[PATCH i-g-t] igt/gem_exec_latency: Report stddev for rthog

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

Report and compare stddev instead of variance so that direct submission
passes ;)
---
 tests/gem_exec_latency.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/tests/gem_exec_latency.c b/tests/gem_exec_latency.c
index 547d728b3..757b390d0 100644
--- a/tests/gem_exec_latency.c
+++ b/tests/gem_exec_latency.c
@@ -429,7 +429,7 @@ rthog_latency_on_ring(int fd, unsigned int ring, const char *name)
 					igt_warn("Failed to set scheduling policy!\n");
 					msg.status = RT_FAIL;
 					write(link[1], &msg, sizeof(msg));
-					exit(1);
+					break;
 				}
 			}
 
@@ -439,7 +439,7 @@ rthog_latency_on_ring(int fd, unsigned int ring, const char *name)
 					 passname[pass]);
 				msg.status = RT_FAIL;
 				write(link[1], &msg, sizeof(msg));
-				exit(1);
+				break;
 			}
 			igt_spin_busywait_until_running(spin);
 
@@ -457,7 +457,7 @@ rthog_latency_on_ring(int fd, unsigned int ring, const char *name)
 					igt_warn("Wait timeout! (%s)\n",
 						 passname[pass]);
 					write(link[1], &msg, sizeof(msg));
-					exit(1);
+					break;
 				}
 
 				if (t > msg.max)
@@ -468,17 +468,15 @@ rthog_latency_on_ring(int fd, unsigned int ring, const char *name)
 
 			igt_spin_batch_free(fd, spin);
 
-			igt_info("%10s: mean=%.2fus variance=%.2fus max=%.2fus (n=%lu)\n",
+			igt_info("%10s: mean=%.2fus stddev=%.3fus max=%.2fus (n=%lu)\n",
 				 passname[pass],
 				 igt_mean_get(&msg.mean) * 1e6,
-				 igt_mean_get_variance(&msg.mean) * 1e6,
+				 sqrt(igt_mean_get_variance(&msg.mean)) * 1e6,
 				 msg.max * 1e6,
 				 msg.mean.count);
 
 			write(link[1], &msg, sizeof(msg));
 		} while (++pass < 3);
-
-		exit(0);
 	}
 
 	for (i = 0; i < 3; i++) {
@@ -494,11 +492,12 @@ rthog_latency_on_ring(int fd, unsigned int ring, const char *name)
 	igt_waitchildren();
 
 	/*
-	 * Check that the submission latency variance for a task with RT
-	 * priority is no larger than three times the same of a normal task.
+	 * Check that the submission latency stddev for a task with RT
+	 * priority is no larger than three times the same of a normal task,
+	 * (since variance is the square of stddev, we check 9 times)
 	 */
 	igt_assert(igt_mean_get_variance(&res[2].mean) <
-		   igt_mean_get_variance(&res[1].mean) * 3);
+		   igt_mean_get_variance(&res[1].mean) * 9);
 }
 
 igt_main
-- 
2.17.0

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