benchmarks: Add gem_syslatency

Instead of measuring the wakeup latency of a GEM client, we turn the
tables here and ask what is the wakeup latency of a normal process
competing with GEM. In particular, a realtime process that expects
deterministic latency.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

benchmarks/Makefile.am

@@ -11,5 +11,7 @@ gem_exec_tracer_la_LIBADD = -ldl
 
 gem_latency_CFLAGS = $(AM_CFLAGS) $(THREAD_CFLAGS)
 gem_latency_LDADD = $(LDADD) -lpthread
+gem_syslatency_CFLAGS = $(AM_CFLAGS) $(THREAD_CFLAGS)
+gem_syslatency_LDADD = $(LDADD) -lpthread -lrt
 
 EXTRA_DIST=README

benchmarks/Makefile.sources

@@ -15,6 +15,7 @@ benchmarks_PROGRAMS =			\
 	gem_mmap			\
 	gem_prw				\
 	gem_set_domain			\
+	gem_syslatency			\
 	gem_userptr_benchmark		\
 	kms_vblank			\
 	$(NULL)

benchmarks/gem_syslatency.c

@@ -0,0 +1,301 @@
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#define _GNU_SOURCE
+
+#include "igt.h"
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <pthread.h>
+#include <sched.h>
+#include <signal.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+#include <time.h>
+#include <limits.h>
+#include "drm.h"
+
+#include <linux/unistd.h>
+
+#define gettid() syscall(__NR_gettid)
+#define sigev_notify_thread_id _sigev_un._tid
+
+static volatile int done;
+
+struct gem_busyspin {
+	pthread_t thread;
+	int cpu;
+	unsigned long count;
+};
+
+struct sys_wait {
+	pthread_t thread;
+	int cpu;
+	struct igt_mean mean;
+};
+
+static void bind_cpu(pthread_t thread, int cpu)
+{
+	cpu_set_t mask;
+
+	if (cpu == -1)
+		return;
+
+	CPU_ZERO(&mask);
+	CPU_SET(cpu, &mask);
+
+	pthread_setaffinity_np(thread, sizeof(mask), &mask);
+}
+
+#define LOCAL_I915_EXEC_NO_RELOC (1<<11)
+#define LOCAL_I915_EXEC_HANDLE_LUT (1<<12)
+
+#define LOCAL_I915_EXEC_BSD_SHIFT      (13)
+#define LOCAL_I915_EXEC_BSD_MASK       (3 << LOCAL_I915_EXEC_BSD_SHIFT)
+
+#define ENGINE_FLAGS  (I915_EXEC_RING_MASK | LOCAL_I915_EXEC_BSD_MASK)
+
+static bool ignore_engine(int fd, unsigned engine)
+{
+	if (engine == 0)
+		return true;
+
+	if (gem_has_bsd2(fd) && engine == I915_EXEC_BSD)
+		return true;
+
+	return false;
+}
+
+static void *gem_busyspin(void *arg)
+{
+	const uint32_t bbe = MI_BATCH_BUFFER_END;
+	struct gem_busyspin *bs = arg;
+	struct drm_i915_gem_execbuffer2 execbuf;
+	struct drm_i915_gem_exec_object2 obj;
+	unsigned engines[16];
+	unsigned nengine;
+	unsigned engine;
+	int fd;
+
+	bind_cpu(bs->thread, bs->cpu);
+
+	fd = drm_open_driver(DRIVER_INTEL);
+
+	nengine = 0;
+	for_each_engine(fd, engine)
+		if (!ignore_engine(fd, engine)) engines[nengine++] = engine;
+	igt_require(nengine);
+
+	memset(&obj, 0, sizeof(obj));
+	obj.handle = gem_create(fd, 4096);
+	gem_write(fd, obj.handle, 0, &bbe, sizeof(bbe));
+
+	memset(&execbuf, 0, sizeof(execbuf));
+	execbuf.buffers_ptr = (uintptr_t)&obj;
+	execbuf.buffer_count = 1;
+	execbuf.flags |= LOCAL_I915_EXEC_HANDLE_LUT;
+	execbuf.flags |= LOCAL_I915_EXEC_NO_RELOC;
+	if (__gem_execbuf(fd, &execbuf) == 0) {
+		execbuf.flags = 0;
+		gem_execbuf(fd, &execbuf);
+	}
+
+	while (!done) {
+		for (int n = 0; n < nengine; n++) {
+			execbuf.flags &= ~ENGINE_FLAGS;
+			execbuf.flags |= engines[n];
+			gem_execbuf(fd, &execbuf);
+		}
+		bs->count += nengine;
+	}
+
+	close(fd);
+	return NULL;
+}
+
+#define MSEC_PER_SEC (1000)
+#define USEC_PER_SEC (1000 * MSEC_PER_SEC)
+#define NSEC_PER_SEC (1000 * USEC_PER_SEC)
+
+static double elapsed(const struct timespec *a, const struct timespec *b)
+{
+	return NSEC_PER_SEC*(b->tv_sec - a->tv_sec) + (b->tv_nsec - a ->tv_nsec);
+}
+
+static void *sys_wait(void *arg)
+{
+	struct sys_wait *w = arg;
+	struct sigevent sev;
+	timer_t timer;
+	sigset_t mask;
+	struct timespec now;
+#define SIG SIGRTMIN
+
+	bind_cpu(w->thread, w->cpu);
+
+	sigemptyset(&mask);
+	sigaddset(&mask, SIG);
+	sigprocmask(SIG_SETMASK, &mask, NULL);
+
+	sev.sigev_notify = SIGEV_SIGNAL | SIGEV_THREAD_ID;
+	sev.sigev_notify_thread_id = gettid();
+	sev.sigev_signo = SIG;
+	timer_create(CLOCK_MONOTONIC, &sev, &timer);
+
+	clock_gettime(CLOCK_MONOTONIC, &now);
+	while (!done) {
+		struct itimerspec its;
+		int sigs;
+
+		its.it_value = now;
+		its.it_value.tv_nsec += 100 * 1000;
+		its.it_value.tv_nsec += rand() % (NSEC_PER_SEC / 1000);
+		if (its.it_value.tv_nsec >= NSEC_PER_SEC) {
+			its.it_value.tv_nsec -= NSEC_PER_SEC;
+			its.it_value.tv_sec += 1;
+		}
+		its.it_interval.tv_sec = its.it_interval.tv_nsec = 0;
+		timer_settime(timer, TIMER_ABSTIME, &its, NULL);
+
+		sigwait(&mask, &sigs);
+		clock_gettime(CLOCK_MONOTONIC, &now);
+		igt_mean_add(&w->mean, elapsed(&its.it_value, &now));
+	}
+
+	sigprocmask(SIG_UNBLOCK, &mask, NULL);
+	timer_delete(timer);
+
+	return NULL;
+}
+
+static void rtprio(pthread_attr_t *attr, int prio)
+{
+#ifdef PTHREAD_EXPLICIT_SCHED
+	struct sched_param param = { .sched_priority = 99 };
+	pthread_attr_setinheritsched(attr, PTHREAD_EXPLICIT_SCHED);
+	pthread_attr_setschedpolicy(attr, SCHED_FIFO);
+	pthread_attr_setschedparam(attr, &param);
+#endif
+}
+
+static double l_estimate(igt_stats_t *stats)
+{
+	if (stats->n_values > 9)
+		return igt_stats_get_trimean(stats);
+	else if (stats->n_values > 5)
+		return igt_stats_get_median(stats);
+	else
+		return igt_stats_get_mean(stats);
+}
+
+int main(int argc, char **argv)
+{
+	struct gem_busyspin *busy;
+	struct sys_wait *wait;
+	pthread_attr_t attr;
+	int ncpus = sysconf(_SC_NPROCESSORS_ONLN);
+	igt_stats_t cycles, mean, max;
+	int time = 10;
+	int field = -1;
+	int n, c;
+
+	while ((c = getopt(argc, argv, "t:f:")) != -1) {
+		switch (c) {
+		case 't':
+			/* How long to run the benchmark for (seconds) */
+			time = atoi(optarg);
+			if (time < 0)
+				time = INT_MAX;
+			break;
+		case 'f':
+			/* Select an output field */
+			field = atoi(optarg);
+			break;
+		default:
+			break;
+		}
+
+	}
+
+	busy = calloc(ncpus, sizeof(*busy));
+	wait = calloc(ncpus, sizeof(*wait));
+
+	for (n = 0; n < ncpus; n++) {
+		busy[n].cpu = n;
+		pthread_create(&busy[n].thread, NULL, gem_busyspin, &busy[n]);
+	}
+
+	pthread_attr_init(&attr);
+	rtprio(&attr, 99);
+	for (n = 0; n < ncpus; n++) {
+		wait[n].cpu = n;
+		igt_mean_init(&wait[n].mean);
+		pthread_create(&wait[n].thread, &attr, sys_wait, &wait[n]);
+	}
+
+	sleep(time);
+	done = 1;
+
+	igt_stats_init_with_size(&cycles, ncpus);
+	for (n = 0; n < ncpus; n++) {
+		pthread_join(busy[n].thread, NULL);
+		igt_stats_push(&cycles, busy[n].count);
+	}
+
+	igt_stats_init_with_size(&mean, ncpus);
+	igt_stats_init_with_size(&max, ncpus);
+	for (n = 0; n < ncpus; n++) {
+		pthread_join(wait[n].thread, NULL);
+		igt_stats_push_float(&mean, wait[n].mean.mean);
+		igt_stats_push_float(&max, wait[n].mean.max);
+	}
+
+	switch (field) {
+	default:
+		printf("gem_syslatency: cycles=%.0f, latency mean=%.3fns max=%.0fns\n",
+		       igt_stats_get_mean(&cycles),
+		       igt_stats_get_mean(&mean),
+		       l_estimate(&max));
+		break;
+	case 0:
+		printf("%.0f\n", igt_stats_get_mean(&cycles));
+		break;
+	case 1:
+		printf("%.3f\n", igt_stats_get_mean(&mean));
+		break;
+	case 2:
+		printf("%.0f\n", l_estimate(&max));
+		break;
+	}
+
+	return 0;
+
+}

lib/igt_stats.h

@@ -27,6 +27,7 @@
 
 #include <stdint.h>
 #include <stdbool.h>
+#include <math.h>
 
 /**
  * igt_stats_t:
@@ -81,20 +82,26 @@ double igt_stats_get_variance(igt_stats_t *stats);
 double igt_stats_get_std_deviation(igt_stats_t *stats);
 
 struct igt_mean {
-	double mean, sq;
+	double mean, sq, min, max;
 	unsigned long count;
 };
 
 static inline void igt_mean_init(struct igt_mean *m)
 {
 	memset(m, 0, sizeof(*m));
+	m->max = -HUGE_VAL;
+	m->min = HUGE_VAL;
 }
 
 static inline void igt_mean_add(struct igt_mean *m, double v)
 {
 	double delta = v - m->mean;
-	m->mean += delta / m->count++;
+	m->mean += delta / ++m->count;
 	m->sq += delta * (v - m->mean);
+	if (v < m->min)
+		m->min = v;
+	if (v > m->max)
+		m->max = v;
 }
 
 static inline double igt_mean_get(struct igt_mean *m)