drm/i915: Wire up shrinkctl->nr_scanned

shrink_slab() allows us to report back the number of objects we
successfully scanned (out of the target shrinkctl->nr_to_scan). As
report the number of pages owned by each GEM object as a separate item
to the shrinker, we cannot precisely control the number of shrinker
objects we scan on each pass; and indeed may free more than requested.
If we fail to tell the shrinker about the number of objects we process,
it will continue to hold a grudge against us as any objects left
unscanned are added to the next reclaim -- and so we will keep on
"unfairly" shrinking our own slab in comparison to other slabs.

v2: fixup the misplaced addition, we want to count everything we scan
(to match the number we reported earlier) not just the objects we
successfully validated and freed.

References: 912d572d63b8 ("drm/i915: wire up shrinkctl->nr_scanned")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013202621.7276-6-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index 065d026b5092d14f85ac27444dc3e5a2d3fd16cd..175765111f4ebfe67d9f4286151c76d715257c58 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -243,8 +243,8 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
                                        count += obj->base.size >> PAGE_SHIFT;
                                }
                                mutex_unlock(&obj->mm.lock);
-                               scanned += obj->base.size >> PAGE_SHIFT;
                        }
+                       scanned += obj->base.size >> PAGE_SHIFT;
 
                        spin_lock(&dev_priv->mm.obj_lock);
                }