benchmarks/gem_syslatency: Specify batch duration

While for stressing the system we want to submit as many batches as we
can as that shows us worst case impact on system latency, it is not a
very realistic case. To introduce a bit more realism allow the batches
run for a user defined duration.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

1 files changed, 67 insertions, 4 deletions

diff --git a/benchmarks/gem_syslatency.c b/benchmarks/gem_syslatency.c
index 6d520bfe..ba5d32a9 100644
--- a/benchmarks/gem_syslatency.c
+++ b/benchmarks/gem_syslatency.c
@@ -51,6 +51,7 @@ static volatile int done;
 
 struct gem_busyspin {
 	pthread_t thread;
+	unsigned long sz;
 	unsigned long count;
 	bool leak;
 	bool interrupts;
@@ -96,7 +97,8 @@ static void *gem_busyspin(void *arg)
 	struct gem_busyspin *bs = arg;
 	struct drm_i915_gem_execbuffer2 execbuf;
 	struct drm_i915_gem_exec_object2 obj[2];
-	const unsigned sz = bs->leak ? 16 << 20 : 4 << 10;
+	const unsigned sz =
+		bs->sz ? bs->sz + sizeof(bbe) : bs->leak ? 16 << 20 : 4 << 10;
 	unsigned engines[16];
 	unsigned nengine;
 	unsigned engine;
@@ -112,7 +114,7 @@ static void *gem_busyspin(void *arg)
 	obj[0].handle = gem_create(fd, 4096);
 	obj[0].flags = EXEC_OBJECT_WRITE;
 	obj[1].handle = gem_create(fd, sz);
-	gem_write(fd, obj[1].handle, 0, &bbe, sizeof(bbe));
+	gem_write(fd, obj[1].handle, bs->sz, &bbe, sizeof(bbe));
 
 	memset(&execbuf, 0, sizeof(execbuf));
 	if (bs->interrupts) {
@@ -131,6 +133,12 @@ static void *gem_busyspin(void *arg)
 
 	while (!done) {
 		for (int n = 0; n < nengine; n++) {
+			const int m = rand() % nengine;
+			unsigned int tmp = engines[n];
+			engines[n] = engines[m];
+			engines[m] = tmp;
+		}
+		for (int n = 0; n < nengine; n++) {
 			execbuf.flags &= ~ENGINE_FLAGS;
 			execbuf.flags |= engines[n];
 			gem_execbuf(fd, &execbuf);
@@ -139,7 +147,7 @@ static void *gem_busyspin(void *arg)
 		if (bs->leak) {
 			gem_madvise(fd, obj[1].handle, I915_MADV_DONTNEED);
 			obj[1].handle = gem_create(fd, sz);
-			gem_write(fd, obj[1].handle, 0, &bbe, sizeof(bbe));
+			gem_write(fd, obj[1].handle, bs->sz, &bbe, sizeof(bbe));
 		}
 	}
 
@@ -299,6 +307,50 @@ static void *background_fs(void *path)
 	return NULL;
 }
 
+static unsigned long calibrate_nop(unsigned int target_us,
+				   unsigned int tolerance_pct)
+{
+	const uint32_t bbe = MI_BATCH_BUFFER_END;
+	const unsigned int loops = 100;
+	struct drm_i915_gem_exec_object2 obj = {};
+	struct drm_i915_gem_execbuffer2 eb =
+		{ .buffer_count = 1, .buffers_ptr = (uintptr_t)&obj};
+	struct timespec t_0, t_end;
+	long sz, prev;
+	int fd;
+
+	fd = drm_open_driver(DRIVER_INTEL);
+
+	clock_gettime(CLOCK_MONOTONIC, &t_0);
+
+	sz = 256 * 1024;
+	do {
+		struct timespec t_start;
+
+		obj.handle = gem_create(fd, sz + sizeof(bbe));
+		gem_write(fd, obj.handle, sz, &bbe, sizeof(bbe));
+		gem_execbuf(fd, &eb);
+		gem_sync(fd, obj.handle);
+
+		clock_gettime(CLOCK_MONOTONIC, &t_start);
+		for (int loop = 0; loop < loops; loop++)
+			gem_execbuf(fd, &eb);
+		gem_sync(fd, obj.handle);
+		clock_gettime(CLOCK_MONOTONIC, &t_end);
+
+		gem_close(fd, obj.handle);
+
+		prev = sz;
+		sz = loops * sz / elapsed(&t_start, &t_end) * 1e3 * target_us;
+		sz = ALIGN(sz, sizeof(uint32_t));
+	} while (elapsed(&t_0, &t_end) < 5 ||
+		 abs(sz - prev) > (sz * tolerance_pct / 100));
+
+	close(fd);
+
+	return sz;
+}
+
 int main(int argc, char **argv)
 {
 	struct gem_busyspin *busy;
@@ -314,9 +366,10 @@ int main(int argc, char **argv)
 	int enable_gem_sysbusy = 1;
 	bool leak = false;
 	bool interrupts = false;
+	long batch = 0;
 	int n, c;
 
-	while ((c = getopt(argc, argv, "t:f:bmni1")) != -1) {
+	while ((c = getopt(argc, argv, "r:t:f:bmni1")) != -1) {
 		switch (c) {
 		case '1':
 			ncpus = 1;
@@ -333,6 +386,10 @@ int main(int argc, char **argv)
 			if (time < 0)
 				time = INT_MAX;
 			break;
+		case 'r':
+			/* Duration of each batch (microseconds) */
+			batch = atoi(optarg);
+			break;
 		case 'f':
 			/* Select an output field */
 			field = atoi(optarg);
@@ -355,11 +412,17 @@ int main(int argc, char **argv)
 	force_low_latency();
 	min = min_measurement_error();
 
+	if (batch > 0)
+		batch = calibrate_nop(batch, 2);
+	else
+		batch = -batch;
+
 	busy = calloc(ncpus, sizeof(*busy));
 	pthread_attr_init(&attr);
 	if (enable_gem_sysbusy) {
 		for (n = 0; n < ncpus; n++) {
 			bind_cpu(&attr, n);
+			busy[n].sz = batch;
 			busy[n].leak = leak;
 			busy[n].interrupts = interrupts;
 			pthread_create(&busy[n].thread, &attr,