From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kok, Auke" Subject: Re: e1000 full-duplex TCP performance well below wire speed Date: Thu, 31 Jan 2008 10:47:42 -0800 Message-ID: <47A217CE.4000002@intel.com> References: <36D9DB17C6DE9E40B059440DB8D95F52044F81DF@orsmsx418.amr.corp.intel.com> <36D9DB17C6DE9E40B059440DB8D95F52044F8BA3@orsmsx418.amr.corp.intel.com> <47A20E9E.7070503@intel.com> <47A215A8.2090104@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Bruce Allen , "Brandeburg, Jesse" , netdev@vger.kernel.org, Carsten Aulbert , Henning Fehrmann , Bruce Allen To: Rick Jones Return-path: Received: from mga02.intel.com ([134.134.136.20]:55628 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758160AbYAaSu6 (ORCPT ); Thu, 31 Jan 2008 13:50:58 -0500 In-Reply-To: <47A215A8.2090104@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: Rick Jones wrote: >> A lot of people tend to forget that the pci-express bus has enough >> bandwidth on >> first glance - 2.5gbit/sec for 1gbit of traffix, but apart from data >> going over it >> there is significant overhead going on: each packet requires transmit, >> cleanup and >> buffer transactions, and there are many irq register clears per second >> (slow >> ioread/writes). The transactions double for TCP ack processing, and >> this all >> accumulates and starts to introduce latency, higher cpu utilization >> etc... > > Sounds like tools to show PCI* bus utilization would be helpful... that would be a hardware profiling thing and highly dependent on the part sticking out of the slot, vendor bus implementation etc... Perhaps Intel has some tools for this already but I personally do not know of any :/ Auke