drm/i915: Only bump refcnt on objects scheduled for eviction

Incrementing the reference count on all objects walked when searching
for space in the aperture is a non-neglible amount of overhead. In fact,
we only need to hold on to a reference for objects that we will evict,
so we can therefore delay the referencing until we find a suitable hole
and only add those objects that fall inside.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index 097119c..6ba4be5 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -36,7 +36,6 @@ static bool
 mark_free(struct drm_i915_gem_object *obj, struct list_head *unwind)
 {
        list_add(&obj->exec_list, unwind);
-       drm_gem_object_reference(&obj->base);
        return drm_mm_scan_add_block(obj->gtt_space);
 }
 
@@ -139,7 +138,6 @@ i915_gem_evict_something(struct drm_device *dev, int min_size,
                BUG_ON(ret);
 
                list_del_init(&obj->exec_list);
-               drm_gem_object_unreference(&obj->base);
        }
 
        /* We expect the caller to unpin, evict all and try again, or give up.
@@ -158,10 +156,10 @@ found:
                                       exec_list);
                if (drm_mm_scan_remove_block(obj->gtt_space)) {
                        list_move(&obj->exec_list, &eviction_list);
+                       drm_gem_object_reference(&obj->base);
                        continue;
                }
                list_del_init(&obj->exec_list);
-               drm_gem_object_unreference(&obj->base);
        }
 
        /* Unbinding will emit any required flushes */