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Re: zerocopy results on GigE

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: zerocopy results on GigE
From: "Andrew Morton" <morton@xxxxxxxxxxxxxxxxxx>
Date: Wed, 07 Feb 2001 02:05:56 +0000
Cc: Pekka Pietikainen <pp@xxxxxxxxxxxxxx>, netdev@xxxxxxxxxxx
Organization: Nortel Networks, Wollongong Australia
References: <3A809569.A9313C6F@xxxxxxxxxxxxxxxxxxxxx>, <20010206194919.A633@xxxxxxxxx> <14976.28256.593782.781889@xxxxxxxxxxxxxxx> <3A809569.A9313C6F@xxxxxxxxxxxxxxxxxxxxx> <14976.39500.484616.490586@xxxxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
"David S. Miller" wrote:
> 
> Andrew Morton writes:
>  > "David S. Miller" wrote:
>  > >
>  > > Strange, cpu usage is close to nothing for sendfile cases yet full
>  > > bandwidth is not obtained.
>  >
>  > Is it possible that the receiver is going into discard,
>  > and TCP is backing off?
> 
> Or even worse, the Gige cards are emitting flow control frames.
> 

What would trigger that behaviour?  Presumably, the lack
of any Rx DMA descriptors.

It would be interesting to bump up acenic's RX_RING_SIZE and
friends, as well as the backlog queue.

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