From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Friesen Subject: Re: intel 82599 multi-port performance Date: Tue, 27 Sep 2011 16:57:33 -0600 Message-ID: <4E8254DD.6020908@genband.com> References: <4E805359.2080600@gmail.com> <4E808A41.8040902@genband.com> <4E809D59.10103@gmail.com> <4E80A2AB.2040206@intel.com> <4E811C8E.8020508@gmail.com> <4E820486.4090204@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "J.Hwan Kim" , netdev To: Alexander Duyck Return-path: Received: from exprod7og113.obsmtp.com ([64.18.2.179]:42579 "EHLO exprod7og113.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752039Ab1I0W7T (ORCPT ); Tue, 27 Sep 2011 18:59:19 -0400 In-Reply-To: <4E820486.4090204@intel.com> Sender: netdev-owner@vger.kernel.org List-ID: 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@genband.com www.genband.com