Subject: Re: [PATCH net-next RFC 2/2] vhost_net: basic polling support

From: Jason Wang <[email-masked]>
Date: Fri, 23 Oct 2015 15:14:50 +0800

On 10/23/2015 12:16 AM, Michael S. Tsirkin wrote:
> On Thu, Oct 22, 2015 at 08:46:33AM -0700, Rick Jones wrote:
>> On 10/22/2015 02:33 AM, Michael S. Tsirkin wrote:
>>> On Thu, Oct 22, 2015 at 01:27:29AM -0400, Jason Wang wrote:
>>>> This patch tries to poll for new added tx buffer for a while at the
>>>> end of tx processing. The maximum time spent on polling were limited
>>>> through a module parameter. To avoid block rx, the loop will end it
>>>> there's new other works queued on vhost so in fact socket receive
>>>> queue is also be polled.
>>>>
>>>> busyloop_timeout = 50 gives us following improvement on TCP_RR test:
>>>>
>>>> size/session/+thu%/+normalize%
>>>>     1/     1/   +5%/  -20%
>>>>     1/    50/  +17%/   +3%
>>> Is there a measureable increase in cpu utilization
>>> with busyloop_timeout = 0?
>> And since a netperf TCP_RR test is involved, be careful about what netperf
>> reports for CPU util if that increase isn't in the context of the guest OS.

Right, the cpu utilization is measured on host.

>>
>> For completeness, looking at the effect on TCP_STREAM and TCP_MAERTS,
>> aggregate _RR and even aggregate _RR/packets per second for many VMs on the
>> same system would be in order.
>>
>> happy benchmarking,
>>
>> rick jones
> Absolutely, merging a new kernel API just for a specific
> benchmark doesn't make sense.
> I'm guessing this is just an early RFC, a fuller submission
> will probably include more numbers.
>

Yes, will run more complete tests.

Thanks