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>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 465e07a..061426e 100644 (file)
--- 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;