From 718be6bab26fb01fa0147a2b614a3eefd96a2957 Mon Sep 17 00:00:00 2001 From: ? jiang Date: Tue, 20 Aug 2019 02:51:23 +0000 Subject: [PATCH] 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 Acked-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- 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 4f3de0a..ba98e09 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); } -- 2.7.4