Re: NETIF_F_SG question

From: Joakim Tjernlund (Joakim.Tjernlund@lumentis.se)
Date: Sat Feb 01 2003 - 13:42:01 EST


> 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

linearize = copy small buffers inte one big buffer, or?
Surley the copy operation will cost something?

 Jocke
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