netdev - Re: [PATCH] net: optimise csum

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Message-Id: <20140926.161436.2294622951811354901.davem@davemloft.net>
Date:	Fri, 26 Sep 2014 16:14:36 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	christophe.leroy@....fr
Cc:	linux-kernel@...r.kernel.org, edumazet@...gle.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] net: optimise csum_replace4()

From: Christophe Leroy <christophe.leroy@....fr>
Date: Tue, 23 Sep 2014 10:54:32 +0200 (CEST)

> csum_partial() is a generic function which is not optimised for small fixed
> length calculations, and its use requires to store "from" and "to" values in
> memory while we already have them available in registers. This also has impact,
> especially on RISC processors. In the same spirit as the change done by
> Eric Dumazet on csum_replace2(), this patch rewrites inet_proto_csum_replace4()
> taking into account RFC1624.
> 
> I spotted during a NATted tcp transfert that csum_partial() is one of top 5
> consuming functions (around 8%), and the second user of csum_partial() is 
> inet_proto_csum_replace4().
> 
> I have proposed the same modification to inet_proto_csum_replace4() in another
> patch.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

Applied.
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