Messages in this thread | | | Date | Mon, 5 Apr 2010 15:17:20 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] VMware Balloon driver |
| |
On Mon, 05 Apr 2010 15:03:08 -0700 Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> On 04/05/2010 02:24 PM, Andrew Morton wrote: > > I think I've forgotten what balloon drivers do. Are they as nasty a > > hack as I remember believing them to be? > > > > (I haven't looked at Dmitry's patch yet, so this is from the Xen > perspective.) > > In the simplest form, they just look like a driver which allocates a > pile of pages, and the underlying memory gets returned to the > hypervisor. When you want the memory back, it reattaches memory to the > pageframes and releases the memory back to the kernel. This allows a > virtual machine to shrink with respect to its original size. > > Going the other way - expanding beyond the memory allocation - is a bit > trickier because you need to get some new page structures from > somewhere. We don't do this in Xen yet, but I've done some experiments > with hotplug memory to implement this. Or a simpler approach is to fake > up some reserved E820 ranges to grow into. >
Lots of stuff for Dmitry to add to his changelog ;)
> > A summary of what this code sets out to do, and how it does it would be > > useful. > > > > Also please explain the applicability of this driver. Will xen use it? > > kvm? Out-of-tree code? > > > The basic idea of the driver is to allow a guest system to give up > memory it isn't using so it can be reused by other virtual machines (or > the host itself).
So... does this differ in any fundamental way from what hibernation does, via shrink_all_memory()?
| |