[PATCH i-g-t 08/15] tests/intel/xe_oa: blocking and polling tests
Ashutosh Dixit
ashutosh.dixit at intel.com
Fri Jul 5 21:43:09 UTC 2024
"blocking", "polling" and "polling-small-buf".
v2: Rename xe perf layer as xe observation layer
Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
---
tests/intel/xe_oa.c | 463 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 463 insertions(+)
diff --git a/tests/intel/xe_oa.c b/tests/intel/xe_oa.c
index 40bc0902dd..6dcf447e68 100644
--- a/tests/intel/xe_oa.c
+++ b/tests/intel/xe_oa.c
@@ -430,6 +430,24 @@ static struct drm_xe_engine_class_instance *oa_unit_engine(int fd, int n)
return hwe;
}
+static char *
+pretty_print_oa_period(uint64_t oa_period_ns)
+{
+ static char result[100];
+ static const char *units[4] = { "ns", "us", "ms", "s" };
+ double val = oa_period_ns;
+ int iter = 0;
+
+ while (iter < (ARRAY_SIZE(units) - 1) &&
+ val >= 1000.0f) {
+ val /= 1000.0f;
+ iter++;
+ }
+
+ snprintf(result, sizeof(result), "%.3f%s", val, units[iter]);
+ return result;
+}
+
static void
__perf_close(int fd)
{
@@ -1630,6 +1648,432 @@ static void test_invalid_oa_exponent(void)
}
}
+static int64_t
+get_time(void)
+{
+ struct timespec ts;
+
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+
+ return ts.tv_sec * 1000000000 + ts.tv_nsec;
+}
+
+/**
+ * SUBTEST: blocking
+ * Description: Test blocking reads
+ */
+/* Note: The interface doesn't currently provide strict guarantees or control
+ * over the upper bound for how long it might take for a POLLIN event after
+ * some OA report is written by the OA unit.
+ *
+ * The plan is to add a property later that gives some control over the maximum
+ * latency, but for now we expect it is tuned for a fairly low latency
+ * suitable for applications wanting to provide live feedback for captured
+ * metrics.
+ *
+ * At the time of writing this test the driver was using a fixed 200Hz hrtimer
+ * regardless of the OA sampling exponent.
+ *
+ * There is no lower bound since a stream configured for periodic sampling may
+ * still contain other automatically triggered reports.
+ *
+ * What we try and check for here is that blocking reads don't return EAGAIN
+ * and that we aren't spending any significant time burning the cpu in
+ * kernelspace.
+ */
+static void test_blocking(uint64_t requested_oa_period,
+ bool set_kernel_hrtimer,
+ uint64_t kernel_hrtimer,
+ const struct drm_xe_engine_class_instance *hwe)
+{
+ int oa_exponent = max_oa_exponent_for_period_lte(requested_oa_period);
+ uint64_t oa_period = oa_exponent_to_ns(oa_exponent);
+ uint64_t props[XE_OA_MAX_SET_PROPERTIES * 2];
+ uint64_t *idx = props;
+ struct intel_xe_oa_open_prop param;
+ uint8_t buf[1024 * 1024];
+ struct tms start_times;
+ struct tms end_times;
+ int64_t user_ns, kernel_ns;
+ int64_t tick_ns = 1000000000 / sysconf(_SC_CLK_TCK);
+ int64_t test_duration_ns = tick_ns * 100;
+ int max_iterations = (test_duration_ns / oa_period) + 2;
+ int n_extra_iterations = 0;
+ int perf_fd;
+
+ /* It's a bit tricky to put a lower limit here, but we expect a
+ * relatively low latency for seeing reports, while we don't currently
+ * give any control over this in the api.
+ *
+ * We assume a maximum latency of 6 millisecond to deliver a POLLIN and
+ * read() after a new sample is written (46ms per iteration) considering
+ * the knowledge that that the driver uses a 200Hz hrtimer (5ms period)
+ * to check for data and giving some time to read().
+ */
+ int min_iterations = (test_duration_ns / (oa_period + kernel_hrtimer + kernel_hrtimer / 5));
+ int64_t start, end;
+ int n = 0;
+ struct intel_xe_perf_metric_set *test_set = metric_set(hwe);
+ size_t format_size = get_oa_format(test_set->perf_oa_format).size;
+
+ ADD_PROPS(props, idx, SAMPLE_OA, true);
+ ADD_PROPS(props, idx, OA_METRIC_SET, test_set->perf_oa_metrics_set);
+ ADD_PROPS(props, idx, OA_FORMAT, __ff(test_set->perf_oa_format));
+ ADD_PROPS(props, idx, OA_PERIOD_EXPONENT, oa_exponent);
+ ADD_PROPS(props, idx, OA_DISABLED, true);
+ ADD_PROPS(props, idx, OA_UNIT_ID, 0);
+ ADD_PROPS(props, idx, OA_ENGINE_INSTANCE, hwe->engine_instance);
+
+ param.num_properties = (idx - props) / 2;
+ param.properties_ptr = to_user_pointer(props);
+
+ perf_fd = __perf_open(drm_fd, ¶m, true /* prevent_pm */);
+ set_fd_flags(perf_fd, O_CLOEXEC);
+
+ times(&start_times);
+
+ igt_debug("tick length = %dns, test duration = %"PRIu64"ns, min iter. = %d,"
+ " estimated max iter. = %d, oa_period = %s\n",
+ (int)tick_ns, test_duration_ns,
+ min_iterations, max_iterations,
+ pretty_print_oa_period(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
+ * in the kernel, and shouldn't be burning cpu cycles in the kernel in
+ * association with this process (verified by looking at stime before
+ * and after loop).
+ *
+ * We're looking to assert that less than 1% of the test duration is
+ * spent in the kernel dealing with polling and read()ing.
+ *
+ * The test runs for a relatively long time considering the very low
+ * resolution of stime in ticks of typically 10 milliseconds. Since we
+ * don't know the fractional part of tick values we read from userspace
+ * so our minimum threshold needs to be >= one tick since any
+ * measurement might really be +- tick_ns (assuming we effectively get
+ * 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.
+ */
+ start = get_time();
+ do_ioctl(perf_fd, DRM_XE_OBSERVATION_IOCTL_ENABLE, 0);
+ for (/* nop */; ((end = get_time()) - start) < test_duration_ns; /* nop */) {
+ bool timer_report_read = false;
+ bool non_timer_report_read = false;
+ int ret;
+
+ while ((ret = read(perf_fd, buf, sizeof(buf))) < 0 &&
+ (errno == EINTR || errno == EIO))
+ ;
+ igt_assert(ret > 0);
+
+ for (int offset = 0; offset < ret; offset += format_size) {
+ uint32_t *report = (void *)(buf + offset);
+
+ if (oa_report_is_periodic(oa_exponent, report))
+ timer_report_read = true;
+ else
+ non_timer_report_read = true;
+ }
+
+ if (non_timer_report_read && !timer_report_read)
+ n_extra_iterations++;
+
+ n++;
+ }
+
+ times(&end_times);
+
+ /* Using nanosecond units is fairly silly here, given the tick in-
+ * precision - ah well, it's consistent with the get_time() units.
+ */
+ user_ns = (end_times.tms_utime - start_times.tms_utime) * tick_ns;
+ kernel_ns = (end_times.tms_stime - start_times.tms_stime) * tick_ns;
+
+ igt_debug("%d blocking reads during test with %"PRIu64" Hz OA sampling (expect no more than %d)\n",
+ n, NSEC_PER_SEC / oa_period, max_iterations);
+ igt_debug("%d extra iterations seen, not related to periodic sampling (e.g. context switches)\n",
+ n_extra_iterations);
+ igt_debug("time in userspace = %"PRIu64"ns (+-%dns) (start utime = %d, end = %d)\n",
+ user_ns, (int)tick_ns,
+ (int)start_times.tms_utime, (int)end_times.tms_utime);
+ igt_debug("time in kernelspace = %"PRIu64"ns (+-%dns) (start stime = %d, end = %d)\n",
+ kernel_ns, (int)tick_ns,
+ (int)start_times.tms_stime, (int)end_times.tms_stime);
+
+ /* With completely broken blocking (but also not returning an error) we
+ * could end up with an open loop,
+ */
+ igt_assert(n <= (max_iterations + n_extra_iterations));
+
+ /* Make sure the driver is reporting new samples with a reasonably
+ * low latency...
+ */
+ igt_assert(n > (min_iterations + n_extra_iterations));
+
+ if (!set_kernel_hrtimer)
+ igt_assert(kernel_ns <= (test_duration_ns / 100ull));
+
+ __perf_close(perf_fd);
+}
+
+/**
+ * SUBTEST: polling
+ * Description: Test polled reads
+ */
+static void test_polling(uint64_t requested_oa_period,
+ bool set_kernel_hrtimer,
+ uint64_t kernel_hrtimer,
+ const struct drm_xe_engine_class_instance *hwe)
+{
+ int oa_exponent = max_oa_exponent_for_period_lte(requested_oa_period);
+ uint64_t oa_period = oa_exponent_to_ns(oa_exponent);
+ uint64_t props[XE_OA_MAX_SET_PROPERTIES * 2];
+ uint64_t *idx = props;
+ struct intel_xe_oa_open_prop param;
+ uint8_t buf[1024 * 1024];
+ struct tms start_times;
+ struct tms end_times;
+ int64_t user_ns, kernel_ns;
+ int64_t tick_ns = 1000000000 / sysconf(_SC_CLK_TCK);
+ int64_t test_duration_ns = tick_ns * 100;
+
+ int max_iterations = (test_duration_ns / oa_period) + 2;
+ int n_extra_iterations = 0;
+
+ /* It's a bit tricky to put a lower limit here, but we expect a
+ * relatively low latency for seeing reports.
+ *
+ * We assume a maximum latency of kernel_hrtimer + some margin
+ * to deliver a POLLIN and read() after a new sample is
+ * written (40ms + hrtimer + margin per iteration) considering
+ * the knowledge that that the driver uses a 200Hz hrtimer
+ * (5ms period) to check for data and giving some time to
+ * read().
+ */
+ int min_iterations = (test_duration_ns / (oa_period + (kernel_hrtimer + kernel_hrtimer / 5)));
+ int64_t start, end;
+ int n = 0;
+ struct intel_xe_perf_metric_set *test_set = metric_set(hwe);
+ size_t format_size = get_oa_format(test_set->perf_oa_format).size;
+
+ ADD_PROPS(props, idx, SAMPLE_OA, true);
+ ADD_PROPS(props, idx, OA_METRIC_SET, test_set->perf_oa_metrics_set);
+ ADD_PROPS(props, idx, OA_FORMAT, __ff(test_set->perf_oa_format));
+ ADD_PROPS(props, idx, OA_PERIOD_EXPONENT, oa_exponent);
+ ADD_PROPS(props, idx, OA_DISABLED, true);
+ ADD_PROPS(props, idx, OA_UNIT_ID, 0);
+ ADD_PROPS(props, idx, OA_ENGINE_INSTANCE, hwe->engine_instance);
+
+ param.num_properties = (idx - props) / 2;
+ param.properties_ptr = to_user_pointer(props);
+
+ stream_fd = __perf_open(drm_fd, ¶m, true /* prevent_pm */);
+ set_fd_flags(stream_fd, O_CLOEXEC | O_NONBLOCK);
+
+ times(&start_times);
+
+ igt_debug("tick length = %dns, oa period = %s, "
+ "test duration = %"PRIu64"ns, min iter. = %d, max iter. = %d\n",
+ (int)tick_ns, pretty_print_oa_period(oa_period), test_duration_ns,
+ min_iterations, max_iterations);
+
+ /* 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
+ * in the kernel, and shouldn't be burning cpu cycles in the kernel in
+ * association with this process (verified by looking at stime before
+ * and after loop).
+ *
+ * We're looking to assert that less than 1% of the test duration is
+ * spent in the kernel dealing with polling and read()ing.
+ *
+ * The test runs for a relatively long time considering the very low
+ * resolution of stime in ticks of typically 10 milliseconds. Since we
+ * don't know the fractional part of tick values we read from userspace
+ * so our minimum threshold needs to be >= one tick since any
+ * measurement might really be +- tick_ns (assuming we effectively get
+ * 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.
+ */
+ start = get_time();
+ do_ioctl(stream_fd, DRM_XE_OBSERVATION_IOCTL_ENABLE, 0);
+ for (/* nop */; ((end = get_time()) - start) < test_duration_ns; /* nop */) {
+ struct pollfd pollfd = { .fd = stream_fd, .events = POLLIN };
+ bool timer_report_read = false;
+ bool non_timer_report_read = false;
+ int ret;
+
+ while ((ret = poll(&pollfd, 1, -1)) < 0 && errno == EINTR)
+ ;
+ igt_assert_eq(ret, 1);
+ igt_assert(pollfd.revents & POLLIN);
+
+ while ((ret = read(stream_fd, buf, sizeof(buf))) < 0 &&
+ (errno == EINTR || errno == EIO))
+ ;
+
+ /* Don't expect to see EAGAIN if we've had a POLLIN event
+ *
+ * XXX: actually this is technically overly strict since we do
+ * knowingly allow false positive POLLIN events. At least in
+ * the future when supporting context filtering of metrics for
+ * Gen8+ handled in the kernel then POLLIN events may be
+ * delivered when we know there are pending reports to process
+ * but before we've done any filtering to know for certain that
+ * any reports are destined to be copied to userspace.
+ *
+ * Still, for now it's a reasonable sanity check.
+ */
+ if (ret < 0)
+ igt_debug("Unexpected error when reading after poll = %d\n", errno);
+ igt_assert_neq(ret, -1);
+
+ /* For Haswell reports don't contain a well defined reason
+ * field we so assume all reports to be 'periodic'. For gen8+
+ * we want to to consider that the HW automatically writes some
+ * non periodic reports (e.g. on context switch) which might
+ * lead to more successful read()s than expected due to
+ * periodic sampling and we don't want these extra reads to
+ * cause the test to fail...
+ */
+ for (int offset = 0; offset < ret; offset += format_size) {
+ uint32_t *report = (void *)(buf + offset);
+
+ if (oa_report_is_periodic(oa_exponent, report))
+ timer_report_read = true;
+ else
+ non_timer_report_read = true;
+ }
+
+ if (non_timer_report_read && !timer_report_read)
+ n_extra_iterations++;
+
+ /* At this point, after consuming pending reports (and hoping
+ * the scheduler hasn't stopped us for too long) we now expect
+ * EAGAIN on read. While this works most of the times, there are
+ * some rare failures when the OA period passed to this test is
+ * very small (say 500 us) and that results in some valid
+ * reports here. To weed out those rare occurences we assert
+ * only if the OA period is >= 40 ms because 40 ms has withstood
+ * the test of time on most platforms (ref: subtest: polling).
+ */
+ while ((ret = read(stream_fd, buf, sizeof(buf))) < 0 &&
+ (errno == EINTR || errno == EIO))
+ ;
+
+ if (requested_oa_period >= 40000000) {
+ igt_assert_eq(ret, -1);
+ igt_assert_eq(errno, EAGAIN);
+ }
+
+ n++;
+ }
+
+ times(&end_times);
+
+ /* Using nanosecond units is fairly silly here, given the tick in-
+ * precision - ah well, it's consistent with the get_time() units.
+ */
+ user_ns = (end_times.tms_utime - start_times.tms_utime) * tick_ns;
+ kernel_ns = (end_times.tms_stime - start_times.tms_stime) * tick_ns;
+
+ igt_debug("%d non-blocking reads during test with %"PRIu64" Hz OA sampling (expect no more than %d)\n",
+ n, NSEC_PER_SEC / oa_period, max_iterations);
+ igt_debug("%d extra iterations seen, not related to periodic sampling (e.g. context switches)\n",
+ n_extra_iterations);
+ igt_debug("time in userspace = %"PRIu64"ns (+-%dns) (start utime = %d, end = %d)\n",
+ user_ns, (int)tick_ns,
+ (int)start_times.tms_utime, (int)end_times.tms_utime);
+ igt_debug("time in kernelspace = %"PRIu64"ns (+-%dns) (start stime = %d, end = %d)\n",
+ kernel_ns, (int)tick_ns,
+ (int)start_times.tms_stime, (int)end_times.tms_stime);
+
+ /* With completely broken blocking while polling (but still somehow
+ * reporting a POLLIN event) we could end up with an open loop.
+ */
+ igt_assert(n <= (max_iterations + n_extra_iterations));
+
+ /* Make sure the driver is reporting new samples with a reasonably
+ * low latency...
+ */
+ igt_assert(n > (min_iterations + n_extra_iterations));
+
+ if (!set_kernel_hrtimer)
+ igt_assert(kernel_ns <= (test_duration_ns / 100ull));
+
+ __perf_close(stream_fd);
+}
+
+/**
+ * SUBTEST: polling-small-buf
+ * Description: Test polled read with buffer size smaller than available data
+ */
+static void test_polling_small_buf(void)
+{
+ int oa_exponent = max_oa_exponent_for_period_lte(40 * 1000); /* 40us */
+ uint64_t properties[] = {
+ DRM_XE_OA_PROPERTY_OA_UNIT_ID, 0,
+
+ /* Include OA reports in samples */
+ DRM_XE_OA_PROPERTY_SAMPLE_OA, true,
+
+ /* OA unit configuration */
+ DRM_XE_OA_PROPERTY_OA_METRIC_SET, default_test_set->perf_oa_metrics_set,
+ DRM_XE_OA_PROPERTY_OA_FORMAT, __ff(default_test_set->perf_oa_format),
+ DRM_XE_OA_PROPERTY_OA_PERIOD_EXPONENT, oa_exponent,
+ DRM_XE_OA_PROPERTY_OA_DISABLED, true,
+ };
+ struct intel_xe_oa_open_prop param = {
+ .num_properties = ARRAY_SIZE(properties) / 2,
+ .properties_ptr = to_user_pointer(properties),
+ };
+ uint32_t test_duration = 80 * 1000 * 1000;
+ int sample_size = get_oa_format(default_test_set->perf_oa_format).size;
+ int n_expected_reports = test_duration / oa_exponent_to_ns(oa_exponent);
+ int n_expect_read_bytes = n_expected_reports * sample_size;
+ struct timespec ts = {};
+ int n_bytes_read = 0;
+ uint32_t n_polls = 0;
+
+ stream_fd = __perf_open(drm_fd, ¶m, true /* prevent_pm */);
+ set_fd_flags(stream_fd, O_CLOEXEC | O_NONBLOCK);
+ do_ioctl(stream_fd, DRM_XE_OBSERVATION_IOCTL_ENABLE, 0);
+
+ while (igt_nsec_elapsed(&ts) < test_duration) {
+ struct pollfd pollfd = { .fd = stream_fd, .events = POLLIN };
+
+ ppoll(&pollfd, 1, NULL, NULL);
+ if (pollfd.revents & POLLIN) {
+ uint8_t buf[1024];
+ int ret;
+
+ ret = read(stream_fd, buf, sizeof(buf));
+ if (ret >= 0)
+ n_bytes_read += ret;
+ }
+
+ n_polls++;
+ }
+
+ igt_info("Read %d expected %d (%.2f%% of the expected number), polls=%u\n",
+ n_bytes_read, n_expect_read_bytes,
+ n_bytes_read * 100.0f / n_expect_read_bytes,
+ n_polls);
+
+ __perf_close(stream_fd);
+
+ igt_assert(abs(n_expect_read_bytes - n_bytes_read) <
+ 0.20 * n_expect_read_bytes);
+}
+
/**
* SUBTEST: buffer-fill
* Description: Test filling, wraparound and overflow of OA buffer
@@ -2463,6 +2907,25 @@ igt_main
__for_one_hwe_in_oag(hwe)
test_enable_disable(hwe);
+ igt_subtest_with_dynamic("blocking") {
+ __for_one_hwe_in_oag(hwe)
+ test_blocking(40 * 1000 * 1000 /* 40ms oa period */,
+ false /* set_kernel_hrtimer */,
+ 5 * 1000 * 1000 /* default 5ms/200Hz hrtimer */,
+ hwe);
+ }
+
+ igt_subtest_with_dynamic("polling") {
+ __for_one_hwe_in_oag(hwe)
+ test_polling(40 * 1000 * 1000 /* 40ms oa period */,
+ false /* set_kernel_hrtimer */,
+ 5 * 1000 * 1000 /* default 5ms/200Hz hrtimer */,
+ hwe);
+ }
+
+ igt_subtest("polling-small-buf")
+ test_polling_small_buf();
+
igt_subtest("short-reads")
test_short_reads();
--
2.41.0
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