From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: tc linklayer ADSL calc broken after commit 56b765b79 (htb: improved accuracy at high rates) Date: Wed, 29 May 2013 08:52:04 -0700 Message-ID: <1369842724.5109.44.camel@edumazet-glaptop> References: <20130529151330.22c5c89e@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , David Miller , j.vimal@gmail.com, Michal Soltys , Mike Frysinger , Jussi Kivilinna , Patrick McHardy , Jiri Pirko , Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= , Dave Taht , netdev@vger.kernel.org, bloat@lists.bufferbloat.net, Dan Siemon , Jim Gettys , Steven Barth , Felix Fietkau , Jiri Benc To: Jesper Dangaard Brouer Return-path: Received: from mail-pd0-f178.google.com ([209.85.192.178]:60009 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932934Ab3E2PwH (ORCPT ); Wed, 29 May 2013 11:52:07 -0400 Received: by mail-pd0-f178.google.com with SMTP id w11so6036159pde.37 for ; Wed, 29 May 2013 08:52:06 -0700 (PDT) In-Reply-To: <20130529151330.22c5c89e@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2013-05-29 at 15:13 +0200, Jesper Dangaard Brouer wrote: > I recently discovered that the (traffic control) tc linklayer > calculations for ATM/ADSL have been broken by: > commit 56b765b79 (htb: improved accuracy at high rates). > > Thus, people shaping on ADSL links, using e.g.: > tc class add ... htb rate X ceil Y linklayer atm overhead 10 > > Will no-longer get ATM cell tax/overhead adjusted. > > How can we solve/fix this? > Perhaps we can change to use the "stab" system instead (as it does > not seem to be broken by the commit). > > But how do we facilitate a change to use "stab" system (for all the > scripts using the old option)? > > Can we change the iproute2/tc command to handle this transparently, or > should we give an error/warning if someone uses "tc" and "linklayer" on > a kernel above v.3.8. ? > > > History: > - My linklayer ATM changes appeared in kernel 2.6.24 (and iproute2 2.6.25) > - The STAB changes appeared in kernel 2.6.27 > Hi Jesper stab suffers from the same problem : its table driven, so works only for packet smaller than a given size. I am not sure it will solve the ATM logic (with the 5 bytes overhead per 48 bytes cell) btw, even on old kernels :