drm/i915: Early rejection of mappable GGTT pin attempts for large bo

Currently, we reject attempting to pin a large bo into the mappable
aperture, but only after trying to create the vma. Under debug kernels,
repeatedly creating and freeing that vma for an oversized bo consumes
one-third of the runtime for pwrite/pread tests as it is spent on
kmalloc/kfree tracking. If we move the rejection to before creating that
vma, we lose some accuracy of checking against the fence_size as opposed
to object size, though the fence can never be smaller than the object.
Note that the vma creation itself will reject an attempt to create a vma
larger than the GTT so we can remove one redundant test.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171009084401.29090-7-chris@chris-wilson.co.ukReviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/i915_gem.c

@@ -4036,16 +4036,7 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 
 	lockdep_assert_held(&obj->base.dev->struct_mutex);
 
-	vma = i915_vma_instance(obj, vm, view);
-	if (unlikely(IS_ERR(vma)))
-		return vma;
-
-	if (i915_vma_misplaced(vma, size, alignment, flags)) {
-		if (flags & PIN_NONBLOCK &&
-		    (i915_vma_is_pinned(vma) || i915_vma_is_active(vma)))
-			return ERR_PTR(-ENOSPC);
-
-		if (flags & PIN_MAPPABLE) {
+	if (!view && flags & PIN_MAPPABLE) {
 		/* If the required space is larger than the available
 		 * aperture, we will not able to find a slot for the
 		 * object and unbinding the object now will be in
@@ -4053,7 +4044,7 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 		 * the object in and out of the Global GTT and
 		 * waste a lot of cycles under the mutex.
 		 */
-			if (vma->fence_size > dev_priv->ggtt.mappable_end)
+		if (obj->base.size > dev_priv->ggtt.mappable_end)
 			return ERR_PTR(-E2BIG);
 
 		/* If NONBLOCK is set the caller is optimistically
@@ -4072,6 +4063,20 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 		 * we could try to minimise harm to others.
 		 */
 		if (flags & PIN_NONBLOCK &&
+		    obj->base.size > dev_priv->ggtt.mappable_end / 2)
+			return ERR_PTR(-ENOSPC);
+	}
+
+	vma = i915_vma_instance(obj, vm, view);
+	if (unlikely(IS_ERR(vma)))
+		return vma;
+
+	if (i915_vma_misplaced(vma, size, alignment, flags)) {
+		if (flags & PIN_NONBLOCK) {
+			if (i915_vma_is_pinned(vma) || i915_vma_is_active(vma))
+				return ERR_PTR(-ENOSPC);
+
+			if (flags & PIN_MAPPABLE &&
 			    vma->fence_size > dev_priv->ggtt.mappable_end / 2)
 				return ERR_PTR(-ENOSPC);
 		}