linux-kernel - Re: [PATCH v2 8/9] rbtree: faster augmented rbtree manipulation

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Date:	Sun, 05 Aug 2012 22:12:34 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Michel Lespinasse <walken@...gle.com>
CC:	peterz@...radead.org, daniel.santos@...ox.com, aarcange@...hat.com,
	dwmw2@...radead.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH v2 8/9] rbtree: faster augmented rbtree manipulation

On 08/02/2012 06:34 PM, Michel Lespinasse wrote:
> Introduce new augmented rbtree APIs that allow minimal recalculation of
> augmented node information.
>
> A new callback is added to the rbtree insertion and erase rebalancing
> functions, to be called on each tree rotations. Such rotations preserve
> the subtree's root augmented value, but require recalculation of the one
> child that was previously located at the subtree root.
>
> In the insertion case, the handcoded search phase must be updated to
> maintain the augmented information on insertion, and then the rbtree
> coloring/rebalancing algorithms keep it up to date.
>
> In the erase case, things are more complicated since it is library
> code that manipulates the rbtree in order to remove internal nodes.
> This requires a couple additional callbacks to copy a subtree's
> augmented value when a new root is stitched in, and to recompute
> augmented values down the ancestry path when a node is removed from
> the tree.
>
> In order to preserve maximum speed for the non-augmented case,
> we provide two versions of each tree manipulation function.
> rb_insert_augmented() is the augmented equivalent of rb_insert_color(),
> and rb_erase_augmented() is the augmented equivalent of rb_erase().
>
> Signed-off-by: Michel Lespinasse<walken@...gle.com>

Acked-by: Rik van Riel <riel@...hat.com>

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