Re: [PATCH 1/8] rbtree: Cache leftmost node internally

[Jan Kara <jack@suse.cz>]

On Fri 09-06-17 07:32:50, Davidlohr Bueso wrote:
> >>@@ -150,6 +161,7 @@ extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
> >>
> >> static __always_inline struct rb_node *
> >> __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
> >>+		     struct rb_node **leftmost,
> >> 		     const struct rb_augment_callbacks *augment)
> >> {
> >> 	struct rb_node *child = node->rb_right;
> >>@@ -157,6 +169,9 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
> >> 	struct rb_node *parent, *rebalance;
> >> 	unsigned long pc;
> >>
> >>+	if (leftmost && node == *leftmost)
> >>+		*leftmost = rb_next(node);
> >>+
> >> 	if (!tmp) {
> >> 		/*
> >> 		 * Case 1: node to erase has no more than 1 child (easy!)
> >
> >Why do you propagate e.g. 'leftmost' down to __rb_erase_augmented() when
> >you could just handle everything within rb_erase_augmented_cached?
> >Similarly for other functions like __rb_insert()... It would seem like less
> >churn and I don't see downside to it...
> 
> I propagate args so we don't have to duplicate the checks between the regular
> and augmented rbtrees.

OK, yeah. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR