Messages in this thread | | | Date | Tue, 5 May 2009 10:02:58 +0200 | From | Matthias Saou <> | Subject | Re: Wrong network usage reported by /proc |
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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
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