[Intel-gfx] [PATCH 23/27] drm/i915: First try the previous execbuffer location

[Chris Wilson]

When choosing a slot for an execbuffer, we ideally want to use the same
address as last time (so that we don't have to rebind it) and the same
address as expected by the user (so that we don't have to fixup any
relocations pointing to it). If we first try to bind the incoming
execbuffer->offset from the user, or the currently bound offset that
should hopefully achieve the goal of avoiding the rebind cost and the
relocation penalty. However, if the object is not currently bound there
we don't want to arbitrarily unbind an object in our chosen position and
so choose to rebind/relocate the incoming object instead. After we
report the new position back to the user, on the next pass the
relocations should have settled down.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtien at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 12 ++++++++----
 drivers/gpu/drm/i915/i915_gem_gtt.c        |  6 ++++++
 drivers/gpu/drm/i915/i915_gem_gtt.h        |  1 +
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index de41e423d3f7..f4b5e221708d 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -329,10 +329,15 @@ eb_pin_vma(struct i915_execbuffer *eb,
 {
 	u64 flags;
 
-	flags = vma->node.start;
-	flags |= PIN_USER | PIN_NONBLOCK | PIN_OFFSET_FIXED;
+	if (vma->node.size)
+		flags = vma->node.start;
+	else
+		flags = entry->offset & PIN_OFFSET_MASK;
+
+	flags |= PIN_USER | PIN_NOEVICT | PIN_OFFSET_FIXED;
 	if (unlikely(entry->flags & EXEC_OBJECT_NEEDS_GTT))
 		flags |= PIN_GLOBAL;
+
 	if (unlikely(i915_vma_pin(vma, 0, 0, flags)))
 		return;
 
@@ -460,8 +465,7 @@ eb_add_vma(struct i915_execbuffer *eb,
 		entry->flags |= eb->context_flags;
 
 	err = 0;
-	if (vma->node.size)
-		eb_pin_vma(eb, entry, vma);
+	eb_pin_vma(eb, entry, vma);
 	if (eb_vma_misplaced(entry, vma)) {
 		eb_unreserve_vma(vma, entry);
 
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 8bab4aea63e6..62871cd50605 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3288,6 +3288,9 @@ int i915_gem_gtt_reserve(struct i915_address_space *vm,
 	if (err != -ENOSPC)
 		return err;
 
+	if (flags & PIN_NOEVICT)
+		return -ENOSPC;
+
 	err = i915_gem_evict_for_node(vm, node, flags);
 	if (err == 0)
 		err = drm_mm_reserve_node(&vm->mm, node);
@@ -3402,6 +3405,9 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,
 	if (err != -ENOSPC)
 		return err;
 
+	if (flags & PIN_NOEVICT)
+		return -ENOSPC;
+
 	/* No free space, pick a slot at random.
 	 *
 	 * There is a pathological case here using a GTT shared between
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index fb15684c1d83..a528ce1380fd 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -588,6 +588,7 @@ int i915_gem_gtt_insert(struct i915_address_space *vm,
 #define PIN_MAPPABLE		BIT(1)
 #define PIN_ZONE_4G		BIT(2)
 #define PIN_NONFAULT		BIT(3)
+#define PIN_NOEVICT		BIT(4)
 
 #define PIN_MBZ			BIT(5) /* I915_VMA_PIN_OVERFLOW */
 #define PIN_GLOBAL		BIT(6) /* I915_VMA_GLOBAL_BIND */
-- 
2.11.0