Subject: Re: [PATCH net-next v2] net: vhost: improve performance when enable busyloop

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 27 Jun 2018 18:58:24 +0300

On Wed, Jun 27, 2018 at 10:24:43PM +0800, Jason Wang wrote:
> 
> 
> On 2018年06月26日 13:17, [email-masked] wrote:
> > From: Tonghao Zhang <[email-masked]>
> > 
> > This patch improves the guest receive performance from
> > host. On the handle_tx side, we poll the sock receive
> > queue at the same time. handle_rx do that in the same way.
> > 
> > For avoiding deadlock, change the code to lock the vq one
> > by one and use the VHOST_NET_VQ_XX as a subclass for
> > mutex_lock_nested. With the patch, qemu can set differently
> > the busyloop_timeout for rx or tx queue.
> > 
> > We set the poll-us=100us and use the iperf3 to test
> > its throughput. The iperf3 command is shown as below.
> > 
> > on the guest:
> > iperf3  -s -D
> > 
> > on the host:
> > iperf3  -c 192.168.1.100 -i 1 -P 10 -t 10 -M 1400
> > 
> > * With the patch:     23.1 Gbits/sec
> > * Without the patch:  12.7 Gbits/sec
> > 
> > Signed-off-by: Tonghao Zhang <[email-masked]>
> 
> Thanks a lot for the patch. Looks good generally, but please split this big
> patch into separate ones like:
> 
> patch 1: lock vqs one by one
> patch 2: replace magic number of lock annotation
> patch 3: factor out generic busy polling logic to vhost_net_busy_poll()
> patch 4: add rx busy polling in tx path.
> 
> And please cc Michael in v3.
> 
> Thanks

Pls include host CPU utilization numbers. You can get them e.g. using
vmstat. I suspect we also want the polling controllable e.g. through
an ioctl.

-- 
MST