Messages in this thread | | | Date | Mon, 4 May 2009 17:14:08 +0200 | From | Matthias Saou <> | Subject | Wrong network usage reported by /proc |
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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
-- 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 : 0.39 0.30 0.34
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