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Date: Sat, 01 Feb 2003 12:40:20 -0500
From: Jeff Garzik <jgarzik@pobox.com>
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To: Joakim Tjernlund <Joakim.Tjernlund@lumentis.se>
CC: linux-kernel@vger.kernel.org
Subject: Re: NETIF_F_SG question
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Joakim Tjernlund wrote:
> I am thinking of implementing harware scatter/gatter support( NETIF_F_SG) in my 
> ethernet driver. The network device cannot do HW checksuming.
> 
> Will the IP stack make use of the SG support and will there be any significant performance
> improvement?


No; you need HW checksumming for NETIF_F_SG to be useful.

If HW checksumming is not available, scatter-gather is useless, because 
the net stack must always make a pass over the data to checksum it. 
Since it must do that, it can linearize the skb at the same time, 
eliminating the need for SG.

	Jeff



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