From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH 1/1] cbq: incorrect processing of high limits Date: Mon, 01 Apr 2013 09:24:36 -0700 Message-ID: <1364833476.5113.157.camel@edumazet-glaptop> References: <5159852C.8060003@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Alexey Kuznetsov , "David S. Miller" , Jamal Hadi Salim To: Vasily Averin Return-path: Received: from mail-pa0-f47.google.com ([209.85.220.47]:54722 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751875Ab3DAQYi (ORCPT ); Mon, 1 Apr 2013 12:24:38 -0400 Received: by mail-pa0-f47.google.com with SMTP id bj3so1392321pad.34 for ; Mon, 01 Apr 2013 09:24:38 -0700 (PDT) In-Reply-To: <5159852C.8060003@parallels.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2013-04-01 at 17:01 +0400, Vasily Averin wrote: > currently cbq works incorrectly for limits > 10% real link bandwidth, > and practically does not work for limits > 50% real link bandwidth. > Below are results of experiments taken on 1 Gbit link > > In shaper | Actual Result > -----------+--------------- > 100M | 108 Mbps > 200M | 244 Mbps > 300M | 412 Mbps > 500M | 893 Mbps > > This happen because of q->now changes incorrectly in cbq_dequeue(): > when it is called before real end of packet transmitting, > L2T is greater than real time delay, q_now gets an extra boost > but never compensate it. > > To fix this problem we prevent change of q->now until its synchronization > with real time. > > Signed-off-by: Vasily Averin > Reviewed-by: Alexey Kuznetsov > --- > net/sched/sch_cbq.c | 5 ++++- > 1 files changed, 4 insertions(+), 1 deletions(-) > > diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c > index 6aabd77..5b5c83a 100644 > --- a/net/sched/sch_cbq.c > +++ b/net/sched/sch_cbq.c > @@ -962,8 +962,11 @@ cbq_dequeue(struct Qdisc *sch) > cbq_update(q); > if ((incr -= incr2) < 0) > incr = 0; > + q->now += incr; > + } else { > + if (now > q->now) > + q->now = now; > } > - q->now += incr; > q->now_rt = now; > > for (;;) { Acked-by: Eric Dumazet Still, after your patch a limit of 500Mbit gives : rate 515872Kbit 946pps backlog 0b 2p requeues 0 HTB is more precise : rate 500667Kbit 41336pps backlog 0b 2p requeues 0