tests/perf_pmu: More busy measurement tightening

Where we use measured sleeps, take PMU samples immediately before and
after and look at their delta in order to minimize the effect of any
test setup delays.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 28 insertions, 8 deletions

diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
index bf16e5e8..bdf452c8 100644
--- a/tests/perf_pmu.c
+++ b/tests/perf_pmu.c
@@ -145,8 +145,9 @@ single(int gem_fd, const struct intel_execution_engine2 *e, bool busy)
 	else
 		spin = NULL;
 
-	slept = measured_usleep(batch_duration_ns / 1000);
 	val = pmu_read_single(fd);
+	slept = measured_usleep(batch_duration_ns / 1000);
+	val = pmu_read_single(fd) - val;
 
 	igt_spin_batch_end(spin);
 	igt_spin_batch_free(gem_fd, spin);
@@ -180,8 +181,9 @@ busy_start(int gem_fd, const struct intel_execution_engine2 *e)
 
 	fd = open_pmu(I915_PMU_ENGINE_BUSY(e->class, e->instance));
 
-	slept = measured_usleep(batch_duration_ns / 1000);
 	val = pmu_read_single(fd);
+	slept = measured_usleep(batch_duration_ns / 1000);
+	val = pmu_read_single(fd) - val;
 
 	igt_spin_batch_free(gem_fd, spin);
 	close(fd);
@@ -227,8 +229,9 @@ busy_double_start(int gem_fd, const struct intel_execution_engine2 *e)
 	 */
 	fd = open_pmu(I915_PMU_ENGINE_BUSY(e->class, e->instance));
 
-	slept = measured_usleep(batch_duration_ns / 1000);
 	val = pmu_read_single(fd);
+	slept = measured_usleep(batch_duration_ns / 1000);
+	val = pmu_read_single(fd) - val;
 
 	igt_spin_batch_end(spin[0]);
 	igt_spin_batch_end(spin[1]);
@@ -279,6 +282,7 @@ busy_check_all(int gem_fd, const struct intel_execution_engine2 *e,
 	       const unsigned int num_engines)
 {
 	const struct intel_execution_engine2 *e_;
+	uint64_t tval[2][num_engines];
 	uint64_t val[num_engines];
 	int fd[num_engines];
 	unsigned long slept;
@@ -301,13 +305,17 @@ busy_check_all(int gem_fd, const struct intel_execution_engine2 *e,
 	igt_assert_eq(i, num_engines);
 
 	spin = igt_spin_batch_new(gem_fd, 0, e2ring(gem_fd, e), 0);
+	pmu_read_multi(fd[0], num_engines, tval[0]);
 	slept = measured_usleep(batch_duration_ns / 1000);
-	pmu_read_multi(fd[0], num_engines, val);
+	pmu_read_multi(fd[0], num_engines, tval[1]);
 
 	igt_spin_batch_end(spin);
 	igt_spin_batch_free(gem_fd, spin);
 	close(fd[0]);
 
+	for (i = 0; i < num_engines; i++)
+		val[i] = tval[1][i] - tval[0][i];
+
 	log_busy(num_engines, val);
 
 	assert_within_epsilon(val[busy_idx], slept, tolerance);
@@ -324,6 +332,7 @@ most_busy_check_all(int gem_fd, const struct intel_execution_engine2 *e,
 		    const unsigned int num_engines)
 {
 	const struct intel_execution_engine2 *e_;
+	uint64_t tval[2][num_engines];
 	uint64_t val[num_engines];
 	int fd[num_engines];
 	unsigned long slept;
@@ -362,13 +371,17 @@ most_busy_check_all(int gem_fd, const struct intel_execution_engine2 *e,
 	for (i = 0; i < num_engines; i++)
 		fd[i] = open_group(val[i], fd[0]);
 
+	pmu_read_multi(fd[0], num_engines, tval[0]);
 	slept = measured_usleep(batch_duration_ns / 1000);
-	pmu_read_multi(fd[0], num_engines, val);
+	pmu_read_multi(fd[0], num_engines, tval[1]);
 
 	igt_spin_batch_end(spin);
 	igt_spin_batch_free(gem_fd, spin);
 	close(fd[0]);
 
+	for (i = 0; i < num_engines; i++)
+		val[i] = tval[1][i] - tval[0][i];
+
 	log_busy(num_engines, val);
 
 	for (i = 0; i < num_engines; i++) {
@@ -384,6 +397,7 @@ static void
 all_busy_check_all(int gem_fd, const unsigned int num_engines)
 {
 	const struct intel_execution_engine2 *e;
+	uint64_t tval[2][num_engines];
 	uint64_t val[num_engines];
 	int fd[num_engines];
 	unsigned long slept;
@@ -418,13 +432,17 @@ all_busy_check_all(int gem_fd, const unsigned int num_engines)
 	for (i = 0; i < num_engines; i++)
 		fd[i] = open_group(val[i], fd[0]);
 
+	pmu_read_multi(fd[0], num_engines, tval[0]);
 	slept = measured_usleep(batch_duration_ns / 1000);
-	pmu_read_multi(fd[0], num_engines, val);
+	pmu_read_multi(fd[0], num_engines, tval[1]);
 
 	igt_spin_batch_end(spin);
 	igt_spin_batch_free(gem_fd, spin);
 	close(fd[0]);
 
+	for (i = 0; i < num_engines; i++)
+		val[i] = tval[1][i] - tval[0][i];
+
 	log_busy(num_engines, val);
 
 	for (i = 0; i < num_engines; i++)
@@ -765,13 +783,15 @@ multi_client(int gem_fd, const struct intel_execution_engine2 *e)
 	spin = igt_spin_batch_new(gem_fd, 0, e2ring(gem_fd, e), 0);
 	igt_spin_batch_set_timeout(spin, 2 * batch_duration_ns);
 
-	slept = measured_usleep(batch_duration_ns / 1000);
+	val[0] = pmu_read_single(fd[0]);
 	val[1] = pmu_read_single(fd[1]);
+	slept = measured_usleep(batch_duration_ns / 1000);
+	val[1] = pmu_read_single(fd[1]) - val[1];
 	close(fd[1]);
 
 	gem_sync(gem_fd, spin->handle);
 
-	val[0] = pmu_read_single(fd[0]);
+	val[0] = pmu_read_single(fd[0]) - val[0];
 
 	igt_spin_batch_free(gem_fd, spin);
 	close(fd[0]);