From owner-freebsd-net@FreeBSD.ORG Sat Sep 23 07:38:38 2006 Return-Path: X-Original-To: freebsd-net@FreeBSD.org 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 4679716A40F; Sat, 23 Sep 2006 07:38:38 +0000 (UTC) (envelope-from dwmalone@maths.tcd.ie) Received: from salmon.maths.tcd.ie (salmon.maths.tcd.ie [134.226.81.11]) by mx1.FreeBSD.org (Postfix) with SMTP id A0BE543D45; Sat, 23 Sep 2006 07:38:36 +0000 (GMT) (envelope-from dwmalone@maths.tcd.ie) Received: from walton.maths.tcd.ie ([134.226.81.10] helo=walton.maths.tcd.ie) by salmon.maths.tcd.ie with SMTP id ; 23 Sep 2006 08:38:35 +0100 (BST) Date: Sat, 23 Sep 2006 08:38:33 +0100 From: David Malone To: Robert Watson Message-ID: <20060923073833.GA10269@walton.maths.tcd.ie> References: <4511B9B1.2000903@freebsd.org> <17683.63162.919620.114649@grasshopper.cs.duke.edu> <45145F1D.8020005@freebsd.org> <20060922234708.V11343@fledge.watson.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060922234708.V11343@fledge.watson.org> User-Agent: Mutt/1.5.6i Sender: dwmalone@maths.tcd.ie Cc: Andre Oppermann , Andrew Gallatin , alc@FreeBSD.org, freebsd-net@FreeBSD.org, freebsd-current@FreeBSD.org, tegge@FreeBSD.org Subject: Re: Much improved sendfile(2) kernel implementation X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 23 Sep 2006 07:38:38 -0000 On Fri, Sep 22, 2006 at 11:48:23PM +0100, Robert Watson wrote: > The impact of TSO is clearly dramatic, especially when combined with the > patch, but I'm a bit concerned by the drop in performance in the patched > non-TSO case. For network cards which will always have TSO enabled, this > isn't an issue, but do we see a similar affect for drivers without TSO? > What can we put this drop down to? We probably also need to make sure that any performance increase in TSO isn't due to us getting TCP congestion control wrong. I think in Linux they had problems when they first introduced TSO because TCP was advancing the congestion window by a TSO-sized chunk instead of a wire packet. OTOH, I think Andre and Drew's tests are low-latency, so congestion control isn't likely to be playing a big role, so the improvements are unlikely to be due to this. David.