[RFC PATCH 1/1] drm/mm: add ig_frag selftest

[Nirmoy Das]

This patch introduces fragmentation in the address range
and measures time taken by 10k and 20k insertions. ig_frag()
will fail if time taken by 20k insertions takes more than 4 times
of 10k insertions as we know that insertions scale quadratically.
Also tolerate 10% error because of kernel scheduler's jitters.

Output:
<snip>
[ 8092.653518] drm_mm: Testing DRM range manger (struct drm_mm), with random_seed=0x9bfb4117 max_iterations=8192 max_prime=128
[ 8092.653520] drm_mm: igt_sanitycheck - ok!
[ 8092.653525] igt_debug 0x0000000000000000-0x0000000000000200: 512: free
[ 8092.653526] igt_debug 0x0000000000000200-0x0000000000000600: 1024: used
[ 8092.653527] igt_debug 0x0000000000000600-0x0000000000000a00: 1024: free
[ 8092.653528] igt_debug 0x0000000000000a00-0x0000000000000e00: 1024: used
[ 8092.653529] igt_debug 0x0000000000000e00-0x0000000000001000: 512: free
[ 8092.653529] igt_debug total: 4096, used 2048 free 2048
[ 8112.569813] drm_mm: best fragmented insert of 10000 and 20000 insertions took 504 and 1996 msecs
[ 8112.723254] drm_mm: bottom-up fragmented insert of 10000 and 20000 insertions took 44 and 108 msecs
[ 8112.813212] drm_mm: top-down fragmented insert of 10000 and 20000 insertions took 40 and 44 msecs
[ 8112.847733] drm_mm: evict fragmented insert of 10000 and 20000 insertions took 8 and 20 msecs
<snip>

Signed-off-by: Nirmoy Das <nirmoy.das at amd.com>
---
 drivers/gpu/drm/selftests/drm_mm_selftests.h |  1 +
 drivers/gpu/drm/selftests/test-drm_mm.c      | 73 ++++++++++++++++++++
 2 files changed, 74 insertions(+)

diff --git a/drivers/gpu/drm/selftests/drm_mm_selftests.h b/drivers/gpu/drm/selftests/drm_mm_selftests.h
index 6b943ea1c57d..8c87c964176b 100644
--- a/drivers/gpu/drm/selftests/drm_mm_selftests.h
+++ b/drivers/gpu/drm/selftests/drm_mm_selftests.h
@@ -14,6 +14,7 @@ selftest(insert, igt_insert)
 selftest(replace, igt_replace)
 selftest(insert_range, igt_insert_range)
 selftest(align, igt_align)
+selftest(frag, igt_frag)
 selftest(align32, igt_align32)
 selftest(align64, igt_align64)
 selftest(evict, igt_evict)
diff --git a/drivers/gpu/drm/selftests/test-drm_mm.c b/drivers/gpu/drm/selftests/test-drm_mm.c
index 9aabe82dcd3a..05d8f3659b4d 100644
--- a/drivers/gpu/drm/selftests/test-drm_mm.c
+++ b/drivers/gpu/drm/selftests/test-drm_mm.c
@@ -1033,6 +1033,79 @@ static int igt_insert_range(void *ignored)
 	return 0;
 }
 
+static int get_insert_time(unsigned int num_insert,
+			   const struct insert_mode *mode)
+{
+	struct drm_mm mm;
+	struct drm_mm_node *nodes, *node, *next;
+	unsigned int size = 4096, align = 8192;
+	unsigned long start;
+	unsigned int i;
+	int ret = -EINVAL;
+
+	drm_mm_init(&mm, 1, U64_MAX - 2);
+	nodes = vzalloc(array_size(num_insert, sizeof(*nodes)));
+	if (!nodes)
+		goto err;
+
+	start = jiffies;
+	for (i = 0; i < num_insert; i++) {
+		if (!expect_insert(&mm, &nodes[i], size, align, i, mode)) {
+			pr_err("%s insert failed\n", mode->name);
+			goto out;
+		}
+	}
+
+	ret = jiffies_to_msecs(jiffies - start);
+out:
+	drm_mm_for_each_node_safe(node, next, &mm)
+		drm_mm_remove_node(node);
+	drm_mm_takedown(&mm);
+	vfree(nodes);
+err:
+	return ret;
+
+}
+
+static int igt_frag(void *ignored)
+{
+	const struct insert_mode *mode;
+	unsigned int insert_time1, insert_time2;
+	unsigned int insert_size = 10000;
+	unsigned int scale_factor = 4;
+	/* tolerate 10% excess insertion duration */
+	unsigned int error_factor = 110;
+	int ret = -EINVAL;
+
+	for (mode = insert_modes; mode->name; mode++) {
+		unsigned int expected_time;
+
+		insert_time1 = get_insert_time(insert_size, mode);
+		if (insert_time1 < 0)
+			goto err;
+
+		insert_time2 = get_insert_time((insert_size * 2), mode);
+		if (insert_time2 < 0)
+			goto err;
+
+		expected_time = (scale_factor * insert_time1 *
+				 error_factor)/100;
+		if (insert_time2 > expected_time) {
+			pr_err("%s fragmented insert took more %u msecs\n",
+			       mode->name, insert_time2 - expected_time);
+			goto err;
+		}
+
+		pr_info("%s fragmented insert of %u and %u insertions took %u and %u msecs\n",
+			mode->name, insert_size, insert_size * 2, insert_time1,
+			insert_time2);
+	}
+
+	ret = 0;
+err:
+	return ret;
+}
+
 static int igt_align(void *ignored)
 {
 	const struct insert_mode *mode;
-- 
2.26.2