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author? jiang <jiangkidd@hotmail.com>2019-08-20 02:51:23 +0000
committerMichael S. Tsirkin <mst@redhat.com>2019-09-04 06:21:17 -0400
commit718be6bab26fb01fa0147a2b614a3eefd96a2957 (patch)
tree1b11a31a2ef6a4afede5b6fe723ebe00b5670ab5
parent264b563b8675771834419057cbe076c1a41fb666 (diff)
virtio-net: lower min ring num_free for efficiency
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@hotmail.com> Acked-by: Jason Wang <jasowang@redhat.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
-rw-r--r--drivers/net/virtio_net.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4f3de0ac8b0b..ba98e0971b84 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);
}