On Thu, Jun 02, 2011 at 11:40:26AM +0930, Rusty Russell wrote: > On Wed, 1 Jun 2011 12:49:54 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > In the (rare) case where new descriptors are used > > while virtio_net enables vq callback for the TX vq, > > virtio_net uses the number of sg entries in the skb it frees to > > calculate how many descriptors in the ring have just been made > > available. But this value is an overestimate: with indirect buffers > > each skb only uses one descriptor entry, meaning we may wake the queue > > only to find we still can't transmit anything. > > This is a bit misleading. > > The value is an overestimate, but so is the requirement for > 2+MAX_SKB_FRAGS, *unless* we suddenly drop into direct mode due to OOM. > > Thanks, > Rusty. I agree, it's unlikely. s/still can't transmit anything/are still out of space and need to stop the ring almost at once/ Better? -- 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
