[Intel-gfx] [PATCH 46/64] drm/i915: Count how many VMA are bound for an object

[Chris Wilson]

On Tue, Jul 12, 2016 at 03:30:25PM +0100, Tvrtko Ursulin wrote:
> On 07/07/16 09:41, Chris Wilson wrote:
> >@@ -3684,6 +3684,9 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> >  					    old_read_domains,
> >  					    old_write_domain);
> >
> >+	/* Increment the pages_pin_count to guard against the shrinker */
> >+	obj->pages_pin_count++;
> 
> Would it be clearer to look at obj->pin_display in the shrinker?
> Although it looks like special casing out of the cleanliness of the
> design in both case so I am not sure.

Yeah. I liked the mechanism of telling the shrinker to avoid certain
pages by only having to control the pages_pin_count. It feels easier to
explain to others "the shrinker may reap any object that hasn't pinned
its pages" (explicitly called i915_gem_object_pin_pages for its own use)
rather than that + plus a list of exceptions known by the shrinker.

> >@@ -82,7 +67,7 @@ static bool can_release_pages(struct drm_i915_gem_object *obj)
> >  	 * to the GPU, simply unbinding from the GPU is not going to succeed
> >  	 * in releasing our pin count on the pages themselves.
> >  	 */
> >-	if (obj->pages_pin_count != num_vma_bound(obj))
> >+	if (obj->pages_pin_count != obj->bind_count)
> 
> Would this be clearer as obj->pages_pin_count > obj->bind_count ?

Ok.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre