On Thu, Jan 27, 2011 at 11:45:47AM -0800, Shirley Ma wrote: > On Thu, 2011-01-27 at 21:31 +0200, Michael S. Tsirkin wrote: > > Well slowing down the guest does not sound hard - for example we can > > request guest notifications, or send extra interrupts :) > > A slightly more sophisticated thing to try is to > > poll the vq a bit more aggressively. > > For example if we handled some requests and now tx vq is empty, > > reschedule and yeild. Worth a try? > > I used dropping packets in high level to slow down TX. > I am still > thinking what's the right the approach here. Interesting. Could this is be a variant of the now famuous bufferbloat then? I guess we could drop some packets if we see we are not keeping up. For example if we see that the ring is > X% full, we could quickly complete Y% without transmitting packets on. Or maybe we should drop some bytes not packets. > > Requesting guest notification and extra interrupts is what we want to > avoid to reduce VM exits for saving CPUs. I don't think it's good. Yes but how do you explain regression? One simple theory is that guest net stack became faster and so the host can't keep up. > > By polling the vq a bit more aggressively, you meant vhost, right? > > Shirley Yes. -- 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
