Re: [libvirt] [PATCH] allow memballoon type of none to desactivate it

On Mon, Aug 09, 2010 at 06:53:34PM +0100, Daniel P. Berrange wrote: > On Mon, Aug 09, 2010 at 06:38:27PM +0200, Daniel Veillard wrote: > > The balloon device is automatically added to qemu guests if supported, > > but it may be useful to desactivate it. The simplest to not change the > > existing behaviour is to allow > > <memballoon type="none"/> > > as an extra option to desactivate it (it is automatically added if the > > memballoon construct is missing for the domain). > > The following simple patch just adds the extra option and does not > > change the default behaviour but avoid creating a balloon device if > > type="none" is used. > > I really don't like the idea of 'type=none' devices in general. Since we automagically add the devices to describe an internal policy I think we're at fault here. > I don't think we should have an element insides <devices> that > doesn't actually represent a device. > > If we want to disable the balloon, then I think we should aim > for an element or attribute elsewhere to toggle it. > > eg, perhaps the earlier <memory> element can indicate whether it > supports ballooning. eg > > <memory ballonable='yes|no'>2423423432</memory> > > Thus if ballooning is not enabled, the <memballoon> device would > never need to appear within <devices> Grumpf ... that mean at the internal stucture level we need to add an extra field, that is detected at a completely different time in parsing too ... more complex in general, but I can understand the purity POV.