[PATCH 2/2] drm/mm: improve rb_hole_addr rbtree search

[Chris Wilson]

Quoting Nirmoy Das (2020-05-19 09:44:36)
> +#define DRM_MM_ALIGN_SHIFT 6
>  #define HOLE_SIZE(NODE) ((NODE)->hole_size)
>  #define HOLE_ADDR(NODE) (__drm_mm_hole_node_start(NODE))
> +#define HOLE_SIZE_ALIGN(NODE) ((NODE->hole_size << DRM_MM_ALIGN_SHIFT) | \
> +                              ffs(HOLE_ADDR(NODE)))

Fwiw, max hole size of 58b, we would need to stop storing byte
extents...

>  static struct drm_mm_node *
> -next_hole_low_addr(struct drm_mm_node *entry, u64 size)
> +next_hole_low_addr(struct drm_mm_node *entry, u64 size, u64 alignment)
>  {
>         struct rb_node *rb_node, *right_rb_node, *parent_rb_node;
>         struct drm_mm_node *right_node;
> +       u64 req_align = (size + alignment) << DRM_MM_ALIGN_SHIFT;
>  
>         if (!entry)
>                 return NULL;
> @@ -513,6 +561,7 @@ next_hole_low_addr(struct drm_mm_node *entry, u64 size)
>                 right_node = rb_entry(right_rb_node,
>                                       struct drm_mm_node, rb_hole_addr);
>                 if ((right_node->subtree_max_hole < size ||
> +                    right_node->subtree_max_hole_align < req_align ||

What was the point in storing the packed alignment if we are just
searching for a hole big enough for (size + alignment)?
-Chris