drm/i915: Rework execbuffer pinning

Avoid evicting buffers that will be used later in the batch in order to
make room for the initial buffers by pinning all bound buffers in a
single pass before binding (and evicting for) fresh buffer.

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

1 files changed, 58 insertions, 23 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 465e07abf5d0..061426e1bbf4 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3531,44 +3531,75 @@ i915_gem_execbuffer_reserve(struct drm_device *dev,
         struct drm_i915_private *dev_priv = dev->dev_private;
         int ret, i, retry;
 
-        /* attempt to pin all of the buffers into the GTT */
+        /* Attempt to pin all of the buffers into the GTT.
+         * This is done in 3 phases:
+         *
+         * 1a. Unbind all objects that do not match the GTT constraints for
+         *     the execbuffer (fenceable, mappable, alignment etc).
+         * 1b. Increment pin count for already bound objects.
+         * 2.  Bind new objects.
+         * 3.  Decrement pin count.
+         *
+         * This avoid unnecessary unbinding of later objects in order to makr
+         * room for the earlier objects *unless* we need to defragment.
+         */
         retry = 0;
         do {
                 ret = 0;
+
+                /* Unbind any ill-fitting objects or pin. */
                 for (i = 0; i < count; i++) {
-                        struct drm_i915_gem_exec_object2 *entry = &exec_list[i];
                         struct drm_i915_gem_object *obj = object_list[i];
-                        bool need_fence =
+                        struct drm_i915_gem_exec_object2 *entry = &exec_list[i];
+                        bool need_fence, need_mappable;
+
+                        if (!obj->gtt_space)
+                                continue;
+
+                        need_fence =
                                 entry->flags & EXEC_OBJECT_NEEDS_FENCE &&
                                 obj->tiling_mode != I915_TILING_NONE;
-
-                        /* g33/pnv can't fence buffers in the unmappable part */
-                        bool need_mappable =
+                        need_mappable =
                                 entry->relocation_count ? true : need_fence;
 
-                        /* Check fence reg constraints and rebind if necessary */
-                        if (need_mappable && !obj->map_and_fenceable) {
+                        if ((entry->alignment && obj->gtt_offset & (entry->alignment - 1)) ||
+                            (need_mappable && !obj->map_and_fenceable))
                                 ret = i915_gem_object_unbind(obj);
+                        else
+                                ret = i915_gem_object_pin(obj,
+                                                          entry->alignment,
+                                                          need_mappable);
+                        if (ret) {
+                                count = i;
+                                goto err;
+                        }
+                }
+
+                /* Bind fresh objects */
+                for (i = 0; i < count; i++) {
+                        struct drm_i915_gem_exec_object2 *entry = &exec_list[i];
+                        struct drm_i915_gem_object *obj = object_list[i];
+                        bool need_fence;
+
+                        need_fence =
+                                entry->flags & EXEC_OBJECT_NEEDS_FENCE &&
+                                obj->tiling_mode != I915_TILING_NONE;
+
+                        if (!obj->gtt_space) {
+                                bool need_mappable =
+                                        entry->relocation_count ? true : need_fence;
+
+                                ret = i915_gem_object_pin(obj,
+                                                          entry->alignment,
+                                                          need_mappable);
                                 if (ret)
                                         break;
                         }
 
-                        ret = i915_gem_object_pin(obj,
-                                                  entry->alignment,
-                                                  need_mappable);
-                        if (ret)
-                                break;
-
-                        /*
-                         * Pre-965 chips need a fence register set up in order
-                         * to properly handle blits to/from tiled surfaces.
-                         */
                         if (need_fence) {
                                 ret = i915_gem_object_get_fence_reg(obj, true);
-                                if (ret) {
-                                        i915_gem_object_unpin(obj);
+                                if (ret)
                                         break;
-                                }
 
                                 dev_priv->fence_regs[obj->fence_reg].gpu = true;
                         }
@@ -3576,8 +3607,12 @@ i915_gem_execbuffer_reserve(struct drm_device *dev,
                         entry->offset = obj->gtt_offset;
                 }
 
-                while (i--)
-                        i915_gem_object_unpin(object_list[i]);
+err:            /* Decrement pin count for bound objects */
+                for (i = 0; i < count; i++) {
+                        struct drm_i915_gem_object *obj = object_list[i];
+                        if (obj->gtt_space)
+                                i915_gem_object_unpin(obj);
+                }
 
                 if (ret != -ENOSPC || retry > 1)
                         return ret;