From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Pirko Subject: Re: inaccurate packet scheduling Date: Tue, 8 Jan 2013 14:30:38 +0100 Message-ID: <20130108133038.GB1621@minipsycho.orion> References: <1355849503.9380.37.camel@edumazet-glaptop> <20130102152601.GB1532@minipsycho.orion> <1357144482.21409.16876.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: edumazet@google.com, netdev@vger.kernel.org, kuznet@ms2.inr.ac.ru, jhs@mojatatu.com To: Eric Dumazet Return-path: Received: from mail-we0-f169.google.com ([74.125.82.169]:46588 "EHLO mail-we0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756257Ab3AHNam (ORCPT ); Tue, 8 Jan 2013 08:30:42 -0500 Received: by mail-we0-f169.google.com with SMTP id t49so346008wey.14 for ; Tue, 08 Jan 2013 05:30:41 -0800 (PST) Content-Disposition: inline In-Reply-To: <1357144482.21409.16876.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: Wed, Jan 02, 2013 at 05:34:42PM CET, eric.dumazet@gmail.com wrote: >On Wed, 2013-01-02 at 16:26 +0100, Jiri Pirko wrote: >> Tue, Dec 18, 2012 at 05:51:43PM CET, erdnetdev@gmail.com wrote: >> >On Tue, 2012-12-18 at 08:26 -0800, Stephen Hemminger wrote: >> > >> >> Check kernel log for messages about clock. It could be that on the >> >> machines with issues TSC is not usable for kernel clock. >> >> Also turn off TSO since it screws up any form of rate control. >> > >> >Yes, but we should fix it eventually. I'll take a look. >> >> Hi Eric, did you have a chance to look at this? Or should I give it a try? > >I took a look, and TBF does : > >if (qdisc_pkt_len(skb) > q->max_size) > return qdisc_reshape_fail(skb, sch); > >We have several choices : > >1) Add a one time warning > >2) cap dev->gso_max_size at Qdisc setup time > >3) Re-segment the packet instead of dropping it (if GSO packet), and >call the expensive qdisc_tree_decrease_qlen() function. > >4) remove max_size limitation > To my untrained eye, 2) or 4) look like a way to go. Not sure though.