drm/i915: Track the purgeable objects on a separate eviction list

Currently the purgeable objects, I915_MADV_DONTNEED, are mixed in the
normal bound/unbound lists. Every shrinker pass starts with an attempt
to purge from this set of unneeded objects, which entails us doing a
walk over both lists looking for any candidates. If there are none, and
since we are shrinking we can reasonably assume that the lists are
full!, this becomes a very slow futile walk.

If we separate out the purgeable objects into own list, this search then
becomes its own phase that is preferentially handled during shrinking.
Instead the cost becomes that we then need to filter the purgeable list
if we want to distinguish between bound and unbound objects.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190530203500.26272-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_domain.c

@@ -462,7 +462,6 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 static void i915_gem_object_bump_inactive_ggtt(struct drm_i915_gem_object *obj)
 {
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
-	struct list_head *list;
 	struct i915_vma *vma;
 
 	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
@@ -476,10 +475,15 @@ static void i915_gem_object_bump_inactive_ggtt(struct drm_i915_gem_object *obj)
 	}
 	mutex_unlock(&i915->ggtt.vm.mutex);
 
+	if (obj->mm.madv == I915_MADV_WILLNEED) {
+		struct list_head *list;
+
 		spin_lock(&i915->mm.obj_lock);
-	list = obj->bind_count ? &i915->mm.bound_list : &i915->mm.unbound_list;
+		list = obj->bind_count ?
+			&i915->mm.bound_list : &i915->mm.unbound_list;
 		list_move_tail(&obj->mm.link, list);
 		spin_unlock(&i915->mm.obj_lock);
+	}
 }
 
 void

drivers/gpu/drm/i915/gem/i915_gem_object.c

@@ -333,9 +333,18 @@ void i915_gem_free_object(struct drm_gem_object *gem_obj)
 	if (obj->mm.quirked)
 		__i915_gem_object_unpin_pages(obj);
 
-	if (discard_backing_storage(obj))
+	if (discard_backing_storage(obj)) {
+		struct drm_i915_private *i915 = to_i915(obj->base.dev);
+
 		obj->mm.madv = I915_MADV_DONTNEED;
 
+		if (i915_gem_object_has_pages(obj)) {
+			spin_lock(&i915->mm.obj_lock);
+			list_move_tail(&obj->mm.link, &i915->mm.purge_list);
+			spin_unlock(&i915->mm.obj_lock);
+		}
+	}
+
 	/*
 	 * Before we free the object, make sure any pure RCU-only
 	 * read-side critical sections are complete, e.g.

drivers/gpu/drm/i915/gem/i915_gem_pm.c

@@ -164,6 +164,7 @@ void i915_gem_suspend_late(struct drm_i915_private *i915)
 	struct list_head *phases[] = {
 		&i915->mm.unbound_list,
 		&i915->mm.bound_list,
+		&i915->mm.purge_list,
 		NULL
 	}, **phase;
 

drivers/gpu/drm/i915/gem/i915_gem_shmem.c

@@ -80,9 +80,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
 	sg_page_sizes = 0;
 	for (i = 0; i < page_count; i++) {
 		const unsigned int shrink[] = {
-			(I915_SHRINK_BOUND |
-			 I915_SHRINK_UNBOUND |
-			 I915_SHRINK_PURGEABLE),
+			I915_SHRINK_BOUND | I915_SHRINK_UNBOUND,
 			0,
 		}, *s = shrink;
 		gfp_t gfp = noreclaim;

drivers/gpu/drm/i915/gem/i915_gem_shrinker.c

@@ -144,6 +144,7 @@ i915_gem_shrink(struct drm_i915_private *i915,
 		struct list_head *list;
 		unsigned int bit;
 	} phases[] = {
+		{ &i915->mm.purge_list, ~0u },
 		{ &i915->mm.unbound_list, I915_SHRINK_UNBOUND },
 		{ &i915->mm.bound_list, I915_SHRINK_BOUND },
 		{ NULL, 0 },
@@ -226,10 +227,6 @@ i915_gem_shrink(struct drm_i915_private *i915,
 						       mm.link))) {
 			list_move_tail(&obj->mm.link, &still_in_list);
 
-			if (flags & I915_SHRINK_PURGEABLE &&
-			    obj->mm.madv != I915_MADV_DONTNEED)
-				continue;
-
 			if (flags & I915_SHRINK_VMAPS &&
 			    !is_vmalloc_addr(obj->mm.mapping))
 				continue;
@@ -239,6 +236,10 @@ i915_gem_shrink(struct drm_i915_private *i915,
 			     i915_gem_object_is_framebuffer(obj)))
 				continue;
 
+			if (!(flags & I915_SHRINK_BOUND) &&
+			    READ_ONCE(obj->bind_count))
+				continue;
+
 			if (!can_release_pages(obj))
 				continue;
 
@@ -324,6 +325,11 @@ i915_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 			count += obj->base.size >> PAGE_SHIFT;
 			num_objects++;
 		}
+	list_for_each_entry(obj, &i915->mm.purge_list, mm.link)
+		if (!i915_gem_object_is_active(obj) && can_release_pages(obj)) {
+			count += obj->base.size >> PAGE_SHIFT;
+			num_objects++;
+		}
 	spin_unlock(&i915->mm.obj_lock);
 
 	/* Update our preferred vmscan batch size for the next pass.
@@ -361,14 +367,6 @@ i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 				&sc->nr_scanned,
 				I915_SHRINK_BOUND |
 				I915_SHRINK_UNBOUND |
-				I915_SHRINK_PURGEABLE |
-				I915_SHRINK_WRITEBACK);
-	if (sc->nr_scanned < sc->nr_to_scan)
-		freed += i915_gem_shrink(i915,
-					 sc->nr_to_scan - sc->nr_scanned,
-					 &sc->nr_scanned,
-					 I915_SHRINK_BOUND |
-					 I915_SHRINK_UNBOUND |
 				I915_SHRINK_WRITEBACK);
 	if (sc->nr_scanned < sc->nr_to_scan && current_is_kswapd()) {
 		intel_wakeref_t wakeref;

drivers/gpu/drm/i915/i915_drv.h

@@ -864,6 +864,10 @@ struct i915_gem_mm {
 	 * not actually have any pages attached.
 	 */
 	struct list_head unbound_list;
+	/**
+	 * List of objects which are purgeable. May be active.
+	 */
+	struct list_head purge_list;
 
 	/** List of all objects in gtt_space, currently mmaped by userspace.
 	 * All objects within this list must also be on bound_list.
@@ -2865,12 +2869,12 @@ unsigned long i915_gem_shrink(struct drm_i915_private *i915,
 			      unsigned long target,
 			      unsigned long *nr_scanned,
 			      unsigned flags);
-#define I915_SHRINK_PURGEABLE	BIT(0)
-#define I915_SHRINK_UNBOUND	BIT(1)
-#define I915_SHRINK_BOUND	BIT(2)
-#define I915_SHRINK_ACTIVE	BIT(3)
-#define I915_SHRINK_VMAPS	BIT(4)
-#define I915_SHRINK_WRITEBACK	BIT(5)
+#define I915_SHRINK_UNBOUND	BIT(0)
+#define I915_SHRINK_BOUND	BIT(1)
+#define I915_SHRINK_ACTIVE	BIT(2)
+#define I915_SHRINK_VMAPS	BIT(3)
+#define I915_SHRINK_WRITEBACK	BIT(4)
+
 unsigned long i915_gem_shrink_all(struct drm_i915_private *i915);
 void i915_gem_shrinker_register(struct drm_i915_private *i915);
 void i915_gem_shrinker_unregister(struct drm_i915_private *i915);

drivers/gpu/drm/i915/i915_gem.c

@@ -1095,7 +1095,7 @@ int
 i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 		       struct drm_file *file_priv)
 {
-	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_i915_private *i915 = to_i915(dev);
 	struct drm_i915_gem_madvise *args = data;
 	struct drm_i915_gem_object *obj;
 	int err;
@@ -1118,7 +1118,7 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 
 	if (i915_gem_object_has_pages(obj) &&
 	    i915_gem_object_is_tiled(obj) &&
-	    dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
+	    i915->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
 		if (obj->mm.madv == I915_MADV_WILLNEED) {
 			GEM_BUG_ON(!obj->mm.quirked);
 			__i915_gem_object_unpin_pages(obj);
@@ -1134,6 +1134,20 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 	if (obj->mm.madv != __I915_MADV_PURGED)
 		obj->mm.madv = args->madv;
 
+	if (i915_gem_object_has_pages(obj)) {
+		struct list_head *list;
+
+		spin_lock(&i915->mm.obj_lock);
+		if (obj->mm.madv != I915_MADV_WILLNEED)
+			list = &i915->mm.purge_list;
+		else if (obj->bind_count)
+			list = &i915->mm.bound_list;
+		else
+			list = &i915->mm.unbound_list;
+		list_move_tail(&obj->mm.link, list);
+		spin_unlock(&i915->mm.obj_lock);
+	}
+
 	/* if the object is no longer attached, discard its backing storage */
 	if (obj->mm.madv == I915_MADV_DONTNEED &&
 	    !i915_gem_object_has_pages(obj))
@@ -1750,6 +1764,7 @@ static void i915_gem_init__mm(struct drm_i915_private *i915)
 
 	init_llist_head(&i915->mm.free_list);
 
+	INIT_LIST_HEAD(&i915->mm.purge_list);
 	INIT_LIST_HEAD(&i915->mm.unbound_list);
 	INIT_LIST_HEAD(&i915->mm.bound_list);
 	INIT_LIST_HEAD(&i915->mm.fence_list);
@@ -1844,6 +1859,7 @@ int i915_gem_freeze_late(struct drm_i915_private *i915)
 			i915_gem_object_unlock(obj);
 		}
 	}
+	GEM_BUG_ON(!list_empty(&i915->mm.purge_list));
 
 	return 0;
 }

drivers/gpu/drm/i915/i915_vma.c

@@ -717,7 +717,8 @@ i915_vma_remove(struct i915_vma *vma)
 		struct drm_i915_gem_object *obj = vma->obj;
 
 		spin_lock(&i915->mm.obj_lock);
-		if (--obj->bind_count == 0)
+		if (--obj->bind_count == 0 &&
+		    obj->mm.madv == I915_MADV_WILLNEED)
 			list_move_tail(&obj->mm.link, &i915->mm.unbound_list);
 		spin_unlock(&i915->mm.obj_lock);