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Re: [Xen-users] Heavy Dom0 traffic stops network



Fajar A. Nugraha wrote:

On Mon, Feb 1, 2010 at 6:37 PM, Simon Hobson <linux@xxxxxxxxxxxxxxxx> wrote:
 However, it's not just traffic from Dom0 to DomU that does it. I've got a
 big transfer going from another machine copying large amounts of data to the
 same DomU - and ping is showing occasional dropped packets.


 So, anyone got hints on what;s causing it, and more importantly, how to fix
 it ?

Do you have traffic limit somewhere? It sounds like the switch your
physical machine connected to has port storm-control or similar. I'd
suggest testing using crossover cable from server <-> laptop and use
iperf (or other packet generators) to isolate the problem.

It's definitely not that - when not transferring data between Dom0 and DomU on the same machine, I can shovel data around between DomUs and external partners with no problem.

The problem ONLY happens when Dom0 is exchanging data with a DomU it hosts. It's completely repeatable - start large transfer and wait, when the traffic stops I can hit ctrl-C and the network comes back to life.

So passing network traffic about is fine as long as Dom0 isn't involved at anything (other than a low rate) with one of it's own DomUs - I had to limit my rsync transfer to 25kbyte/s and even then it could cause a problem if there was other traffic going on.

Given bits I've picked up before, I'm guessing that there's a problem in the network handling process - one thread handling all traffic ? Wild stab in the dark, but it does sound a bit like some sort of mutual blocking going on - and stopping one partner then frees the other one up.

Is this something I should report as a bug ? What's the right way to do that ? Unfortunately, I don't have another non-production machine available at the moment so it's a bit difficult trying the later version from Debian Squeeze. I'll have a rummage around tomorrow, but I don't think anything has enough RAM.

--
Simon Hobson

WANTED: "Software CD ROM Kit" for Canon CLBP 360-PS printer (Canon part no RH6-3612, or possibly RH6-3810, or RH6-3610 might do). I've a dead HD and need this CD so I can replace the disk and re-install the printer OS on it. If anyone knows where I might get hold of one I'd be grateful - requests to Canon drew a blank, it's been out of support for years. Alternatively, if anyone has one of these and would let me image their hard disk ...

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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