Re: Kernel deadlock using nbd over acenic driver

[Peter T. Breuer]

"A month of sundays ago ptb wrote:"
> There are also several studies being made from collaborators in
> Heidelberg which show qualitative differences between new VM and old VM
> behaviour on the _server_ side.  Basically, put an old VM on the server,
> and push data to it with VM, and you get something like a steady
> 16.5MB/s.  Put a new VM in and you get pulsed behaviour.  Maybe 18.5MB/s
> tops, dropping to nothing, then picking up again, at maybe 7s intervals.

I'll just let you know (in secret) one of the graphs that Arne sent me
today ...

  http://web.kip.uni-heidelberg.de/~wiebalck/results/plots/disk_net_GbE.pdf

I don't know the details of this experiment, but it's a push of data
over the Giga-net through ENBD to a server with a modern VM. I think
the timing on the server graph is slightly shifted .. I believe it's
been shown in other experiments that the server disk i/o blocks first,
and then the network backs up afterwards.

Peter