(&start);
+ _ts.tv_nsec = busy_us * 1000;
+ nanosleep(&_ts, NULL);
igt_spin_batch_end(spin);
- gem_sync(gem_fd, spin->handle);
-
- total_busy_ns += t_busy;
-
- target_idle_us =
- (100 * total_busy_ns / target_busy_pct - (total_busy_ns + total_idle_ns)) / 1000;
- total_idle_ns += measured_usleep(target_idle_us);
- } while (igt_nsec_elapsed(&test_start) < timeout[pass]);
-
- busy_ns += total_busy_ns;
- idle_ns += total_idle_ns;
- expected = (double)busy_ns / (busy_ns + idle_ns);
+ /* Time accounting. */
+ loop_ns = igt_nsec_elapsed(&start);
+ loop_busy = loop_ns - loop_busy;
+ loop_ns -= pass_ns;
+
+ busy_ns += loop_busy;
+ total_busy_ns += loop_busy;
+ idle_ns += loop_ns - loop_busy;
+ pass_ns += loop_ns;
+ total_ns += loop_ns;
+
+ /* Re-calibrate. */
+ err = (double)total_busy_ns / total_ns -
+ (double)target_busy_pct / 100.0;
+ target_idle_us = (double)target_idle_us *
+ (1.0 + err);
+ } while (pass_ns < timeout[pass]);
+
+ expected = (double)busy_ns / pass_ns;
igt_info("%u: busy %"PRIu64"us, idle %"PRIu64"us: %.2f%% (target: %lu%%)\n",
pass, busy_ns / 1000, idle_ns / 1000,
100 * expected, target_busy_pct);
@@ -1655,8 +1644,8 @@ accuracy(int gem_fd, const struct intel_execution_engine2 *e,
busy_r = (double)(val[1] - val[0]) / (ts[1] - ts[0]);
- igt_info("error=%.2f%% (%.2f%% vs %.2f%%)\n",
- __error(busy_r, expected), 100 * busy_r, 100 * expected);
+ igt_info("error=%.2f (%.2f%% vs %.2f%%)\n",
+ (busy_r - expected) * 100, 100 * busy_r, 100 * expected);
assert_within(100.0 * busy_r, 100.0 * expected, 2);
}
--
2.14.1
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