Re: how to optimize virtio-vhost in 10G net

[Jason Wang]

On Sun, Feb 15, 2015 at 3:30 PM, Ding Xiao <ssdxiaoding@xxxxxxxxx> 
wrote:
> I am test virtio-vhost in 10G environment
>
> host info
> cpu E2680@xxxxxx
> memory 16G
> network intel 82599BE
> os centos 7
>
> VM info
> cpu 4
> memory 4G
> network using virtio vhost
> os centos 7
>
> I using pktgen to send udp package, the result like follow
> 64b 230Mb/s
> 1400b 5.9Gb/s
>
> I test the speed in VMware too, the result like follow
> 64b 700Mb/s
> 1400 9.3Gb/s
>
> I am very surprised why the speed with virtio-vhost is slow
> so I test to analysis this by using perf tool
> I found the tun_sendmsg occupancy rate of 35%

It looks like you're using pktgen in guest. Pktgen has known issue with 
driver that does not have tx completion. See discussion here: 
https://patchwork.kernel.org/patch/1800711/

So you can't trust pktgen result in this case.
> tun_sendmsg using copy_from_user to get the data from VM
> Perhaps mapping could improve the performance ?

If you enable vhost_net zerocopy, you will see obvious improvements.
> or other Another improvement method ?

I suggest that you can use other benchmark tools (or apply the patch in 
the above link with pktgen).
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/