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Message-ID: <4E8254DD.6020908@genband.com>
Date: Tue, 27 Sep 2011 16:57:33 -0600
From: Chris Friesen <chris.friesen@...band.com>
To: Alexander Duyck <alexander.h.duyck@...el.com>
CC: "J.Hwan Kim" <frog1120@...il.com>, netdev <netdev@...r.kernel.org>
Subject: Re: intel 82599 multi-port performance
On 09/27/2011 11:14 AM, Alexander Duyck wrote:
> This more or less confirms what I was thinking. You are likely hitting
> the PCIe limits of the adapters. The overhead for 64 byte packets is too
> great and as a result you are exceeding the PCIe bandwidth available to
> the adapter. In order to achieve line rate on both ports you would
> likely need to increase your packet size to something along the lines of
> 256 bytes so that the additional PCIe overhead only contributes 50% or
> less to the total PCIe traffic across the bus. Then the 2.5Gb/s of
> network traffic should consume less than 4.0GT/s of PCIe traffic.
For some further information, according to the information here:
http://shader.kaist.edu/packetshader/io_engine/benchmark/i3.html
a dual-port 82599 controller with an i3 CPU can in fact handle sending
*or* receiving (and then dropping) full line rate on both ports for
minimum-sized packets. It can't do both though. The CPU used in tose
tests isn't the greatest however, so it's tough to say where the
bottleneck is.
Chris
--
Chris Friesen
Software Developer
GENBAND
chris.friesen@...band.com
www.genband.com
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