From owner-freebsd-net@FreeBSD.ORG Tue Jul 27 02:59:00 2004 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E597C16A4CE for ; Tue, 27 Jul 2004 02:59:00 +0000 (GMT) Received: from ylpvm01.prodigy.net (ylpvm01-ext.prodigy.net [207.115.57.32]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9AC6943D31 for ; Tue, 27 Jul 2004 02:59:00 +0000 (GMT) (envelope-from kbyanc@posi.net) Received: from gateway.posi.net (adsl-63-201-93-86.dsl.snfc21.pacbell.net [63.201.93.86])i6R2wxAt024855; Mon, 26 Jul 2004 22:58:59 -0400 Received: from localhost (localhost [127.0.0.1]) by gateway.posi.net (Postfix) with ESMTP id 8043B6A047C; Mon, 26 Jul 2004 20:00:10 -0700 (PDT) Date: Mon, 26 Jul 2004 20:00:10 -0700 (PDT) From: Kelly Yancey To: Don Bowman In-Reply-To: Message-ID: <20040726195807.R76990@gateway.posi.net> References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: 'Luigi Rizzo' cc: 'James' cc: freebsd-net@freebsd.org Subject: RE: device polling takes more CPU hits?? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 27 Jul 2004 02:59:01 -0000 On Mon, 26 Jul 2004, Don Bowman wrote: > From: Luigi Rizzo [mailto:rizzo@icir.org] > > On Mon, Jul 26, 2004 at 01:18:46PM -0700, Kelly Yancey wrote: > > ... > > > Out of curiousity, what sort of testing did you do to > > arrive at these > > > settings? I did some testing a while back with a SmartBits > > box pumping > > > packets through a FreeBSD 2.8Ghz box configured to route > > between two em > > > gigabit interfaces; I found that changing the burst_max and > > each_burst > > > parameters had almost no effect on throughput (maximum 1% > > difference). > > > > fast boxes are pci-bus limited, not CPU limited(*) so > > changing the burst > > size (which basically amortizes some CPU costs) has little if any > > effect. > > The PCI-X bus will probably be 64-bit 133MHz in this case, > the limit moves up to the P64H2 hub for large packets, > to the CPU for small packets. Polling becomes quite > critical to prevent livelock. > Sorry, I should be been more clear. Polling certainly stopped livelock under extreme load, however I never found much difference whether the burst size was small or large. I was wondering if it was just the nature of my test and if in other environments the burst_max and each_burst knobs have a greater affect. Kelly -- Kelly Yancey - kbyanc@{posi.net,FreeBSD.org} - kelly@nttmcl.com FreeBSD, The Power To Serve: http://www.freebsd.org/