From owner-freebsd-net@FreeBSD.ORG Mon Jul 26 20:29:00 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 5EEE916A4CE for ; Mon, 26 Jul 2004 20:29:00 +0000 (GMT) Received: from mail.sandvine.com (sandvine.com [199.243.201.138]) by mx1.FreeBSD.org (Postfix) with ESMTP id D892643D45 for ; Mon, 26 Jul 2004 20:28:59 +0000 (GMT) (envelope-from don@sandvine.com) Received: by mail.sandvine.com with Internet Mail Service (5.5.2657.72) id ; Mon, 26 Jul 2004 16:28:59 -0400 Message-ID: From: Don Bowman To: 'Luigi Rizzo' , Kelly Yancey Date: Mon, 26 Jul 2004 16:28:56 -0400 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2657.72) Content-Type: text/plain; charset="iso-8859-1" cc: freebsd-net@freebsd.org cc: 'James' 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: Mon, 26 Jul 2004 20:29:00 -0000 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. --don