linux-kernel - Re: [PATCH v2 6/9] rbtree: low level optimizations in rb

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Date:	Sun, 05 Aug 2012 21:41:16 -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 6/9] rbtree: low level optimizations in rb_erase()

On 08/02/2012 06:34 PM, Michel Lespinasse wrote:
> Various minor optimizations in rb_erase():
> - Avoid multiple loading of node->__rb_parent_color when computing parent
>    and color information (possibly not in close sequence, as there might
>    be further branches in the algorithm)
> - In the 1-child subcase of case 1, copy the __rb_parent_color field from
>    the erased node to the child instead of recomputing it from the desired
>    parent and color
> - When searching for the erased node's successor, differentiate between
>    cases 2 and 3 based on whether any left links were followed. This avoids
>    a condition later down.
> - In case 3, keep a pointer to the erased node's right child so we don't
>    have to refetch it later to adjust its parent.
> - In the no-childs subcase of cases 2 and 3, place the rebalance assigment
>    last so that the compiler can remove the following if(rebalance) test.
>
> Also, added some comments to illustrate cases 2 and 3.
>
> Signed-off-by: Michel Lespinasse<walken@...gle.com>

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


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