On Fri, Feb 14, 2014 at 02:43:14PM +0100, Luke Gorrie wrote: > Observation: virtio-net.c hard-codes the vring size to 256 buffers. > > Could this reasonably be made configurable, or would that be likely to > cause a problem? > > 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.
In reality virtio-net can use many more buffers because it has the VIRTIO_RING_F_INDIRECT_DESC feature. Each descriptor can point to a whole new descriptor table. Do you want the 1:1 mapping to achieve best performance or just to simplify the coding? Since vhost_net does many Gbit/s I doubt the ring size is a limiting factor although there are still periodic discussions about tweaking the direct vs indirect descriptor heuristic. Stefan
