Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932259AbYAaP63 (ORCPT ); Thu, 31 Jan 2008 10:58:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760611AbYAaP6R (ORCPT ); Thu, 31 Jan 2008 10:58:17 -0500 Received: from trinity.phys.uwm.edu ([129.89.57.159]:47475 "EHLO trinity.phys.uwm.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758666AbYAaP6O (ORCPT ); Thu, 31 Jan 2008 10:58:14 -0500 Date: Thu, 31 Jan 2008 09:57:40 -0600 (CST) From: Bruce Allen X-X-Sender: ballen@trinity.phys.uwm.edu To: David Acker cc: Bill Fink , SANGTAE HA , Linux Kernel Mailing List , netdev@vger.kernel.org, Stephen Hemminger Subject: Re: e1000 full-duplex TCP performance well below wire speed In-Reply-To: <47A1E026.2070805@roinet.com> Message-ID: References: <20080130.055333.192844925.davem@davemloft.net> <20080130082136.1017631d@deepthought> <649aecc70801301617m6331bcb8i8ce60366e182c739@mail.gmail.com> <20080131064533.ef0ae932.billfink@mindspring.com> <47A1E026.2070805@roinet.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 991 Lines: 23 Hi David, > Could this be an issue with pause frames? At a previous job I remember > having issues with a similar configuration using two broadcom sb1250 3 > gigE port devices. If I ran bidirectional tests on a single pair of > ports connected via cross over, it was slower than when I gave each > direction its own pair of ports. The problem turned out to be that > pause frame generation and handling was not configured correctly. We had PAUSE frames turned off for our testing. The idea is to let TCP do the flow and congestion control. The problem with PAUSE+TCP is that it can cause head-of-line blocking, where a single oversubscribed output port on a switch can PAUSE a large number of flows on other paths. Cheers, Bruce -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/