Re: [PATCH i-g-t CI run 06/14] tests/intel/xe_oa: Rewrite the polling small buf test

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Mon, 24 Feb 2025 16:02:05 -0800, Umesh Nerlige Ramappa wrote:
> 


Hi Umesh,

You seem to have responded twice on the CI series. I have responded on this
on the original series. Let's keep to the original series if possible. I am
monitoring the R-b's etc. there.

Thanks.
--
Ashutosh


> On Mon, Feb 24, 2025 at 02:56:05PM -0800, Umesh Nerlige Ramappa wrote:
> > On Mon, Feb 24, 2025 at 12:11:37PM -0800, Dixit, Ashutosh wrote:
> >> On Tue, 18 Feb 2025 12:28:04 -0800, Umesh Nerlige Ramappa wrote:
> >>> 
> >> 
> >> Hi Umesh,
> >> 
> >>> Use mmio reads as a side-channel to determine if reports are available
> >>> and ensure that poll will return with POLLIN set. Then provide a small
> >>> buffer to force ENOSPC error. Then poll with a timeout of 0 to check if
> >>> POLLIN is still set.
> >> 
> >> Will need a reason for doing this here. But see below.
> >> 
> >>> 
> >>> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> >>> ---
> >>> tests/intel/xe_oa.c | 64 +++++++++++++++++++++++++--------------------
> >>> 1 file changed, 35 insertions(+), 29 deletions(-)
> >>> 
> >>> diff --git a/tests/intel/xe_oa.c b/tests/intel/xe_oa.c
> >>> index aaf92308a..5792ffec2 100644
> >>> --- a/tests/intel/xe_oa.c
> >>> +++ b/tests/intel/xe_oa.c
> >>> @@ -2216,7 +2216,6 @@ static void test_polling(uint64_t requested_oa_period,
> >>>  */
> >>> 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,
> >>> 
> >>> @@ -2226,50 +2225,57 @@ static void test_polling_small_buf(void)
> >>> 		/* 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_PERIOD_EXPONENT, oa_exponent_default,
> >>> 		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;
> >>> +	int report_size = get_oa_format(default_test_set->perf_oa_format).size;
> >>> +	u32 oa_tail, prev_tail;
> >>> +	struct pollfd pollfd;
> >>> +	uint8_t buf[10];
> >>> +	int ret, i = 0;
> >>> +
> >>> +	intel_register_access_init(&mmio_data,
> >>> +				   igt_device_get_pci_device(drm_fd), 0);
> >>> 
> >>> 	stream_fd = __perf_open(drm_fd, &param, 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;
> >>> +#define OAG_OATAILPTR	(0xdb04)
> >>> +	/* Save the current tail */
> >>> +	prev_tail = oa_tail = intel_register_read(&mmio_data, OAG_OATAILPTR);
> >>> 
> >>> -			ret = read(stream_fd, buf, sizeof(buf));
> >>> -			if (ret >= 0)
> >>> -				n_bytes_read += ret;
> >>> -		}
> >>> +	/* Kickstart the capture */
> >>> +	do_ioctl(stream_fd, DRM_XE_OBSERVATION_IOCTL_ENABLE, 0);
> >>> 
> >>> -		n_polls++;
> >>> +	/* Wait for 5 reports */
> >> 
> >> Wait for 5 reports or 10 ms ?
> >> 
> >> 
> >>> +	while ((oa_tail - prev_tail) < (5 * report_size)) {
> >>> +		usleep(1000);
> >>> +		oa_tail = intel_register_read(&mmio_data, OAG_OATAILPTR);
> >>> +		if (i++ > 10)
> >> 
> >> So on slow platforms we might not get any reports in 10 ms? The idea here
> >> should be to not have any timing dependence? So if we want to wait for 5
> >> reports, just wait for 5 reports?
> 
> Oh, I think the loop was stuck while debugging something, so had added a
> counter to bail out in 10 iterations. I will remove that. We only need to
> wait for 5 reports.
> 
> >> 
> >> We tried doing this for the mmap OA buffer: see
> >> mmap_wait_for_periodic_reports(), the function waits indefinitely.
> 
> You mean this:
> 
> while (num_periodic_reports < n) {
> 	usleep(4 * n * period_us);
> 	num_periodic_reports = 0;
> 	for (reports = (uint32_t *)oa_vaddr;
> 	     reports[0] && oa_timestamp(reports, fmt) && oa_report_is_periodic(reports);
> 	     reports += get_oa_format(fmt).size) {
> 		num_periodic_reports++;
> 	}
> }
> 
> Well.. if your reports start coming in fast enough, then you would just
> spin in the inner for loop. Maybe break the inner for loop when
> num_periodic_reports >= n;
> 
> >> 
> >> So if this is done I am not sure if the intel_register_read() approach is
> >> needed (but I didn't think of doing that :). But I guess we can use it to
> >> see when there are N reports available.
> >> 
> >> Longer term it would be nice to have a centralized function
> >> wait_for_n_reports(int n) or something like that which different tests can
> >> use.
> 
> Agree, except that some tests will read the actual reports, while others
> ust want to take a peek at how many reports are available without reading
> them. Since mmap is also a feature under test, I took the easier
> approach. We can always refine it if we find something better.
> > 
> >> 
> >>> +			break;
> >>> 	}
> >>> 
> >>> -	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);
> >>> +	intel_register_access_fini(&mmio_data);
> >>> 
> >>> -	__perf_close(stream_fd);
> >>> +	/* Just read one report and expect ENOSPC */
> >>> +	pollfd.fd = stream_fd;
> >>> +	pollfd.events = POLLIN;
> >>> +	poll(&pollfd, 1, 1000);
> >>> +	igt_assert(pollfd.revents & POLLIN);
> >> 
> >> Is the assumption here that the kernel timer is firing every 5 ms (so if
> >> we've waited for 10 ms POLLIN must be set since the timer is firing every 5
> >> ms)? I am not sure if that 5 ms is uapi. Or is it? Actually I was thinking
> 
> But here I am waiting 1000ms in the poll above. That should be sufficient
> for POLLIN  to be set. If not, we could set the timeout to a large value (a
> few seconds).
> 
> >> 
> >>> +	errno = 0;
> >>> +	ret = read(stream_fd, buf, sizeof(buf));
> >>> +	igt_assert_eq(ret, -1);
> >>> +	igt_assert_eq(errno, ENOSPC);
> >> 
> >> This part looks ok, it's uapi.
> >> 
> 
> Note:
> ENOSPC is returned only if the buffer is small enough that not even one
> report will fit in. Initially I had a 600 byte buffer, but I did not get
> ENOSPC. Instead I got 576 in ret which I think is the correct behavior.
> 
> >>> 
> >>> -	igt_assert(abs(n_expect_read_bytes - n_bytes_read) <
> >>> -		   0.20 * n_expect_read_bytes);
> >>> +	/* Poll with 0 timeout and expect POLLIN flag to be set */
> >>> +	poll(&pollfd, 1, 0);
> >>> +	igt_assert(pollfd.revents & POLLIN);
> >>> +
> >>> +	__perf_close(stream_fd);
> >> 
> >> How about just reading N reports using a small buffer for this test,
> >> however long it takes? N can 5 or 10.
> 
> Not sure I understand. You mean at this stage of the test, read 5/10
> reports? OR just alter the entire test somehow to do something different?
> 
> I thought the test was specifically testing that POLLIN is still set after
> an ENOSPC error, so I have written it for that case alone. The 0 timeout
> will bypass the wait in the poll so that we only get the state of POLLIN.
> 
> Thanks,
> Umesh
> 
> 
> >> 
> >> Thanks.
> >> --
> >> Ashutosh
> >> 
> >> PS: how about separating out the patches which currently have R-b into a
> >> separate series and merging them first?