[Intel-gfx] [PATCH i-g-t v4 11/12] tests/perf: estimate number of blocking/polling based on time spent

[Lionel Landwerlin]

Blocking & polling tests define an amount of time to spend in the test
and then estimate the number of syscalls that should successfully
return. The problem is that while running the test we might spend
slightly more time than initiallly planned. This change estimates the
number of syscalls based on time spent after the fact.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
---
 tests/perf.c | 42 +++++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/tests/perf.c b/tests/perf.c
index 24df7c2a..6c062d20 100644
--- a/tests/perf.c
+++ b/tests/perf.c
@@ -2372,7 +2372,8 @@ test_blocking(void)
 		DRM_I915_PERF_PROP_OA_EXPONENT, oa_exponent,
 	};
 	struct drm_i915_perf_open_param param = {
-		.flags = I915_PERF_FLAG_FD_CLOEXEC,
+		.flags = I915_PERF_FLAG_FD_CLOEXEC |
+			I915_PERF_FLAG_DISABLED,
 		.num_properties = sizeof(properties) / 16,
 		.properties_ptr = to_user_pointer(properties),
 	};
@@ -2397,16 +2398,17 @@ test_blocking(void)
 	 */
 	int min_iterations = (test_duration_ns / (oa_period + 6000000ull));
 
-	int64_t start;
+	int64_t start, end;
 	int n = 0;
 
 	stream_fd = __perf_open(drm_fd, &param);
 
 	times(&start_times);
 
-	igt_debug("tick length = %dns, test duration = %"PRIu64"ns, min iter. = %d, max iter. = %d\n",
+	igt_debug("tick length = %dns, test duration = %"PRIu64"ns, min iter. = %d,"
+		  " estimated max iter. = %d, oa_period = %"PRIu64"ns\n",
 		  (int)tick_ns, test_duration_ns,
-		  min_iterations, max_iterations);
+		  min_iterations, max_iterations, oa_period);
 
 	/* In the loop we perform blocking polls while the HW is sampling at
 	 * ~25Hz, with the expectation that we spend most of our time blocked
@@ -2425,8 +2427,13 @@ test_blocking(void)
 	 * floor(real_stime)).
 	 *
 	 * We Loop for 1000 x tick_ns so one tick corresponds to 0.1%
+	 *
+	 * Also enable the stream just before poll/read to minimize
+	 * the error delta.
 	 */
-	for (start = get_time(); (get_time() - start) < test_duration_ns; /* nop */) {
+	start = get_time();
+	do_ioctl(stream_fd, I915_PERF_IOCTL_ENABLE, 0);
+	for (/* nop */; ((end = get_time()) - start) < test_duration_ns; /* nop */) {
 		struct drm_i915_perf_record_header *header;
 		bool timer_report_read = false;
 		bool non_timer_report_read = false;
@@ -2468,6 +2475,12 @@ test_blocking(void)
 		n++;
 	}
 
+	/* Updated the maximum of iterations based on the time spent
+	 * in the loop.
+	 */
+	max_iterations = (end - start) / oa_period + 1;
+	igt_debug("adjusted max iter. = %d\n", max_iterations);
+
 	times(&end_times);
 
 	/* Using nanosecond units is fairly silly here, given the tick in-
@@ -2524,6 +2537,7 @@ test_polling(void)
 	};
 	struct drm_i915_perf_open_param param = {
 		.flags = I915_PERF_FLAG_FD_CLOEXEC |
+			I915_PERF_FLAG_DISABLED |
 			I915_PERF_FLAG_FD_NONBLOCK,
 		.num_properties = sizeof(properties) / 16,
 		.properties_ptr = to_user_pointer(properties),
@@ -2548,7 +2562,7 @@ test_polling(void)
 	 * to check for data and giving some time to read().
 	 */
 	int min_iterations = (test_duration_ns / (oa_period + 6000000ull));
-	int64_t start;
+	int64_t start, end;
 	int n = 0;
 
 	stream_fd = __perf_open(drm_fd, &param);
@@ -2576,8 +2590,13 @@ test_polling(void)
 	 * floor(real_stime)).
 	 *
 	 * We Loop for 1000 x tick_ns so one tick corresponds to 0.1%
+	 *
+	 * Also enable the stream just before poll/read to minimize
+	 * the error delta.
 	 */
-	for (start = get_time(); (get_time() - start) < test_duration_ns; /* nop */) {
+	start = get_time();
+	do_ioctl(stream_fd, I915_PERF_IOCTL_ENABLE, 0);
+	for (/* nop */; ((end = get_time()) - start) < test_duration_ns; /* nop */) {
 		struct pollfd pollfd = { .fd = stream_fd, .events = POLLIN };
 		struct drm_i915_perf_record_header *header;
 		bool timer_report_read = false;
@@ -2625,8 +2644,7 @@ test_polling(void)
 				if (header->type == DRM_I915_PERF_RECORD_SAMPLE) {
 					uint32_t *report = (void *)(header + 1);
 
-					if (oa_report_is_periodic(oa_exponent,
-								  report))
+					if (oa_report_is_periodic(oa_exponent, report))
 						timer_report_read = true;
 					else
 						non_timer_report_read = true;
@@ -2650,6 +2668,12 @@ test_polling(void)
 		n++;
 	}
 
+	/* Updated the maximum of iterations based on the time spent
+	 * in the loop.
+	 */
+	max_iterations = (end - start) / oa_period + 1;
+	igt_debug("adjusted max iter. = %d\n", max_iterations);
+
 	times(&end_times);
 
 	/* Using nanosecond units is fairly silly here, given the tick in-
-- 
2.14.1