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

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Date:   Thu, 28 Jun 2018 12:40:10 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     xiangxia.m.yue@...il.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        Tonghao Zhang <zhangtonghao@...ichuxing.com>
Subject: Re: [PATCH net-next v2] net: vhost: improve performance when enable
 busyloop



On 2018年06月27日 23:58, Michael S. Tsirkin wrote:
> On Wed, Jun 27, 2018 at 10:24:43PM +0800, Jason Wang wrote:
>>
>> On 2018年06月26日 13:17, xiangxia.m.yue@...il.com wrote:
>>> From: Tonghao Zhang <xiangxia.m.yue@...il.com>
>>>
>>> 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 <zhangtonghao@...ichuxing.com>
>> 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.
>

I believe we had an ioctl for setting timeout? Or you want another kind 
of controlling.

Thanks