On Wed, Jun 27, 2012 at 08:48:55AM -0700, Frank Swiderski wrote: > On Tue, Jun 26, 2012 at 7:56 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote: > > On Wed, 27 Jun 2012 00:41:06 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > >> On Tue, Jun 26, 2012 at 01:32:58PM -0700, Frank Swiderski wrote: > >> > This implementation of a virtio balloon driver uses the page cache to > >> > "store" pages that have been released to the host. The communication > >> > (outside of target counts) is one way--the guest notifies the host when > >> > it adds a page to the page cache, allowing the host to madvise(2) with > >> > MADV_DONTNEED. Reclaim in the guest is therefore automatic and implicit > >> > (via the regular page reclaim). This means that inflating the balloon > >> > is similar to the existing balloon mechanism, but the deflate is > >> > different--it re-uses existing Linux kernel functionality to > >> > automatically reclaim. > >> > > >> > Signed-off-by: Frank Swiderski <fes@xxxxxxxxxx> > >> > >> I'm pondering this: > >> > >> Should it really be a separate driver/device ID? > >> If it behaves the same from host POV, maybe it > >> should be up to the guest how to inflate/deflate > >> the balloon internally? > > > > Well, it shouldn't steal ID 10, either way :) Either use a completely > > bogus number, or ask for an id. > > > > But AFAICT this should be a an alternate driver of for the same device: > > it's not really a separate device, is it? > > > > Cheers, > > Rusty. > > Apologies, Rusty. Asking for an ID is in the virtio spec, and I > completely neglected that step. Though as you and others have pointed > out, this probably fits better as a different driver for the same > device. Since it changes whether or not the deflate operation is > necessary, it also seems that how this should look is different > behavior based on a feature bit in the device. > > If that sounds reasonable, then what I'll do with this patch is merge > it with the existing virtio balloon driver with a feature bit for > determining which behavior to use. > > I also think the idea of a generic balloon that the different balloon > drivers use for the inflate/deflate operations is interesting and > useful, though I think the suggestion of pending that until later is > correct. > > Sounds reasonable? > > Regards, > fes I think a spec patch would be a good spec at this point. You can get the spec from Rusty, or a mirror from my git: git://git.kernel.org/pub/scm/virt/kvm/mst/virtio-spec.git -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
