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

["Diwaker Gupta" <diwaker.lists@xxxxxxxxx>]

On 8/30/06, Tim Wood <twwood@xxxxxxxxx> wrote:
> > On 8/29/06, Apparao, Padmashree K <padmashree.k.apparao@xxxxxxxxx> wrote:
> > What are the number of vcpus so for each VM and what physical cpus are
> > the VMs on.  I have run similar tests and seen different results from
> > what you see.
>
> For these experiments I am working on a single CPU machine. Having
> more cpus would be nice, but I'm assuming setting the sedf CPU weights
> should be sufficient for preventing any VM or Dom0 from being starved.
Single CPU machines are typically bad for such experiments. In Xen,
the execution of any I/O intensive domain gets coupled with the
execution of Domain-0 (since any traffic necessarily needs to go
through Domain-0 first). This coupling makes scheduling inefficient,
affecting the performance.

If you have a single processor P4, try enabling HT and putting Dom-0
on a thread by itself. If you can get your hands on an SMP, that would
be the best.

HTH,
Diwaker
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