On Sun, 15 May 2011 16:55:41 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > On Mon, May 09, 2011 at 02:03:26PM +0930, Rusty Russell wrote: > > On Wed, 4 May 2011 23:51:47 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > Use the new avail_event feature to reduce the number > > > of exits from the guest. > > > > Figures here would be nice :) > > You mean ASCII art in comments? I mean benchmarks of some kind. > > > > @@ -228,6 +237,12 @@ add_head: > > > * new available array entries. */ > > > virtio_wmb(); > > > vq->vring.avail->idx++; > > > + /* If the driver never bothers to kick in a very long while, > > > + * avail index might wrap around. If that happens, invalidate > > > + * kicked_avail index we stored. TODO: make sure all drivers > > > + * kick at least once in 2^16 and remove this. */ > > > + if (unlikely(vq->vring.avail->idx == vq->kicked_avail)) > > > + vq->kicked_avail_valid = true; > > > > If they don't, they're already buggy. Simply do: > > WARN_ON(vq->vring.avail->idx == vq->kicked_avail); > > Hmm, but does it say that somewhere? AFAICT it's a corollary of: 1) You have a finite ring of size <= 2^16. 2) You need to kick the other side once you've done some work. > > > @@ -482,6 +517,8 @@ void vring_transport_features(struct virtio_device *vdev) > > > break; > > > case VIRTIO_RING_F_USED_EVENT_IDX: > > > break; > > > + case VIRTIO_RING_F_AVAIL_EVENT_IDX: > > > + break; > > > default: > > > /* We don't understand this bit. */ > > > clear_bit(i, vdev->features); > > > > Does this belong in a prior patch? > > > > Thanks, > > Rusty. > > Well if we don't support the feature in the ring we should not > ack the feature, right? Ah, you're right. Thanks, Rusty. -- 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
