From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756194AbZEEID3 (ORCPT ); Tue, 5 May 2009 04:03:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753012AbZEEIDB (ORCPT ); Tue, 5 May 2009 04:03:01 -0400 Received: from mx32b01.es6.egwn.net ([195.10.6.123]:57992 "EHLO mx1.es6.egwn.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752588AbZEEIDA (ORCPT ); Tue, 5 May 2009 04:03:00 -0400 Date: Tue, 5 May 2009 10:02:58 +0200 From: Matthias Saou To: Robert Hancock Cc: linux-kernel@vger.kernel.org Subject: Re: Wrong network usage reported by /proc Message-ID: <20090505100258.68d90754@python3.es.egwn.lan> In-Reply-To: <49FFC489.6080402@gmail.com> References: <20090504171408.3e13822c@python3.es.egwn.lan> <49FFC489.6080402@gmail.com> X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Robert Hancock wrote : > Matthias Saou wrote: > > Hi, > > > > I'm posting here as a last resort. I've got lots of heavily used RHEL5 > > servers (2.6.18 based) that are reporting all sorts of impossible > > network usage values through /proc, leading to unrealistic snmp/cacti > > graphs where the outgoing bandwidth used it higher than the physical > > interface's maximum speed. > > > > For some details and a test script which compares values from /proc > > with values from tcpdump : > > https://bugzilla.redhat.com/show_bug.cgi?id=489541 > > > > The values collected using tcpdump always seem realistic and match the > > values seen on the remote network equipments. So my obvious conclusion > > (but possibly wrong given my limited knowledge) is that something is > > wrong in the kernel, since it's the one exposing the /proc interface. > > > > I've reproduced what seems to be the same problem on recent kernels, > > including the 2.6.27.21-170.2.56.fc10.x86_64 I'm running right now. The > > simple python script available here allows to see it quite easily : > > https://www.redhat.com/archives/rhelv5-list/2009-February/msg00166.html > > > > * I run the script on my Workstation, I have an FTP server enabled > > * I download a DVD ISO from a remote workstation : The values match > > * I start ping floods from remote workstations : The values reported > > by /proc are much higher than the ones reported by tcpdump. I used > > "ping -s 500 -f myworkstation" from two remote workstations > > > > If there's anything flawed in my debugging, I'd love to have someone > > point it out to me. TIA to anyone willing to have a look. > > > > Matthias > > > > There may well be a bug in the kernel you're using, but you'd likely > have more luck reporting a bug to Red Hat - the RHEL5 kernel is quite > old and heavily patched and not many LKML people will likely be familiar > with what RH may have done to it.. I've already reported it to Red Hat (through Dell), and have an open ticket. But I only have basic support, so I have no idea if/when a problem like this will get escalated to someone with enough knowledge. But I seem to have been able to reproduce the issue on very recent 2.6 kernels, with different chips/drivers which is why I'm posting here. Matthias -- Clean custom Red Hat Linux rpm packages : http://freshrpms.net/ Fedora release 10 (Cambridge) - Linux kernel 2.6.27.21-170.2.56.fc10.x86_64 Load : 0.10 0.06 0.01