On Tue, Jul 17, 2012 at 03:02:45PM +0200, Paolo Bonzini wrote: > Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: > > On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: > >> On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > >>>> Knowing the answer to that is important before anyone can say whether > >>>> this approach is good or not. > >>>> > >>>> Stefan > >>> > >>> Why is it? > >> > >> Because there might be a fix to kvmtool which closes the gap. It > >> would be embarassing if vhost-blk was pushed just because no one > >> looked into what is actually going on. > > > > Embarrasing to whom? Is someone working on an optimization that > > makes the work in question redundant, with posting just around > > the corner? Then maybe the thing to do is just wait a bit. > > Of course there is work going on to make QEMU perform better. > Not sure about lkvm. > > >> And on the flipside, hard evidence of an overhead that cannot be > >> resolved could be good reason to do more vhost devices in the future. > > > > How can one have hard evidence of an overhead that cannot be resolved? > > Since we do have two completely independent userspaces (lkvm and > data-plane QEMU), you can build up some compelling evidence of an > overhead that cannot be resolved in user space. OK, so what you are saying benchmark against data-plane QEMU? I agree actually. Asias, any data? > >> Either way, it's useful to do this before going further. > > > > I think each work should be discussed on its own merits. Maybe > > vhost-blk is just well written. So? What is your conclusion? > > If it's just that vhost-blk is written well, my conclusion is that lkvm > people should look into improving their virtio-blk userspace. We take > hints from each other all the time, for example virtio-scsi will have > unlocked kick in 3.6. > > Why can't vhost-* just get into staging, and we call it a day? > > Paolo staging is not a destination. Even if we put a driver in staging it won't stay there indefinitely if qemu-kvm is not using it, something that doesn't seem to be addressed for vhost-blk yet. -- MST -- 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
