drm/i915: Split batch pool into size buckets

Now with the trimmed memcpy before the command parser, we try to
allocate many different sizes of batches, predominantly one or two
pages. We can therefore speed up searching for a good sized batch by
keeping the objects of buckets of roughly the same size.

v2: Add a comment about bucket sizes

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 31 insertions, 18 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_batch_pool.c b/drivers/gpu/drm/i915/i915_gem_batch_pool.c
index 1287abf55b84..7bf2f3f2968e 100644
--- a/drivers/gpu/drm/i915/i915_gem_batch_pool.c
+++ b/drivers/gpu/drm/i915/i915_gem_batch_pool.c
@@ -47,8 +47,12 @@
 void i915_gem_batch_pool_init(struct drm_device *dev,
 			      struct i915_gem_batch_pool *pool)
 {
+	int n;
+
 	pool->dev = dev;
-	INIT_LIST_HEAD(&pool->cache_list);
+
+	for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++)
+		INIT_LIST_HEAD(&pool->cache_list[n]);
 }
 
 /**
@@ -59,16 +63,20 @@ void i915_gem_batch_pool_init(struct drm_device *dev,
  */
 void i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool)
 {
+	int n;
+
 	WARN_ON(!mutex_is_locked(&pool->dev->struct_mutex));
 
-	while (!list_empty(&pool->cache_list)) {
-		struct drm_i915_gem_object *obj =
-			list_first_entry(&pool->cache_list,
-					 struct drm_i915_gem_object,
-					 batch_pool_list);
+	for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++) {
+		while (!list_empty(&pool->cache_list[n])) {
+			struct drm_i915_gem_object *obj =
+				list_first_entry(&pool->cache_list[n],
+						 struct drm_i915_gem_object,
+						 batch_pool_link);
 
-		list_del(&obj->batch_pool_list);
-		drm_gem_object_unreference(&obj->base);
+			list_del(&obj->batch_pool_link);
+			drm_gem_object_unreference(&obj->base);
+		}
 	}
 }
 
@@ -91,28 +99,33 @@ i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
 {
 	struct drm_i915_gem_object *obj = NULL;
 	struct drm_i915_gem_object *tmp, *next;
+	struct list_head *list;
+	int n;
 
 	WARN_ON(!mutex_is_locked(&pool->dev->struct_mutex));
 
-	list_for_each_entry_safe(tmp, next,
-				 &pool->cache_list, batch_pool_list) {
+	/* Compute a power-of-two bucket, but throw everything greater than
+	 * 16KiB into the same bucket: i.e. the the buckets hold objects of
+	 * (1 page, 2 pages, 4 pages, 8+ pages).
+	 */
+	n = fls(size >> PAGE_SHIFT) - 1;
+	if (n >= ARRAY_SIZE(pool->cache_list))
+		n = ARRAY_SIZE(pool->cache_list) - 1;
+	list = &pool->cache_list[n];
+
+	list_for_each_entry_safe(tmp, next, list, batch_pool_link) {
 		/* The batches are strictly LRU ordered */
 		if (tmp->active)
 			break;
 
 		/* While we're looping, do some clean up */
 		if (tmp->madv == __I915_MADV_PURGED) {
-			list_del(&tmp->batch_pool_list);
+			list_del(&tmp->batch_pool_link);
 			drm_gem_object_unreference(&tmp->base);
 			continue;
 		}
 
-		/*
-		 * Select a buffer that is at least as big as needed
-		 * but not 'too much' bigger. A better way to do this
-		 * might be to bucket the pool objects based on size.
-		 */
-		if (tmp->base.size >= size && tmp->base.size <= 2 * size) {
+		if (tmp->base.size >= size) {
 			obj = tmp;
 			break;
 		}
@@ -132,7 +145,7 @@ i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
 		obj->madv = I915_MADV_DONTNEED;
 	}
 
-	list_move_tail(&obj->batch_pool_list, &pool->cache_list);
+	list_move_tail(&obj->batch_pool_link, list);
 	i915_gem_object_pin_pages(obj);
 	return obj;
 }