* Re: [PATCH v2] virtio-net: lower min ring num_free for efficiency
[not found] <BYAPR14MB32058F4B2AD162F5421BB9B4A6AC0@BYAPR14MB3205.namprd14.prod.outlook.com>
@ 2019-08-15 9:55 ` Jason Wang
2019-08-18 7:10 ` Michael S. Tsirkin
1 sibling, 0 replies; 2+ messages in thread
From: Jason Wang @ 2019-08-15 9:55 UTC (permalink / raw)
To: ? jiang, mst
Cc: davem, ast, daniel, jakub.kicinski, hawk, john.fastabend, kafai,
songliubraving, yhs, virtualization, netdev, linux-kernel,
xdp-newbies, bpf, jiangran.jr
On 2019/8/15 下午5:42, ? 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%)
>
> Signed-off-by: jiangkidd <jiangkidd@hotmail.com>
> ---
> 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);
> }
Acked-by: Jason Wang <jasowang@redhat.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH v2] virtio-net: lower min ring num_free for efficiency
[not found] <BYAPR14MB32058F4B2AD162F5421BB9B4A6AC0@BYAPR14MB3205.namprd14.prod.outlook.com>
2019-08-15 9:55 ` [PATCH v2] virtio-net: lower min ring num_free for efficiency Jason Wang
@ 2019-08-18 7:10 ` Michael S. Tsirkin
1 sibling, 0 replies; 2+ messages in thread
From: Michael S. Tsirkin @ 2019-08-18 7:10 UTC (permalink / raw)
To: ? jiang
Cc: jasowang, davem, ast, daniel, jakub.kicinski, hawk,
john.fastabend, kafai, songliubraving, yhs, virtualization,
netdev, linux-kernel, xdp-newbies, bpf, jiangran.jr
On Thu, Aug 15, 2019 at 09:42:40AM +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%)
>
> Signed-off-by: jiangkidd <jiangkidd@hotmail.com>
To add to that:
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.
With this addition to the log:
Acked-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 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
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2019-08-15 9:55 ` [PATCH v2] virtio-net: lower min ring num_free for efficiency Jason Wang
2019-08-18 7:10 ` Michael S. Tsirkin
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