netdev - Re: [PATCH 3/6] IPV4 : use xor rather than multiple ands for route compare

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Date:	Thu, 10 Apr 2008 21:17:46 +0900 (JST)
From:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
To:	davem@...emloft.net
Cc:	shemminger@...tta.com, dada1@...mosbay.com, netdev@...r.kernel.org,
	yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH 3/6] IPV4 : use xor rather than multiple ands for route
 compare

In article <20080410.035618.217931997.davem@...emloft.net> (at Thu, 10 Apr 2008 03:56:18 -0700 (PDT)), David Miller <davem@...emloft.net> says:

> Branch prediction fares very poorly in such cases, and
> therefore it is better to mispredict one branch over
> all the data items in the same cache line than any one
> of several such branches.  The above new sequence gets
> emitted by the compiler as several integer operations and
> one branch.  As long as all the data items are in the
> same cacheline, this is optimal.

Okay, thanks.

--yoshfuji
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