[PATCH 3/4] drm/i915: Allow userspace to hint that the relocations were known

[Chris Wilson <chris@chris-wilson.co.uk>]

Userspace is able to hint to the kernel that its command stream and
auxiliary state buffers already hold the correct presumed addresses and
so the relocation process may be skipped if the kernel does not need to
move any buffers in preparation for the execbuffer. Thus for the common
case where the allotment of buffers is static between batches, we can
avoid the overhead of individually checking the relocation entries.

Note that this requires userspace to supply the domain tracking and
requests for workarounds itself that would otherwise be computed based
upon the relocation entries.

Using copywinwin10 as an example that is dependent upon emitting a lot
of relocations (2 per operation), we see improvements of:

c2d/gm45: 618000.0/sec to 632000.0/sec.
i3-330m: 748000.0/sec to 830000.0/sec.

(measured relative to a baseline with neither optimisations applied).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_dma.c            |    3 ++
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |   50 ++++++++++++++++++----------
 include/uapi/drm/i915_drm.h                |   11 ++++++
 3 files changed, 46 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 4beb7bc..a0c4b4f 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1017,6 +1017,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
 	case I915_PARAM_HAS_SECURE_BATCHES:
 		value = capable(CAP_SYS_ADMIN);
 		break;
+	case I915_PARAM_HAS_EXEC_NO_RELOC:
+		value = 1;
+		break;
 	default:
 		DRM_DEBUG_DRIVER("Unknown parameter %d\n",
 				 param->param);
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 1738ebd..30beea6 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -412,7 +412,8 @@ i915_gem_execbuffer_relocate(struct drm_device *dev,
 
 static int
 i915_gem_execbuffer_reserve_object(struct drm_i915_gem_object *obj,
-				   struct intel_ring_buffer *ring)
+				   struct intel_ring_buffer *ring,
+				   bool *need_reloc)
 {
 	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
 	struct drm_i915_gem_exec_object2 *entry = obj->exec_entry;
@@ -452,7 +453,18 @@ i915_gem_execbuffer_reserve_object(struct drm_i915_gem_object *obj,
 		obj->has_aliasing_ppgtt_mapping = 1;
 	}
 
-	entry->offset = obj->gtt_offset;
+	if (entry->offset != obj->gtt_offset) {
+		entry->offset = obj->gtt_offset;
+		*need_reloc = true;
+	}
+
+	obj->base.pending_read_domains = entry->rsvd1 & 0xffffffff;
+	obj->base.pending_write_domain = (entry->rsvd1 >> 32) & 0xffffffff;
+
+	if (entry->flags & EXEC_OBJECT_NEEDS_GTT &&
+	    !obj->has_global_gtt_mapping)
+		i915_gem_gtt_bind_object(obj, obj->cache_level);
+
 	return 0;
 }
 
@@ -478,7 +490,8 @@ i915_gem_execbuffer_unreserve_object(struct drm_i915_gem_object *obj)
 static int
 i915_gem_execbuffer_reserve(struct intel_ring_buffer *ring,
 			    struct drm_file *file,
-			    struct list_head *objects)
+			    struct list_head *objects,
+			    bool *need_relocs)
 {
 	struct drm_i915_gem_object *obj;
 	struct list_head ordered_objects;
@@ -502,8 +515,6 @@ i915_gem_execbuffer_reserve(struct intel_ring_buffer *ring,
 		else
 			list_move_tail(&obj->exec_list, &ordered_objects);
 
-		obj->base.pending_read_domains = 0;
-		obj->base.pending_write_domain = 0;
 		obj->pending_fenced_gpu_access = false;
 	}
 	list_splice(&ordered_objects, objects);
@@ -541,7 +552,7 @@ i915_gem_execbuffer_reserve(struct intel_ring_buffer *ring,
 			    (need_fence && !obj->map_and_fenceable))
 				ret = i915_gem_object_unbind(obj);
 			else
-				ret = i915_gem_execbuffer_reserve_object(obj, ring);
+				ret = i915_gem_execbuffer_reserve_object(obj, ring, need_relocs);
 			if (ret)
 				goto err;
 		}
@@ -551,7 +562,7 @@ i915_gem_execbuffer_reserve(struct intel_ring_buffer *ring,
 			if (obj->gtt_space)
 				continue;
 
-			ret = i915_gem_execbuffer_reserve_object(obj, ring);
+			ret = i915_gem_execbuffer_reserve_object(obj, ring, need_relocs);
 			if (ret)
 				goto err;
 		}
@@ -571,16 +582,18 @@ err:		/* Decrement pin count for bound objects */
 
 static int
 i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
+				  struct drm_i915_gem_execbuffer2 *args,
 				  struct drm_file *file,
 				  struct intel_ring_buffer *ring,
 				  struct eb_objects *eb,
-				  struct drm_i915_gem_exec_object2 *exec,
-				  int count)
+				  struct drm_i915_gem_exec_object2 *exec)
 {
 	struct drm_i915_gem_relocation_entry *reloc;
 	struct drm_i915_gem_object *obj;
+	bool need_relocs;
 	int *reloc_offset;
 	int i, total, ret;
+	int count = args->buffer_count;
 
 	/* We may process another execbuffer during the unlock... */
 	while (!list_empty(&eb->objects)) {
@@ -635,7 +648,8 @@ i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
 	if (ret)
 		goto err;
 
-	ret = i915_gem_execbuffer_reserve(ring, file, &eb->objects);
+	need_relocs = (args->flags & I915_EXEC_NO_RELOC) == 0;
+	ret = i915_gem_execbuffer_reserve(ring, file, &eb->objects, &need_relocs);
 	if (ret)
 		goto err;
 
@@ -848,10 +862,9 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	struct intel_ring_buffer *ring;
 	u32 ctx_id = i915_execbuffer2_get_context_id(*args);
 	u32 exec_start, exec_len;
-	u32 seqno;
-	u32 mask;
-	u32 flags;
+	u32 seqno, mask, flags;
 	int ret, mode, i;
+	bool need_relocs;
 
 	if (!i915_gem_check_execbuffer(args)) {
 		DRM_DEBUG("execbuf with invalid offset/length\n");
@@ -993,17 +1006,18 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 			       exec_list);
 
 	/* Move the objects en-masse into the GTT, evicting if necessary. */
-	ret = i915_gem_execbuffer_reserve(ring, file, &eb->objects);
+	need_relocs = (args->flags & I915_EXEC_NO_RELOC) == 0;
+	ret = i915_gem_execbuffer_reserve(ring, file, &eb->objects, &need_relocs);
 	if (ret)
 		goto err;
 
 	/* The objects are in their final locations, apply the relocations. */
-	ret = i915_gem_execbuffer_relocate(dev, eb);
+	if (need_relocs)
+		ret = i915_gem_execbuffer_relocate(dev, eb);
 	if (ret) {
 		if (ret == -EFAULT) {
-			ret = i915_gem_execbuffer_relocate_slow(dev, file, ring,
-								eb, exec,
-								args->buffer_count);
+			ret = i915_gem_execbuffer_relocate_slow(dev, args, file, ring,
+								eb, exec);
 			BUG_ON(!mutex_is_locked(&dev->struct_mutex));
 		}
 		if (ret)
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 067b98e..7657d3e 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -309,6 +309,7 @@ typedef struct drm_i915_irq_wait {
 #define I915_PARAM_HAS_PRIME_VMAP_FLUSH	 21
 #define I915_PARAM_RSVD_FOR_FUTURE_USE	 22
 #define I915_PARAM_HAS_SECURE_BATCHES	 23
+#define I915_PARAM_HAS_EXEC_NO_RELOC	 24
 
 typedef struct drm_i915_getparam {
 	int param;
@@ -629,7 +630,10 @@ struct drm_i915_gem_exec_object2 {
 	__u64 offset;
 
 #define EXEC_OBJECT_NEEDS_FENCE (1<<0)
+#define EXEC_OBJECT_NEEDS_GTT	(1<<1)
 	__u64 flags;
+
+	/** Low 32-bits for read-domains, high 32-bits for write-domains. */
 	__u64 rsvd1;
 	__u64 rsvd2;
 };
@@ -679,6 +683,13 @@ struct drm_i915_gem_execbuffer2 {
  */
 #define I915_EXEC_SECURE		(1<<9)
 
+/** Provide a hint to the kernel that the command stream and auxilliary
+ * state buffers already holds the correct presumed addresses and so the
+ * relocation process may be skipped if no buffers need to be moved in
+ * preparation for the execbuffer.
+ */
+#define I915_EXEC_NO_RELOC		(1<<10)
+
 #define I915_EXEC_CONTEXT_ID_MASK	(0xffffffff)
 #define i915_execbuffer2_set_context_id(eb2, context) \
 	(eb2).rsvd1 = context & I915_EXEC_CONTEXT_ID_MASK
-- 
1.7.10.4