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

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Message-ID: <20170612094720.GB22728@quack2.suse.cz>
Date:   Mon, 12 Jun 2017 11:47:20 +0200
From:   Jan Kara <jack@...e.cz>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     Jan Kara <jack@...e.cz>, mingo@...nel.org, peterz@...radead.org,
        akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
        ldufour@...ux.vnet.ibm.com, mhocko@...e.com,
        mgorman@...hsingularity.net, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/8] rbtree: Cache leftmost node internally

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@...e.cz>

								Honza

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