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Date: Wed, 1 Oct 2014 10:56:01 +0200
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Long Tran <kyle.longtran@gmail.com>
Subject: Re: Netmap - Packet generating performance changes
Message-ID: <20141001085601.GA5641@onelab2.iet.unipi.it>
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Cc: "Gurkan, Deniz" <dgurkan@central.uh.edu>,
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On Wed, Oct 01, 2014 at 03:42:06AM -0500, Long Tran wrote:
> Hello,
> 
> I am experimenting netmap and see one strange behavior.
> When I am generating packets using pkt-gen example from PC1 to PC2, the
> rate is about 3Mpps. But when I run pkg-gen -f rx -i p1p1 from PC2, the
> generating rate in PC1 goes up to 14.66Mpps.
> 
> I thought the performance of netmap in one PC didn't depend on the other
> end.
> Could anyone help explain it to me please?

flow control on the link is responsible for the slowdown.
On FreeBSD, sysctl dev.ix.0.fc=0 disables that
On Linux i think it is some ethtool command


cheers
luigi

> 
> Thanks,
> *Long Tran*
> Research Assistant
> MS in Network Communications and Technology Project Management
> University of Houston
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