Re: xen affinity in an SMP system

[Paul Dorman <pauld@cwa.co.nz>]

On Monday 11 October 2004 10:01 pm, Keir Fraser wrote:
> > > As I understand it, a domain is tied to a specific CPU on startup, and
> > > if it can be changed, it can only be changed manually. Is that right?
> >
> > Yup, it's changed manually using an xm command (probably "xm pincpu [dom]
> > [cpu]" but I've never used it and could be wrong ;-).
>
> Yes, that works.
>
> > > Is it possible to have xen (or xend) check at regular intervals and
> > > move a domain to another physical CPU depending on current load?
> >
> > Currently this isn't done but it's perfectly feasible.  Sensible options
> > are: 1) Have an scheduler in Xen that will migrate domains about at run
> > time. 2) Have the load balancer task in Xend.
>
> Alternatively you could do it with a small external program. This
> would poll either xend to get load stats for each domain, or could use
> libxc directly. It would then talk to xend to re-pin appropriate
> domains.
>
> A nice simple modular piece of functionality that would be easy to
> maintain and modify.

This is the approach I like for sure. It's much easier for someone like me 
(who isn't a low-level systems programmer) to write scripts to do this sort 
of stuff. I think you'll get much more community input this way too, and it 
doesn't negate the possibility of building load-balancing capabilities in at 
a later date.

I intend to use a combination of tools on the VMs themselves, reporting back 
to a central control script, and whatever auxilliary information I can get 
from Xen and dom-0's proc.

Paul


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