[Xen-ia64-devel] Re: [Xen-devel] [PATCH] Fix auto-ballooning of dom0 for HVM domains

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 22 May 2006, at 16:38, Keir Fraser wrote:

> > Unless, of course, the HVM domain has eaten up some of the slack in 
> > the
> > mean-time, in which case dom0 frees up PV-guest-size minus
> > remaining-slack.
> The auto-ballooning logic is shagged then. xend should keep track of 
> memory requirements (inc. max overheads) of every domain, then ensure 
> dom0 memory usage is no greater than total memory minus sum of all 
> other domains' memory requirements. How hard can that be? (Too hard 
> for original author I guess ;-) ).
> Anyway, I'm going to back out the "4MB slack" hack. Auto-ballooning 
> can never be stable in its current form (consider a guest that 
> temporarily balloons down from 128MB to 64MB, then another (HVM) guest 
> starts, then it tries to balloon back to 128MB -- it'll fail, and the 
> HVM guest will lose any headroom it required).
Actually, since there is an argument for keeping it for live migration, 
I'll keep it for the time being. But it does sound like auto-ballooning 
needs some more thought.
I'll apply a suitable patch for ia64 shortly....

 -- Keir


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