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From:   Andi Kleen <ak@muc.de>
To:     Andrew Morton <morton@nortelnetworks.com>
Cc:     "David S. Miller" <davem@redhat.com>,
        Pekka Pietikainen <pp@evil.netppl.fi>, netdev@oss.sgi.com
Subject: Re: zerocopy results on GigE
References: <20010206194919.A633@netppl.fi> <14976.28256.593782.781889@pizda.ninka.net> <3A809569.A9313C6F@asiapacificm01.nt.com>
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In-Reply-To: <3A809569.A9313C6F@asiapacificm01.nt.com>; from Andrew Morton on Wed, Feb 07, 2001 at 01:25:14AM +0100
Date:   Wed, 7 Feb 2001 10:45:21 +0100
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On Wed, Feb 07, 2001 at 01:25:14AM +0100, Andrew Morton wrote:
> "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?

You can check all that by reading the TCP_INFO socket option from
inside the process after a gap occurs.

It unfortunately does not work from outside the process currently, except
with some dirty unsafe hacks for socket /proc open. 


-Andi