From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] Disable TSO for non standard qdiscs Date: Fri, 1 Feb 2008 09:24:39 -0800 Message-ID: <20080201092439.7c588ef5@extreme> References: <20080131100846.00934e25@extreme> <20080131185328.GD4671@one.firstfloor.org> <47A211A0.1040502@trash.net> <20080131190125.GE4671@one.firstfloor.org> <20080131193406.GH4671@one.firstfloor.org> <1201847738.17656.5.camel@roma.44ansell.gdt.id.au> <20080201074600.GA12644@one.firstfloor.org> <47A2C985.30409@trash.net> <20080201143421.GB16630@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: "Waskiewicz Jr, Peter P" , Patrick McHardy , Andi Kleen , Glen Turner , netdev@vger.kernel.org To: Andi Kleen Return-path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:47657 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755781AbYBARZX (ORCPT ); Fri, 1 Feb 2008 12:25:23 -0500 In-Reply-To: <20080201143421.GB16630@one.firstfloor.org> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 1 Feb 2008 15:34:21 +0100 Andi Kleen wrote: > > The TSO defer logic is based on your congestion window and current > > window size. So the actual frame sizes hitting your NIC attached to > > your DSL probably aren't anywhere near 64KB, but probably more in line > > with whatever your window size is for DSL. > > DSL windows can be quite large because a lot of DSL lines have a quite > long latency due to error correction. And with ADSL2 we have upto 16Mbit > now. > > > I think we're having more of a disagreement of what is considered the > > "normal case" user. If you are on a slow link, such as a DSL/cable > > line, your TCP window/congestion window aren't going to be big enough to > > generate large TSO's, so what is the issue? But disabling TSO, say on a > > 64k TSOs are likely even with DSL. Anyways even with smaller TSOs the > change still makes sense because each increase makes packet scheduling > less smooth. > > -Andi I wish there was a per-device setting for the max-size of TSO burst. -- Stephen Hemminger