drm/i915: Squash repeated awaits on the same fence

Track the latest fence waited upon on each context, and only add a new
asynchronous wait if the new fence is more recent than the recorded
fence for that context. This requires us to filter out unordered
timelines, which are noted by DMA_FENCE_NO_CONTEXT. However, in the
absence of a universal identifier, we have to use our own
i915->mm.unordered_timeline token.

v2: Throw around the debug crutches
v3: Inline the likely case of the pre-allocation cache being full.
v4: Drop the pre-allocation support, we can lose the most recent fence
in case of allocation failure -- it just means we may emit more awaits
than strictly necessary but will not break.
v5: Trim allocation size for leaf nodes, they only need an array of u32
not pointers.
v6: Create mock_timeline to tidy selftest writing
v7: s/intel_timeline_sync_get/intel_timeline_sync_is_later/ (Tvrtko)
v8: Prune the stale sync points when we idle.
v9: Include a small benchmark in the kselftests
v10: Separate the idr implementation into its own compartment. (Tvrkto)
v11: Refactor igt_sync kselftests to avoid deep nesting (Tvrkto)
v12: __sync_leaf_idx() to assert that p->height is 0 when checking leaves
v13: kselftests to investigate struct i915_syncmap itself (Tvrtko)
v14: Foray into ascii art graphs
v15: Take into account that the random lookup/insert does 2 prng calls,
not 1, when benchmarking, and use for_each_set_bit() (Tvrtko)
v16: Improved ascii art

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170503093924.5320-4-chris@chris-wilson.co.uk

1 files changed, 616 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/selftests/i915_syncmap.c b/drivers/gpu/drm/i915/selftests/i915_syncmap.c
new file mode 100644
index 000000000000..bcab3d00a785
--- /dev/null
+++ b/drivers/gpu/drm/i915/selftests/i915_syncmap.c
@@ -0,0 +1,616 @@
+/*
+ * Copyright © 2017 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.
+ *
+ */
+
+#include "../i915_selftest.h"
+#include "i915_random.h"
+
+static char *
+__sync_print(struct i915_syncmap *p,
+	     char *buf, unsigned long *sz,
+	     unsigned int depth,
+	     unsigned int last,
+	     unsigned int idx)
+{
+	unsigned long len;
+	unsigned int i, X;
+
+	if (depth) {
+		unsigned int d;
+
+		for (d = 0; d < depth - 1; d++) {
+			if (last & BIT(depth - d - 1))
+				len = scnprintf(buf, *sz, "|   ");
+			else
+				len = scnprintf(buf, *sz, "    ");
+			buf += len;
+			*sz -= len;
+		}
+		len = scnprintf(buf, *sz, "%x-> ", idx);
+		buf += len;
+		*sz -= len;
+	}
+
+	/* We mark bits after the prefix as "X" */
+	len = scnprintf(buf, *sz, "0x%016llx", p->prefix << p->height << SHIFT);
+	buf += len;
+	*sz -= len;
+	X = (p->height + SHIFT) / 4;
+	scnprintf(buf - X, *sz + X, "%*s", X, "XXXXXXXXXXXXXXXXX");
+
+	if (!p->height) {
+		for_each_set_bit(i, (unsigned long *)&p->bitmap, KSYNCMAP) {
+			len = scnprintf(buf, *sz, " %x:%x,",
+					i, __sync_seqno(p)[i]);
+			buf += len;
+			*sz -= len;
+		}
+		buf -= 1;
+		*sz += 1;
+	}
+
+	len = scnprintf(buf, *sz, "\n");
+	buf += len;
+	*sz -= len;
+
+	if (p->height) {
+		for_each_set_bit(i, (unsigned long *)&p->bitmap, KSYNCMAP) {
+			buf = __sync_print(__sync_child(p)[i], buf, sz,
+					   depth + 1,
+					   last << 1 | !!(p->bitmap >> (i + 1)),
+					   i);
+		}
+	}
+
+	return buf;
+}
+
+static bool
+i915_syncmap_print_to_buf(struct i915_syncmap *p, char *buf, unsigned long sz)
+{
+	if (!p)
+		return false;
+
+	while (p->parent)
+		p = p->parent;
+
+	__sync_print(p, buf, &sz, 0, 1, 0);
+	return true;
+}
+
+static int check_syncmap_free(struct i915_syncmap **sync)
+{
+	i915_syncmap_free(sync);
+	if (*sync) {
+		pr_err("sync not cleared after free\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int dump_syncmap(struct i915_syncmap *sync, int err)
+{
+	char *buf;
+
+	if (!err)
+		return check_syncmap_free(&sync);
+
+	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buf)
+		goto skip;
+
+	if (i915_syncmap_print_to_buf(sync, buf, PAGE_SIZE))
+		pr_err("%s", buf);
+
+	kfree(buf);
+
+skip:
+	i915_syncmap_free(&sync);
+	return err;
+}
+
+static int igt_syncmap_init(void *arg)
+{
+	struct i915_syncmap *sync = (void *)~0ul;
+
+	/*
+	 * Cursory check that we can initialise a random pointer and transform
+	 * it into the root pointer of a syncmap.
+	 */
+
+	i915_syncmap_init(&sync);
+	return check_syncmap_free(&sync);
+}
+
+static int check_seqno(struct i915_syncmap *leaf, unsigned int idx, u32 seqno)
+{
+	if (leaf->height) {
+		pr_err("%s: not a leaf, height is %d\n",
+		       __func__, leaf->height);
+		return -EINVAL;
+	}
+
+	if (__sync_seqno(leaf)[idx] != seqno) {
+		pr_err("%s: seqno[%d], found %x, expected %x\n",
+		       __func__, idx, __sync_seqno(leaf)[idx], seqno);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int check_one(struct i915_syncmap **sync, u64 context, u32 seqno)
+{
+	int err;
+
+	err = i915_syncmap_set(sync, context, seqno);
+	if (err)
+		return err;
+
+	if ((*sync)->height) {
+		pr_err("Inserting first context=%llx did not return leaf (height=%d, prefix=%llx\n",
+		       context, (*sync)->height, (*sync)->prefix);
+		return -EINVAL;
+	}
+
+	if ((*sync)->parent) {
+		pr_err("Inserting first context=%llx created branches!\n",
+		       context);
+		return -EINVAL;
+	}
+
+	if (hweight32((*sync)->bitmap) != 1) {
+		pr_err("First bitmap does not contain a single entry, found %x (count=%d)!\n",
+		       (*sync)->bitmap, hweight32((*sync)->bitmap));
+		return -EINVAL;
+	}
+
+	err = check_seqno((*sync), ilog2((*sync)->bitmap), seqno);
+	if (err)
+		return err;
+
+	if (!i915_syncmap_is_later(sync, context, seqno)) {
+		pr_err("Lookup of first context=%llx/seqno=%x failed!\n",
+		       context, seqno);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int igt_syncmap_one(void *arg)
+{
+	I915_RND_STATE(prng);
+	IGT_TIMEOUT(end_time);
+	struct i915_syncmap *sync;
+	unsigned long max = 1;
+	int err;
+
+	/*
+	 * Check that inserting a new id, creates a leaf and only that leaf.
+	 */
+
+	i915_syncmap_init(&sync);
+
+	do {
+		u64 context = i915_prandom_u64_state(&prng);
+		unsigned long loop;
+
+		err = check_syncmap_free(&sync);
+		if (err)
+			goto out;
+
+		for (loop = 0; loop <= max; loop++) {
+			err = check_one(&sync, context,
+					prandom_u32_state(&prng));
+			if (err)
+				goto out;
+		}
+		max++;
+	} while (!__igt_timeout(end_time, NULL));
+	pr_debug("%s: Completed %lu single insertions\n",
+		 __func__, max * (max - 1) / 2);
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int check_leaf(struct i915_syncmap **sync, u64 context, u32 seqno)
+{
+	int err;
+
+	err = i915_syncmap_set(sync, context, seqno);
+	if (err)
+		return err;
+
+	if ((*sync)->height) {
+		pr_err("Inserting context=%llx did not return leaf (height=%d, prefix=%llx\n",
+		       context, (*sync)->height, (*sync)->prefix);
+		return -EINVAL;
+	}
+
+	if (hweight32((*sync)->bitmap) != 1) {
+		pr_err("First entry into leaf (context=%llx) does not contain a single entry, found %x (count=%d)!\n",
+		       context, (*sync)->bitmap, hweight32((*sync)->bitmap));
+		return -EINVAL;
+	}
+
+	err = check_seqno((*sync), ilog2((*sync)->bitmap), seqno);
+	if (err)
+		return err;
+
+	if (!i915_syncmap_is_later(sync, context, seqno)) {
+		pr_err("Lookup of first entry context=%llx/seqno=%x failed!\n",
+		       context, seqno);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int igt_syncmap_join_above(void *arg)
+{
+	struct i915_syncmap *sync;
+	unsigned int pass, order;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * When we have a new id that doesn't fit inside the existing tree,
+	 * we need to add a new layer above.
+	 *
+	 * 1: 0x00000001
+	 * 2: 0x00000010
+	 * 3: 0x00000100
+	 * 4: 0x00001000
+	 * ...
+	 * Each pass the common prefix shrinks and we have to insert a join.
+	 * Each join will only contain two branches, the latest of which
+	 * is always a leaf.
+	 *
+	 * If we then reuse the same set of contexts, we expect to build an
+	 * identical tree.
+	 */
+	for (pass = 0; pass < 3; pass++) {
+		for (order = 0; order < 64; order += SHIFT) {
+			u64 context = BIT_ULL(order);
+			struct i915_syncmap *join;
+
+			err = check_leaf(&sync, context, 0);
+			if (err)
+				goto out;
+
+			join = sync->parent;
+			if (!join) /* very first insert will have no parents */
+				continue;
+
+			if (!join->height) {
+				pr_err("Parent with no height!\n");
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (hweight32(join->bitmap) != 2) {
+				pr_err("Join does not have 2 children: %x (%d)\n",
+				       join->bitmap, hweight32(join->bitmap));
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (__sync_child(join)[__sync_branch_idx(join, context)] != sync) {
+				pr_err("Leaf misplaced in parent!\n");
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_join_below(void *arg)
+{
+	struct i915_syncmap *sync;
+	unsigned int step, order, idx;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * Check that we can split a compacted branch by replacing it with
+	 * a join.
+	 */
+	for (step = 0; step < KSYNCMAP; step++) {
+		for (order = 64 - SHIFT; order > 0; order -= SHIFT) {
+			u64 context = step * BIT_ULL(order);
+
+			err = i915_syncmap_set(&sync, context, 0);
+			if (err)
+				goto out;
+
+			if (sync->height) {
+				pr_err("Inserting context=%llx (order=%d, step=%d) did not return leaf (height=%d, prefix=%llx\n",
+				       context, order, step, sync->height, sync->prefix);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+
+	for (step = 0; step < KSYNCMAP; step++) {
+		for (order = SHIFT; order < 64; order += SHIFT) {
+			u64 context = step * BIT_ULL(order);
+
+			if (!i915_syncmap_is_later(&sync, context, 0)) {
+				pr_err("1: context %llx (order=%d, step=%d) not found\n",
+				       context, order, step);
+				err = -EINVAL;
+				goto out;
+			}
+
+			for (idx = 1; idx < KSYNCMAP; idx++) {
+				if (i915_syncmap_is_later(&sync, context + idx, 0)) {
+					pr_err("1: context %llx (order=%d, step=%d) should not exist\n",
+					       context + idx, order, step);
+					err = -EINVAL;
+					goto out;
+				}
+			}
+		}
+	}
+
+	for (order = SHIFT; order < 64; order += SHIFT) {
+		for (step = 0; step < KSYNCMAP; step++) {
+			u64 context = step * BIT_ULL(order);
+
+			if (!i915_syncmap_is_later(&sync, context, 0)) {
+				pr_err("2: context %llx (order=%d, step=%d) not found\n",
+				       context, order, step);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_neighbours(void *arg)
+{
+	I915_RND_STATE(prng);
+	IGT_TIMEOUT(end_time);
+	struct i915_syncmap *sync;
+	int err;
+
+	/*
+	 * Each leaf holds KSYNCMAP seqno. Check that when we create KSYNCMAP
+	 * neighbouring ids, they all fit into the same leaf.
+	 */
+
+	i915_syncmap_init(&sync);
+	do {
+		u64 context = i915_prandom_u64_state(&prng) & ~MASK;
+		unsigned int idx;
+
+		if (i915_syncmap_is_later(&sync, context, 0)) /* Skip repeats */
+			continue;
+
+		for (idx = 0; idx < KSYNCMAP; idx++) {
+			err = i915_syncmap_set(&sync, context + idx, 0);
+			if (err)
+				goto out;
+
+			if (sync->height) {
+				pr_err("Inserting context=%llx did not return leaf (height=%d, prefix=%llx\n",
+				       context, sync->height, sync->prefix);
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (sync->bitmap != BIT(idx + 1) - 1) {
+				pr_err("Inserting neighbouring context=0x%llx+%d, did not fit into the same leaf bitmap=%x (%d), expected %lx (%d)\n",
+				       context, idx,
+				       sync->bitmap, hweight32(sync->bitmap),
+				       BIT(idx + 1) - 1, idx + 1);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	} while (!__igt_timeout(end_time, NULL));
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_compact(void *arg)
+{
+	struct i915_syncmap *sync;
+	unsigned int idx, order;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * The syncmap are "space efficient" compressed radix trees - any
+	 * branch with only one child is skipped and replaced by the child.
+	 *
+	 * If we construct a tree with ids that are neighbouring at a non-zero
+	 * height, we form a join but each child of that join is directly a
+	 * leaf holding the single id.
+	 */
+	for (order = SHIFT; order < 64; order += SHIFT) {
+		err = check_syncmap_free(&sync);
+		if (err)
+			goto out;
+
+		/* Create neighbours in the parent */
+		for (idx = 0; idx < KSYNCMAP; idx++) {
+			u64 context = idx * BIT_ULL(order) + idx;
+
+			err = i915_syncmap_set(&sync, context, 0);
+			if (err)
+				goto out;
+
+			if (sync->height) {
+				pr_err("Inserting context=%llx (order=%d, idx=%d) did not return leaf (height=%d, prefix=%llx\n",
+				       context, order, idx,
+				       sync->height, sync->prefix);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+
+		sync = sync->parent;
+		if (sync->parent) {
+			pr_err("Parent (join) of last leaf was not the sync!\n");
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (sync->height != order) {
+			pr_err("Join does not have the expected height, found %d, expected %d\n",
+			       sync->height, order);
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (sync->bitmap != BIT(KSYNCMAP) - 1) {
+			pr_err("Join is not full!, found %x (%d) expected %lx (%d)\n",
+			       sync->bitmap, hweight32(sync->bitmap),
+			       BIT(KSYNCMAP) - 1, KSYNCMAP);
+			err = -EINVAL;
+			goto out;
+		}
+
+		/* Each of our children should be a leaf */
+		for (idx = 0; idx < KSYNCMAP; idx++) {
+			struct i915_syncmap *leaf = __sync_child(sync)[idx];
+
+			if (leaf->height) {
+				pr_err("Child %d is a not leaf!\n", idx);
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (leaf->parent != sync) {
+				pr_err("Child %d is not attached to us!\n",
+				       idx);
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (!is_power_of_2(leaf->bitmap)) {
+				pr_err("Child %d holds more than one id, found %x (%d)\n",
+				       idx, leaf->bitmap, hweight32(leaf->bitmap));
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (leaf->bitmap != BIT(idx)) {
+				pr_err("Child %d has wrong seqno idx, found %d, expected %d\n",
+				       idx, ilog2(leaf->bitmap), idx);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_random(void *arg)
+{
+	I915_RND_STATE(prng);
+	IGT_TIMEOUT(end_time);
+	struct i915_syncmap *sync;
+	unsigned long count, phase, i;
+	u32 seqno;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * Having tried to test the individual operations within i915_syncmap,
+	 * run a smoketest exploring the entire u64 space with random
+	 * insertions.
+	 */
+
+	count = 0;
+	phase = jiffies + HZ/100 + 1;
+	do {
+		u64 context = i915_prandom_u64_state(&prng);
+
+		err = i915_syncmap_set(&sync, context, 0);
+		if (err)
+			goto out;
+
+		count++;
+	} while (!time_after(jiffies, phase));
+	seqno = 0;
+
+	phase = 0;
+	do {
+		I915_RND_STATE(ctx);
+		u32 last_seqno = seqno;
+		bool expect;
+
+		seqno = prandom_u32_state(&prng);
+		expect = seqno_later(last_seqno, seqno);
+
+		for (i = 0; i < count; i++) {
+			u64 context = i915_prandom_u64_state(&ctx);
+
+			if (i915_syncmap_is_later(&sync, context, seqno) != expect) {
+				pr_err("context=%llu, last=%u this=%u did not match expectation (%d)\n",
+				       context, last_seqno, seqno, expect);
+				err = -EINVAL;
+				goto out;
+			}
+
+			err = i915_syncmap_set(&sync, context, seqno);
+			if (err)
+				goto out;
+		}
+
+		phase++;
+	} while (!__igt_timeout(end_time, NULL));
+	pr_debug("Completed %lu passes, each of %lu contexts\n", phase, count);
+out:
+	return dump_syncmap(sync, err);
+}
+
+int i915_syncmap_mock_selftests(void)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_syncmap_init),
+		SUBTEST(igt_syncmap_one),
+		SUBTEST(igt_syncmap_join_above),
+		SUBTEST(igt_syncmap_join_below),
+		SUBTEST(igt_syncmap_neighbours),
+		SUBTEST(igt_syncmap_compact),
+		SUBTEST(igt_syncmap_random),
+	};
+
+	return i915_subtests(tests, NULL);
+}