Re: [Xen-devel] unstable: no ballooning

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

On Fri, Oct 14, 2005 at 10:40:17AM +0200, Kurt Garloff wrote:

> > The idea is that the memory/target value gets written by Xend, and and the
> > balloon driver holds a watch on that value in the store.  When the watch
> > fires, the balloon driver should respond by setting the new target
> > (drivers/xen/balloon/balloon.c:watch_target).
> 
> The kernel watches data from a userspace file?
> So the kernel understands the tdb/xenstore format?
> I wonder whether that's the cleanest way to implement this feature.

It's not a userspace file, as such, but a daemon running in domain 0.  The
daemon isolates domains from the tdb format, exposing a filesystem-style
heirarchical namespace, and maintaining transaction semantics, firing callbacks
when portions of the namespace change, and maintaining an implicit root for
each connection.  It is not necessary for drivers such as the balloon driver
to understand the exact layout of the store, but they do need to know how to
contact the store and the path from the domain's implicit root to the details
in which they are interested.  All changes in domain configuration and state
are handled in this way.

Ewan.

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