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Awful proxy_arp performance [message #36598]

Fri, 03 July 2009 15:43

tobia
Messages: 5
Registered: July 2009

Junior Member

Hi

I have the following setup:
- Debian Lenny 5.0.1
- Pre-built Debian kernel: linux-image-2.6.26-2-openvz-amd64, version 2.6.26-15
- Standard venet0 routed setup, with ip_forward and proxy_arp enabled

I'm experiencing an awful proxy_arp performance.

ARP requests from a random host on the LAN (let's call it host A) to any VE running on this server, which we'll call host B, take between zero and 800ms to complete. See a frequency graph of 1000 tests, below.

ARP requests from host A to host B (not to a VE) are near-istantaneous (<1ms) as are subsequent pings from A to the VE, after ARP resolution has taken place.

Is there a way to fix this problem without resorting to a bridged veth setup?

http://forum.openvz.org/index.php?t=getfile&id=756

In case you want to run the test on your own, here is what I did to measure the times, in Bash:

h=192.168.10.7; for ((i=0; i<1000; i++)) do sudo arp -d $h; ping -nc1 $h | awk -F'[ =]' '/bytes from/ {print $10}'; done > times.csv

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[Updated on: Fri, 03 July 2009 15:58]

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Re: Awful proxy_arp performance [message #36632 is a reply to message #36598]

Mon, 06 July 2009 10:52

tobia
Messages: 5
Registered: July 2009

Junior Member

I solved this issue using veth instead of vnet and bridging all the veth* together with eth0. Configured this way, ARP requests are back to a reasonable average of 3ms.

I would still like to know if it can be solved any other way. Isn't vnet supposed to be more efficient than veth?

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