netdev - Re: 8% performance improved by change tap interact with kernel stack

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Date:	Tue, 28 Jan 2014 08:56:34 -0800
From:	Rick Jones <rick.jones2@...com>
To:	Qin Chuanyu <qinchuanyu@...wei.com>,
	"Michael S. Tsirkin" <mst@...hat.com>
CC:	jasowang@...hat.com, Anthony Liguori <anthony@...emonkey.ws>,
	KVM list <kvm@...r.kernel.org>, netdev@...r.kernel.org
Subject: Re: 8% performance improved by change tap interact with kernel stack

On 01/28/2014 01:14 AM, Qin Chuanyu wrote:
> On 2014/1/28 16:34, Michael S. Tsirkin wrote:
>> Could you please check latency results?
>>
> netperf UDP_RR 512
> test model: VM->host->host
>
> modified before : 11108
> modified after  : 11480
>
> 3% gained by this patch

Netperf UDP_RR can be very sensitive to packet losses.  Not that there 
were necessarily any in your tests, but to further confirm the 3% 
improvement in latency, I would suggest using the confidence intervals 
functionality in your before/after netperf testing.  And to get at what 
Michael asks about CPU utilization I would suggest:

netperf -H <otherguy> -c -C -l 30 -i 30,3 -t UDP_RR -- -r 512

(I was guessing as to what netperf options you may have been using already)

happy benchmarking,

rick jones

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