Re: [Xen-users] CPU intensive VM starves IO intensive VMs

[Emmanuel Ackaouy <ack@xxxxxxxxxxxxx>]

On Tue, Aug 29, 2006 at 01:31:33PM -0400, Tim Wood wrote:
> I am aware that the next version of Xen uses the new credit scheduler
> - does anyone know if that scheduler tries to deal with these kinds of
> issues?  The changes I had heard mostly regarded better supporting
> SMP.

Yeah the credit scheduler tries to enforce some fairness
between I/O intensive and CPU bound VMs. The I/O VM should
end up preempting the CPU bound one as long as it doesn't
hog the CPU itself. It should maintain good network throughput
even competing against the spinner. This is another important
attribute of the credit scheduler in addition to SMP load
balancing.

I haven't tried Iperf but have ran similar scenarios with
ttcp on the credit scheduler and have had good results.

There's also been some work done to improve performance in
the netfront/netback drivers recently in xen-unstable. I'd
be interested to know how moving to tip unstable affects
your tests. I suspect it will help a lot.

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