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Re: [Xen-devel] xen affinity in an SMP system

To: mark.williamson@xxxxxxxxxxxx
Subject: Re: [Xen-devel] xen affinity in an SMP system
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 11 Oct 2004 10:01:18 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxxx, "James Harper" <JamesH@xxxxxxxxxxxxxxxx>
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> > 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.

 -- Keir


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