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. >> 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 -- 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
