From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Furniss Subject: Re: [PATCH 2/7] ATM cell alignment. Date: Sun, 13 Apr 2008 12:24:41 +0100 Message-ID: <4801ED79.5090502@andyfurniss.entadsl.com> References: Reply-To: lists@andyfurniss.entadsl.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , netdev , "David S. Miller" , Patrick McHardy To: Jesper Dangaard Brouer Return-path: Received: from mx1.ukfsn.org ([77.75.108.10]:34119 "EHLO mail.ukfsn.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755742AbYDMLYp (ORCPT ); Sun, 13 Apr 2008 07:24:45 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Jesper Dangaard Brouer wrote: > + The align to ATM cells is used for determining the (ATM) SAR > + alignment overhead at the ATM layer. (SAR = Segmentation And > + Reassembly). This is for example needed when scheduling packet on an > + ADSL connection. Note that the extra ATM-AAL overhead is _not_ > + included in this calculation. This overhead is added in the kernel > + before doing the rate table lookup, as this gives better precision > + (as the table will always be aligned for 48 bytes). I see overhead is unsigned short. For me using pppoa/vc mux my overhead is IP + 10. I am shaping on eth so skb->len is IP+14 hence I need a negative overhead. Recently built a 2.6.25-rc7 and noticed the cell_align has been added and the tables jigged. I am (ab)using this at -5 now. Handy that I only need to patch TC rather than kernel and I guess I could use other TCs if I needed to shape other not atm ifs. Russel Stuart's patches handled this case IIRC, has it been lost or have I missed something (as usual)? Andy.