Re: [Xen-devel] How much memory does a domain REALLY use...

[nick@xxxxxxxxxxxxxx (Nick Craig-Wood)]

Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:
>  On 24/2/07 19:14, "Graham, Simon" <Simon.Graham@xxxxxxxxxxx> wrote:
> 
> > Hmm - it does indeed seem to be somewhat dependent on the size of the
> > machine; I have a bunch of systems from 2GB to 16GB all of which are
> > running a 768MB Dom0 currently; here's what I see for used memory
> > (total/free as reported by xenstat) for some of these when just Dom0 is
> > running:
> > 
> > . 2GB system; 794MB used
> > . 6GB system; 830MB used
> > . 8GB system; 840MB used
> > . 16GB system; 890MB used
> 
>  Yes, there's an overhead of 7MB per 1GB on i386, and 12MB per 1GB
>  on x86/64.

Some time ago (xen 3.0.2 I think) I measured the overhead on i386 to be

  12 MB per domain
  plus 6MB per GB host RAM

I guess it has gone up since the above figures fit the 7MB amount much
better

>>> for total in (2, 6, 8, 16): print "Total",total,"Calculated 
>>> used",total*7+12+768
... 
Total 2 Calculated used 794
Total 6 Calculated used 822
Total 8 Calculated used 836
Total 16 Calculated used 892

-- 
Nick Craig-Wood <nick@xxxxxxxxxxxxxx> -- http://www.craig-wood.com/nick

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