On Tue, Apr 03, 2018 at 08:08:26AM +0000, haibinzhang(张海斌) wrote:
> handle_tx will delay rx for a long time when tx busy polling udp packets
> with small length(e.g. 1byte udp payload), because setting VHOST_NET_WEIGHT
> takes into account only sent-bytes but no single packet length.
>
> Tests were done between two Virtual Machines using netperf(UDP_STREAM, len=1),
> then another machine pinged the client. Result shows as follow:
>
> Packet# Ping-Latency(ms)
> min avg max
> Origin 3.319 18.489 57.503
> 64 1.643 2.021 2.552
> 128 1.825 2.600 3.224
> 256 1.997 2.710 4.295
> 512* 1.860 3.171 4.631
> 1024 2.002 4.173 9.056
> 2048 2.257 5.650 9.688
> 4096 2.093 8.508 15.943
>
> 512 is selected, which is multi-VRING_SIZE
There's no guarantee vring size is 256.
Could you pls try with a different tx ring size?
I suspect we want:
#define VHOST_NET_PKT_WEIGHT(vq) ((vq)->num * 2)
> and close to VHOST_NET_WEIGHT/MTU.
Puzzled by this part. Does tweaking MTU change anything?
> To evaluate this change, another tests were done using netperf(RR, TX) between
> two machines with Intel(R) Xeon(R) Gold 6133 CPU @ 2.50GHz. Result as follow
> does not show obvious changes:
>
> TCP_RR
>
> size/sessions/+thu%/+normalize%
> 1/ 1/ -7%/ -2%
> 1/ 4/ +1%/ 0%
> 1/ 8/ +1%/ -2%
> 64/ 1/ -6%/ 0%
> 64/ 4/ 0%/ +2%
> 64/ 8/ 0%/ 0%
> 256/ 1/ -3%/ -4%
> 256/ 4/ +3%/ +4%
> 256/ 8/ +2%/ 0%
>
> UDP_RR
>
> size/sessions/+thu%/+normalize%
> 1/ 1/ -5%/ +1%
> 1/ 4/ +4%/ +1%
> 1/ 8/ -1%/ -1%
> 64/ 1/ -2%/ -3%
> 64/ 4/ -5%/ -1%
> 64/ 8/ 0%/ -1%
> 256/ 1/ +7%/ +1%
> 256/ 4/ +1%/ +1%
> 256/ 8/ +2%/ +2%
>
> TCP_STREAM
>
> size/sessions/+thu%/+normalize%
> 64/ 1/ 0%/ -3%
> 64/ 4/ +3%/ -1%
> 64/ 8/ +9%/ -4%
> 256/ 1/ +1%/ -4%
> 256/ 4/ -1%/ -1%
> 256/ 8/ +7%/ +5%
> 512/ 1/ +1%/ 0%
> 512/ 4/ +1%/ -1%
> 512/ 8/ +7%/ -5%
> 1024/ 1/ 0%/ -1%
> 1024/ 4/ +3%/ 0%
> 1024/ 8/ +8%/ +5%
> 2048/ 1/ +2%/ +2%
> 2048/ 4/ +1%/ 0%
> 2048/ 8/ -2%/ 0%
> 4096/ 1/ -2%/ 0%
> 4096/ 4/ +2%/ 0%
> 4096/ 8/ +9%/ -2%
>
> Signed-off-by: Haibin Zhang <haibinzhang@xxxxxxxxxxx>
> Signed-off-by: Yunfang Tai <yunfangtai@xxxxxxxxxxx>
> Signed-off-by: Lidong Chen <lidongchen@xxxxxxxxxxx>
> ---
> drivers/vhost/net.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 8139bc70ad7d..13a23f3f3ea4 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -44,6 +44,10 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
> * Using this limit prevents one virtqueue from starving others. */
> #define VHOST_NET_WEIGHT 0x80000
>
> +/* Max number of packets transferred before requeueing the job.
> + * Using this limit prevents one virtqueue from starving rx. */
> +#define VHOST_NET_PKT_WEIGHT 512
> +
> /* MAX number of TX used buffers for outstanding zerocopy */
> #define VHOST_MAX_PEND 128
> #define VHOST_GOODCOPY_LEN 256
> @@ -473,6 +477,7 @@ static void handle_tx(struct vhost_net *net)
> struct socket *sock;
> struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
> bool zcopy, zcopy_used;
> + int sent_pkts = 0;
>
> mutex_lock(&vq->mutex);
> sock = vq->private_data;
> @@ -580,7 +585,8 @@ static void handle_tx(struct vhost_net *net)
> else
> vhost_zerocopy_signal_used(net, vq);
> vhost_net_tx_packet(net);
> - if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
> + if (unlikely(total_len >= VHOST_NET_WEIGHT) ||
> + unlikely(++sent_pkts >= VHOST_NET_PKT_WEIGHT)) {
> vhost_poll_queue(&vq->poll);
> break;
> }
> --
> 2.12.3
>
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