Xen devel - Apr 2013 - Re: [libvirt] [PATCH RESENT 04/12] libxl: populate xenstore memory entries at startup

On Thu, 2013-04-11 at 05:09 +0100, Jim Fehlig wrote:
> > +    /* This will fill xenstore info about free and dom0 memory - if
missing,
> > +     * should be called before starting first domain */
> > +    if (libxl_get_free_memory(libxl_driver->ctx, &free_mem)) {
> > +        VIR_ERROR(_("cannot get free memory info"));
> > +        goto error;
> > +    }
> >   
> 
> Should failure of libxl_get_free_memory() really be fatal and prevent
> the driver from loading?
I''m not sure it is intended to be called like this...

I think it is intended to be called as part of starting every domain, to
check if there is enough free memory for that domain, rather than
calling it once at start of day.

In that context if it fails or returns less than the required amount of
memory then that would be fatal for starting that domain.

In xl we use this as part of the auto balloon of dom0, see
xl_cmdimplg.c:freemem. Does libvirt do autoballooning or does it require
dom0_mem? Perhaps this is handled at a higher level?

Ian.


> 
> Regards,
> Jim
> 
> > +
> >      if (!(libxl_driver->xmlconf =
virDomainXMLConfNew(&libxlDomainXMLPrivateDataCallbacks,
> >                                                        NULL)))
> >          goto error;
> >   
> 
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