From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Furniss Subject: Re: [PATCH 2/7] ATM cell alignment. Date: Wed, 16 Apr 2008 00:41:57 +0100 Message-ID: <48053D45.40307@andyfurniss.entadsl.com> References: <4801ED79.5090502@andyfurniss.entadsl.com> 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]:43833 "EHLO mail.ukfsn.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752591AbYDOXlk (ORCPT ); Tue, 15 Apr 2008 19:41:40 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Jesper Dangaard Brouer wrote: > On Sun, 13 Apr 2008, Andy Furniss wrote: >> 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. > > I'm not completely sure I understand how you end up with a negative > overhead. But I guess what you are saying, is that you need to remove > the MAC header from the equation is it has already been added to > skb->len (as you are doing routed and not bridged AAL5 encap). Yep I think there are only two cases that will hit this one. > > That makes a good point for a _seperate_ patch (by you ;-)) where we > change the overhead to be signed. Or else you can do a userspace TC > patch that abuse the cell_align, as you mentioned below, to express a > negative overhead. (I'm trying to say, lets not mix these things... > please!) Fair enough, I suppose doing it with overhead could be more dangerous for accidental user misconfiguration than just in TC. > > >> Recently built a 2.6.25-rc7 and noticed the cell_align has been added >> and the tables jigged. > > Yes, the tables has been aligned to 2^n and avoids underestimation. > Thus, with upto 2^4 (16) the table aligns to 48 bytes (ATM cell payload > size), standard TC uses 2^3. (If I remember correctly you, did comment > on the patch so you must have read it ;-)). Hmm did I - was that the post where I wanted overhead to be bigger for ingress shaping - what is it with me and overhead :-) > > ps. I'm currently on a roadtrip down the west-coast of USA, so I only > have periodic wifi coverage at different campgrounds... Have a good holiday. Andy.