Re: [Xen-devel] out-of-memory problem when restoringballooneddomains

[Kip Macy <kip.macy@xxxxxxxxx>]

If it doesn't work already it is a neccessity long term to leverage
Xen for zero downtime upgrades.  Otherwise you end up having to leave
spare capacity available to ensure that a guest can be migrated.


           -Kip


On 5/4/05, Lars Rasmusson <Lars.Rasmusson@xxxxxx> wrote:
> 
> Hi, about two months ago I inquired about if xen could restore (or
> migrate) a *ballooned* domain if its unballoned size won't fit.
> 
> Example: on a 2G machine
> 
>   xm create domain1 memory=1500
>   xm balloon domain1 128
>   xm save domain1 saved1
> 
>   xm create domain2 memory=1500
> 
>   xm restore saved1
>   *** BEEP! Xen refuses ***
> 
> Is there any news on this issue?
> 
> I think this would be a very useful feature to have.
> 
> Even better would be if one could boot a machine giving it the impression
> pf having the whole memory space but without actually ever giving it all
> of memory, something like
> 
>   xm create domain1 memory=1500 balloon=128
> 
> if you see what I mean.
> 
> Anyway, thanks for all the cool stuff you're doing!
> 
> /Lars
> 
> 
> On Fri, 11 Mar 2005, Keir Fraser wrote:
> 
> >
> > On 10 Mar 2005, at 23:35, Lars Rasmusson wrote:
> >
> > > I think the relevant part from the log is this.
> > >
> > > xc_linux_restore start
> > > Could not create domain. pfns=460800, 1843200KB
> > > Could not create domain. pfns=460800, 1843200KB
> > > 4526 [INF] XFRD> Xfr service err=1
> >
> > Ah! The problem is that we initially create the domain with its
> > 'maximum possible' memory allocation, and then automatically 'balloon
> > it down' at the end of the restore operation. Of course by the third
> > domain you do not have 1.8GB of headroom and so the third restore
> > fails.
> >
> > This probably made live relocation easier to implement, but we need to
> > change this to allocate only the memory that the domain is currently
> > using during each round of pre-copy migration. Getting non-live moved
> > over is the first step, and then fix live relocation, I guess.
> >
> >   -- Keir
> >
> >
> >
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