Re: [Intel-gfx] [PATCH i-g-t] intel_gpu_top: Use actual period when calculating client busyness

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

lgtm,

Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>

On Tue, Mar 14, 2023 at 12:17:40PM +0000, Tvrtko Ursulin wrote:
>From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>
>On a slow machine, or with many processes and/or file descriptors to
>parse, the period of the scanning loop can drift significantly from the
>assumed value. This results in artificially inflated client busyness
>percentages.
>
>To alleviate the issue take some real timestamps and use actual elapsed
>time when calculating relative busyness.
>
>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>---
> tools/intel_gpu_top.c | 39 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 38 insertions(+), 1 deletion(-)
>
>diff --git a/tools/intel_gpu_top.c b/tools/intel_gpu_top.c
>index e13e35b71f4b..af4b350da8e4 100644
>--- a/tools/intel_gpu_top.c
>+++ b/tools/intel_gpu_top.c
>@@ -43,6 +43,7 @@
> #include <sys/types.h>
> #include <unistd.h>
> #include <termios.h>
>+#include <time.h>
> #include <sys/sysmacros.h>
>
> #include "igt_perf.h"
>@@ -2524,6 +2525,38 @@ static void show_help_screen(void)
> "\n");
> }
>
>+static int gettime(struct timespec *ts)
>+{
>+	memset(ts, 0, sizeof(*ts));
>+
>+#ifdef CLOCK_MONOTONIC_RAW
>+	if (!clock_gettime(CLOCK_MONOTONIC_RAW, ts))
>+		return 0;
>+#endif
>+#ifdef CLOCK_MONOTONIC_COARSE
>+	if (!clock_gettime(CLOCK_MONOTONIC_COARSE, ts))
>+		return 0;
>+#endif
>+
>+	return clock_gettime(CLOCK_MONOTONIC, ts);
>+}
>+
>+static unsigned long elapsed_us(struct timespec *prev, unsigned int period_us)
>+{
>+	unsigned long elapsed;
>+	struct timespec now;
>+
>+	if (gettime(&now))
>+		return period_us;
>+
>+	elapsed = ((now.tv_nsec - prev->tv_nsec) / 1000 +
>+	           (unsigned long)USEC_PER_SEC * (now.tv_sec - prev->tv_sec));
>+
>+	*prev = now;
>+
>+	return elapsed;
>+}
>+
> int main(int argc, char **argv)
> {
> 	unsigned int period_us = DEFAULT_PERIOD_MS * 1000;
>@@ -2537,6 +2570,7 @@ int main(int argc, char **argv)
> 	char *pmu_device, *opt_device = NULL;
> 	struct igt_device_card card;
> 	char *codename = NULL;
>+	struct timespec ts;
>
> 	/* Parse options */
> 	while ((ch = getopt(argc, argv, "o:s:d:pcJLlh")) != -1) {
>@@ -2690,6 +2724,7 @@ int main(int argc, char **argv)
>
> 	pmu_sample(engines);
> 	scan_clients(clients, false);
>+	gettime(&ts);
> 	codename = igt_device_get_pretty_name(&card, false);
>
> 	if (output_mode == JSON)
>@@ -2698,6 +2733,7 @@ int main(int argc, char **argv)
> 	while (!stop_top) {
> 		struct clients *disp_clients;
> 		bool consumed = false;
>+		unsigned int scan_us;
> 		int j, lines = 0;
> 		struct winsize ws;
> 		struct client *c;
>@@ -2720,6 +2756,7 @@ int main(int argc, char **argv)
> 		t = (double)(engines->ts.cur - engines->ts.prev) / 1e9;
>
> 		disp_clients = scan_clients(clients, true);
>+		scan_us = elapsed_us(&ts, period_us);
>
> 		if (stop_top)
> 			break;
>@@ -2757,7 +2794,7 @@ int main(int argc, char **argv)
>
> 					lines = print_client(c, engines, t,
> 							     lines, con_w,
>-							     con_h, period_us,
>+							     con_h, scan_us,
> 							     &class_w);
> 				}
>
>-- 
>2.37.2
>