benchmarks: Measure round-trip time for an immediate vblanks

By measuring both the query and the event round trip time, we can make a
reasonable estimate of how long it takes for the query to send the
vblank following an interrupt.

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

benchmarks/Makefile.sources

@@ -6,4 +6,6 @@ bin_PROGRAMS =                          \
 	gem_exec_nop			\
 	gem_mmap			\
 	gem_prw				\
-	gem_userptr_benchmark
+	gem_userptr_benchmark		\
+	kms_vblank			\
+	$(NULL)

benchmarks/kms_vblank.c

@@ -0,0 +1,180 @@
+/*
+ * Copyright © 2015 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.
+ */
+
+/** @file kms_vblank.c
+ *
+ * This is a test of performance of drmWaitVblank.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/wait.h>
+
+#include <drm.h>
+#include <xf86drm.h>
+#include "drmtest.h"
+
+static double elapsed(const struct timespec *start,
+		      const struct timespec *end,
+		      int loop)
+{
+	return (1e6*(end->tv_sec - start->tv_sec) + (end->tv_nsec - start->tv_nsec)/1000)/loop;
+}
+
+static int crtc0_active(int fd)
+{
+	union drm_wait_vblank vbl;
+
+	memset(&vbl, 0, sizeof(vbl));
+	vbl.request.type = DRM_VBLANK_RELATIVE;
+	return drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, &vbl) == 0;
+}
+
+static void vblank_query(int fd, int busy)
+{
+	union drm_wait_vblank vbl;
+	struct timespec start, end;
+	unsigned long seq, count = 0;
+	struct drm_event_vblank event;
+
+	memset(&vbl, 0, sizeof(vbl));
+
+	if (busy) {
+		vbl.request.type = DRM_VBLANK_RELATIVE | DRM_VBLANK_EVENT;
+		vbl.request.sequence = 120 + 12;
+		drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, &vbl);
+	}
+
+	vbl.request.type = DRM_VBLANK_RELATIVE;
+	vbl.request.sequence = 0;
+	drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, &vbl);
+	seq = vbl.reply.sequence;
+
+	clock_gettime(CLOCK_MONOTONIC, &start);
+	do {
+		vbl.request.type = DRM_VBLANK_RELATIVE;
+		vbl.request.sequence = 0;
+		drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, &vbl);
+		count++;
+	} while ((vbl.reply.sequence - seq) <= 120);
+	clock_gettime(CLOCK_MONOTONIC, &end);
+
+	printf("%f\n", 1e6/elapsed(&start, &end, count));
+	if (busy)
+		read(fd, &event, sizeof(event));
+}
+
+static void vblank_event(int fd, int busy)
+{
+	union drm_wait_vblank vbl;
+	struct timespec start, end;
+	unsigned long seq, count = 0;
+	struct drm_event_vblank event;
+
+	memset(&vbl, 0, sizeof(vbl));
+
+	if (busy) {
+		vbl.request.type = DRM_VBLANK_RELATIVE | DRM_VBLANK_EVENT;
+		vbl.request.sequence = 120 + 12;
+		drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, &vbl);
+	}
+
+	vbl.request.type = DRM_VBLANK_RELATIVE;
+	vbl.request.sequence = 0;
+	drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, &vbl);
+	seq = vbl.reply.sequence;
+
+	clock_gettime(CLOCK_MONOTONIC, &start);
+	do {
+		vbl.request.type = DRM_VBLANK_RELATIVE | DRM_VBLANK_EVENT;
+		vbl.request.sequence = 0;
+		drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, &vbl);
+
+		read(fd, &event, sizeof(event));
+		count++;
+	} while ((event.sequence - seq) <= 120);
+	clock_gettime(CLOCK_MONOTONIC, &end);
+
+	printf("%f\n", 1e6/elapsed(&start, &end, count));
+	if (busy)
+		read(fd, &event, sizeof(event));
+}
+
+int main(int argc, char **argv)
+{
+	int fd, c;
+	int busy = 0, loops = 5;
+	enum what { EVENTS, QUERIES } what = EVENTS;
+
+	while ((c = getopt (argc, argv, "b:w:r:")) != -1) {
+		switch (c) {
+		case 'b':
+			if (strcmp(optarg, "busy") == 0)
+				busy = 1;
+			else if (strcmp(optarg, "idle") == 0)
+				busy = 0;
+			else
+				abort();
+			break;
+
+		case 'w':
+			if (strcmp(optarg, "event") == 0)
+				what = EVENTS;
+			else if (strcmp(optarg, "query") == 0)
+				what = QUERIES;
+			else
+				abort();
+			break;
+		case 'r':
+			loops = atoi(optarg);
+			if (loops < 1)
+				loops = 1;
+		}
+	}
+
+	fd = drm_open_any();
+	if (!crtc0_active(fd)) {
+		fprintf(stderr, "CRTC/pipe 0 not active\n");
+		return 77;
+	}
+
+	while (loops--) {
+		switch (what) {
+		case EVENTS:
+			vblank_event(fd, busy);
+			break;
+		case QUERIES:
+			vblank_query(fd, busy);
+			break;
+		}
+	}
+	return 0;
+}