netdev - Re: [PATCH net-next v3 4/4] net: vhost: add rx busy polling in tx path

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Date:   Sat, 30 Jun 2018 16:48:20 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     brouer@...hat.com
Cc:     jasowang@...hat.com, mst@...hat.com, makita.toshiaki@....ntt.co.jp,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Tonghao Zhang <zhangtonghao@...ichuxing.com>
Subject: Re: [PATCH net-next v3 4/4] net: vhost: add rx busy polling in tx path

On Sat, Jun 30, 2018 at 3:03 PM Jesper Dangaard Brouer
<brouer@...hat.com> wrote:
>
> On Fri, 29 Jun 2018 23:33:58 -0700
> xiangxia.m.yue@...il.com wrote:
>
> > From: Tonghao Zhang <xiangxia.m.yue@...il.com>
> >
> > This patch improves the guest receive and transmit performance.
> > On the handle_tx side, we poll the sock receive queue at the
> > same time. handle_rx do that in the same way.
> >
> > We set the poll-us=100us and use the iperf3 to test
>
> Where/how do you configure poll-us=100us ?
>
> Are you talking about /proc/sys/net/core/busy_poll ?
No, we set the poll-us in qemu. e.g
-netdev tap,ifname=tap0,id=hostnet0,vhost=on,script=no,downscript=no,poll-us=100

>
> p.s. Nice performance boost! :-)
>
> > its bandwidth, use the netperf to test throughput and mean
> > latency. When running the tests, the vhost-net kthread of
> > that VM, is alway 100% CPU. The commands are shown as below.
> >
> > iperf3  -s -D
> > iperf3  -c IP -i 1 -P 1 -t 20 -M 1400
> >
> > or
> > netserver
> > netperf -H IP -t TCP_RR -l 20 -- -O "THROUGHPUT,MEAN_LATENCY"
> >
> > host -> guest:
> > iperf3:
> > * With the patch:     27.0 Gbits/sec
> > * Without the patch:  14.4 Gbits/sec
> >
> > netperf (TCP_RR):
> > * With the patch:     48039.56 trans/s, 20.64us mean latency
> > * Without the patch:  46027.07 trans/s, 21.58us mean latency
> >
> > This patch also improves the guest transmit performance.
> >
> > guest -> host:
> > iperf3:
> > * With the patch:     27.2 Gbits/sec
> > * Without the patch:  24.4 Gbits/sec
> >
> > netperf (TCP_RR):
> > * With the patch:     47963.25 trans/s, 20.71us mean latency
> > * Without the patch:  45796.70 trans/s, 21.68us mean latency
> >
> > Signed-off-by: Tonghao Zhang <zhangtonghao@...ichuxing.com>
>
> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer