On Tue, Feb 11, 2014 at 10:58:52PM +0800, Qin Chuanyu wrote: > udp packet use 2 buffers at least, one for vnet_hdr and > one for skb->data.
Not really, we use 1 buffer now with vnet_hdr inline with data. > we could change the threshold from 2 to 3, so the udp packet > which data buff only using single desc will gain from this. > the guest would avoid from allocating memory dynamically. > the host would avoid from translating indirect desc. > > Signed-off-by: Chuanyu Qin <[email protected]> Optimization patch without any performance data? Such a change would need much more testing than that: would have to try various workloads with -net and -blk at least. > --- > drivers/virtio/virtio_ring.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 28b5338..88d008f 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -220,7 +220,7 @@ static inline int virtqueue_add(struct virtqueue *_vq, > > /* If the host supports indirect descriptor tables, and we have multiple > * buffers, then go indirect. FIXME: tune this threshold */ > - if (vq->indirect && total_sg > 1 && vq->vq.num_free) { > + if (vq->indirect && total_sg > 2 && vq->vq.num_free) { > head = vring_add_indirect(vq, sgs, next, total_sg, total_out, > total_in, > out_sgs, in_sgs, gfp); > -- > 1.7.3.1.msysgit.0 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
