On 24 February 2014 16:20, Stefan Hajnoczi <stefa...@gmail.com> wrote:
> On Fri, Feb 14, 2014 at 02:43:14PM +0100, Luke Gorrie wrote: > > In Snabb Switch we are creating a 1:1 mapping between Virtio-net > > descriptors and VMDq hardware receive descriptors. The VMDq queues > support > > 32768 buffers and I'd like to match this on the QEMU/Virtio-net side -- > or > > at least come close. > [...] > Do you want the 1:1 mapping to achieve best performance or just to > simplify the coding? > More background: The 1:1 mapping between hardware RX descriptors and Virtio-net descriptors is for best performance, specifically for zero-copy operation. We want the NIC to DMA the packets directly into guest memory and that's why we need to pre-populate the NIC descriptor lists with suitable memory obtained from the guest via the Virtio-net avail ring.
