Maykel Moya
2012-Jan-20 10:08 UTC
Different network traffic values from dom0 and from domU
Hi, [ this is an excerpt of a question (posted by me) in serverfault http://j.mp/zzDPuV ] I''m using Xen 4.0.1 with Linux 2.6.32-5-xen-amd64 (standard packages on a Debian Squeeze system). From Xen Networking: "Think of them (vif<id#>.0 @dom0 and eth0 @domU) as two ethernet interfaces connected by an internal crossover ethernet cable." My understanding of this internal crossover thing is that networking statistics should be the same no matter if you measure it in the dom0 (vifN.N interface) or in the domU (eth0 interface). RX/TX values should be the same, just inverted. Nevertheless I''m getting ~20% larger values when traffic is measured in dom0. Just after starting the domU I ran this on the dom0: root@dev1:~# while true; do date; cat /sys/class/net/vif35.0/statistics/{r,t}x_bytes; sleep 1; done ... Thu Jan 19 13:18:00 EST 2012 4826 466049 Thu Jan 19 13:18:01 EST 2012 4826 466580 Thu Jan 19 13:18:02 EST 2012 4826 467427 Thu Jan 19 13:18:03 EST 2012 4826 467910 Thu Jan 19 13:18:04 EST 2012 4826 468769 Thu Jan 19 13:18:05 EST 2012 4826 469764 and in the domU root@node2050:~# while true; do date; cat /sys/class/net/eth0/statistics/{r,t}x_bytes; sleep 1; done ... Thu Jan 19 13:18:00 EST 2012 395229 5792 Thu Jan 19 13:18:01 EST 2012 395961 5792 Thu Jan 19 13:18:02 EST 2012 396617 5792 Thu Jan 19 13:18:03 EST 2012 397304 5792 Thu Jan 19 13:18:04 EST 2012 397735 5792 Thu Jan 19 13:18:05 EST 2012 398620 5792 Do anybody have a clue about why the values are (that) different? Is this a Xen bug? Regards, maykel