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

[Nirmoy <nirmodas@xxxxxxx>]

Hi Chris,

On 5/20/20 12:56 AM, Chris Wilson wrote:
> 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...


Can you please explain 2nd part of this statement.


> >   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)?

Yes, I realized this is not correct :/

Still thinking about a better solution to capture alignment into subtree 
elimination.


Regards,

Nirmoy

> -Chris
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