From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: iproute2-2.6.20-070313 bug ? Date: Thu, 22 Mar 2007 10:12:24 -0700 Message-ID: <20070322101224.3e6bb899@freekitty> References: <20070321175951.M73913@visp.net.lb> <46026717.9060909@trash.net> <20070322124533.M79867@visp.net.lb> <46027FF2.6020001@trash.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Denys , netdev@vger.kernel.org To: Patrick McHardy Return-path: Received: from smtp.osdl.org ([65.172.181.24]:40544 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934138AbXCVRMb (ORCPT ); Thu, 22 Mar 2007 13:12:31 -0400 In-Reply-To: <46027FF2.6020001@trash.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, 22 Mar 2007 14:09:06 +0100 Patrick McHardy wrote: > Denys wrote: > > /sbin/tc2 qdisc del dev ppp0 root > > /sbin/tc2 qdisc add dev ppp0 root handle 1: prio > > /sbin/tc2 qdisc add dev ppp0 parent 1:1 handle 2: tbf buffer 1024kb latency > > 500ms rate 128kbit peakrate 256kbit minburst 16384 > > /sbin/tc2 filter add dev ppp0 parent 1:0 protocol ip prio 10 u32 match ip dst > > 0.0.0.0/0 flowid 2:1 > > > That is an incredible huge buffer value. > > > qdisc tbf 2: parent 1:1 rate 128000bit burst 4294932937b peakrate > 256000bit minburst 16Kb lat 4.2s > > And it causes an overflow. > > The limit for the TBF burst value with nanosecond resolution is > ~ 4 * rate (10^9 * burst / rate < 2^32 needs to hold), resoluting > in a worst-case latency of 4 seconds. I think this limit is in the > reasonable range. Your configuration results in a worst-case > queuing delay of 64s, and I doubt that you really want that. > > Obviously its not good to break existing configurations, but I > would argue that this configuration is broken. > tc should check for overflows and doesn't. Do you want to make a patch for the obvious cases? -- Stephen Hemminger