RE: [Xen-devel] RE: Ballooning up

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> From: Jeremy Fitzhardinge [mailto:jeremy@xxxxxxxx]
> Sent: Wednesday, September 15, 2010 11:29 AM
> To: Ian Campbell
> Cc: Dan Magenheimer; Stefano Stabellini; Xen-devel@xxxxxxxxxxxxxxxxxxx;
> Daniel Kiper; Konrad Wilk
> Subject: Re: [Xen-devel] RE: Ballooning up
> 
>  On 09/15/2010 12:10 AM, Ian Campbell wrote:
> >> Indeed.  I think adding general 32x limit between base and max size
> will
> >> prevent a completely unusable system, and then just suggest using
> mem=
> >> to control that more precisely (esp for dom0).
> > Sounds reasonable.
> 
> I found 32x doesn't work; there seems to be a lot more per-page
> overhead
> than I expected.  I made the limit 10x, which I determined empirically
> and somewhat arbitrarily, but it does seem reasonable.

Any idea what amount/percent of memory is "wasted" with this limit?
(e.g. assuming a system with 10GB physical memory and dom0_mem=1G
and no up-ballooning)

So if one knows a priori that dom0 will not be ballooned up
above dom0_mem, one specifies dom0_mem= on the xen boot line
and mem= on the dom0 "module" line?

IIRC the Linux mem=1G option doesn't really limit physical
memory to 1G, just specifies the highest legal address, ignoring
holes.  Dunno if dom0_mem has this problem (on xenolinux)
but I think it does not.

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