From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: Early SPECWeb99 results on 2.5.33 with TSO on e1000 Date: 11 Sep 2002 03:11:49 -0600 Sender: netdev-bounce@oss.sgi.com Message-ID: References: <20020905.204721.49430679.davem@redhat.com> <18563262.1031269721@[10.10.2.3]> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , hadi@cyberus.ca, tcw@tempest.prismnet.com, linux-kernel@vger.kernel.org, netdev@oss.sgi.com, Nivedita Singhvi Return-path: To: "Martin J. Bligh" In-Reply-To: <18563262.1031269721@[10.10.2.3]> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org "Martin J. Bligh" writes: > > Ie. the headers that don't need to go across the bus are the critical > > resource saved by TSO. > > I'm not sure that's entirely true in this case - the Netfinity > 8500R is slightly unusual in that it has 3 or 4 PCI buses, and > there's 4 - 8 gigabit ethernet cards in this beast spread around > different buses (Troy - are we still just using 4? ... and what's > the raw bandwidth of data we're pushing? ... it's not huge). > > I think we're CPU limited (there's no idle time on this machine), > which is odd for an 8 CPU 900MHz P3 Xeon, Quite possibly. The P3 has roughly an 800MB/s FSB bandwidth, that must be used for both I/O and memory accesses. So just driving a gige card at wire speed takes a considerable portion of the cpus capacity. On analyzing this kind of thing I usually find it quite helpful to compute what the hardware can theoretically to get a feel where the bottlenecks should be. Eric