On Thu, Apr 02, 2009 at 10:43:19PM +1030, Rusty Russell wrote: > On Thursday 02 April 2009 21:36:07 Gregory Haskins wrote: > > You do not need to know when the packet is copied (which I currently > > do). You only need it for zero-copy (of which I would like to support, > > but as I understand it there are problems with the reliability of proper > > callback (i.e. skb->destructor). > > But if you have a UP guest, there will *never* be another packet in the queue > at this point, since it wasn't running. > > As Avi said, you can do the processing in another thread and go back to the > guest; lguest pre-virtio did a hacky "weak" wakeup to ensure the guest ran > again before the thread did for exactly this kind of reason. > > While Avi's point about a "powerful enough userspace API" is probably valid, > I don't think it's going to happen. It's almost certainly less code to put a > virtio_net server in the kernel, than it is to create such a powerful > interface (see vringfd & tap). And that interface would have one user in > practice. > > So, let's roll out a kernel virtio_net server. Anyone? > Rusty. BTW, whatever approach is chosen, to enable zero-copy transmits, it seems that we still must add tracking of when the skb has actually been transmitted, right? Rusty, I think this is what you did in your patch from 2008 to add destructor for skb data ( http://kerneltrap.org/mailarchive/linux-netdev/2008/4/18/1464944 ): and it seems that it would make zero-copy possible - or was there some problem with that approach? Do you happen to remember? -- 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
