Michael S. Tsirkin
2019-Sep-02 15:01 UTC
[PATCH v3] virtio-net: lower min ring num_free for efficiency
On Tue, Aug 20, 2019 at 02:51:23AM +0000, ? jiang wrote:> This change lowers ring buffer reclaim threshold from 1/2*queue to budget > for better performance. According to our test with qemu + dpdk, packet > dropping happens when the guest is not able to provide free buffer in > avail ring timely with default 1/2*queue. The value in the patch has been > tested and does show better performance. > > Test setup: iperf3 to generate packets to guest (total 30mins, pps 400k, UDP) > avg packets drop before: 2842 > avg packets drop after: 360(-87.3%) > > Further, current code suffers from a starvation problem: the amount of > work done by try_fill_recv is not bounded by the budget parameter, thus > (with large queues) once in a while userspace gets blocked for a long > time while queue is being refilled. Trigger refills earlier to make sure > the amount of work to do is limited. > > Signed-off-by: jiangkidd <jiangkidd at hotmail.com> > Acked-by: Jason Wang <jasowang at redhat.com> > Acked-by: Michael S. Tsirkin <mst at redhat.com>Dave, could you merge this please? Either net or net-next at your discretion.> --- > drivers/net/virtio_net.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 0d4115c9e20b..bc08be7925eb 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -1331,7 +1331,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget, > } > } > > - if (rq->vq->num_free > virtqueue_get_vring_size(rq->vq) / 2) { > + if (rq->vq->num_free > min((unsigned int)budget, virtqueue_get_vring_size(rq->vq)) / 2) { > if (!try_fill_recv(vi, rq, GFP_ATOMIC)) > schedule_delayed_work(&vi->refill, 0); > } > -- > 2.11.0