On Wed, Oct 08, 2014 at 12:51:21PM +0300, Avi Kivity wrote: > > On 10/08/2014 12:15 PM, Michael S. Tsirkin wrote: > >On Wed, Oct 08, 2014 at 10:43:07AM +0300, Avi Kivity wrote: > >>On 09/30/2014 12:33 PM, Michael S. Tsirkin wrote: > >>>a single descriptor might use all of > >>>the virtqueue. In this case we wont to be able to pass the > >>>descriptor directly to linux as a single iov, since > >>> > >>You could separate maximum request scatter/gather list size from the > >>virtqueue size. They are totally unrelated - even now you can have a larger > >>request by using indirect descriptors. > >We could add a feature to have a smaller or larger S/G length limit. > >Is this something useful? > > > > Having a larger ring size is useful, esp. with zero-copy transmit, and you > would need the sglist length limit in order to not require linearization on > linux hosts. So the limit is not useful in itself, only indirectly. > > Google cloud engine exposes virtio ring sizes of 16384.
OK this sounds useful, I'll queue this up for consideration. Thanks! > Even more useful is getting rid of the desc array and instead passing descs > inline in avail and used. You expect this to improve performance? Quite possibly but this will have to be demonstrated. -- MST
