Re: [PATCH] enforce dom0 cpus and balloon out memory

[Ryan Harper <ryanh@us.ibm.com>]

* Mark Williamson <mark.williamson@cl.cam.ac.uk> [2005-07-29 10:25]:
> > You could use vcpu-hotplug to drop the extra cpus from dom0 instead of
> > writing directly into sysfs.  The only stopper to that approach is the
> > fact that dom0's self.channel is not initialized when xend starts and
> > subsequently doesn't send the control message.  Channels are initialized
> > when a domain is built, but since dom0 is built by xen, the routine
> > which sets up channels isn't called for dom0.  Haven't found a good place
> > for xend to initialized the channel for dom0 yet either.
> 
> Hmmm.  Is the channel never set up then?  It'd certainly be nice if it were: 

Correct.  As mentioned above, this is only a problem for dom0 since the
xend contruct_image() code isn't called for dom0 as xen is the builder.
The fix is as simple as calling create_channel() from dom0's XendDomInfo
object.  I've not determined the appropriate location to issue the call.

> then you can use "xm balloon" to set dom0's memory footprint, which is 
> preferable to using the /proc interface directly.

Indeed.  Same goes for using vcpu_hotplug() versus sysfs

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
ryanh@us.ibm.com