linux-kernel - Re: [PATCH] vhost: Add polling mode

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Date:	Sun, 17 Aug 2014 15:35:39 +0300
From:	Razya Ladelsky <RAZYA@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	abel.gordon@...il.com, Alex Glikson <GLIKSON@...ibm.com>,
	David Miller <davem@...emloft.net>,
	Eran Raichstein <ERANRA@...ibm.com>,
	Joel Nider <JOELN@...ibm.com>, kvm@...r.kernel.org,
	kvm-owner@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	Yossi Kuperman1 <YOSSIKU@...ibm.com>
Subject: Re: [PATCH] vhost: Add polling mode

> > 
> > Hi Michael,
> > 
> > Sorry for the delay, had some problems with my mailbox, and I realized 

> > just now that 
> > my reply wasn't sent.
> > The vm indeed ALWAYS utilized 100% cpu, whether polling was enabled or 

> > not.
> > The vhost thread utilized less than 100% (of the other cpu) when 
polling 
> > was disabled.
> > Enabling polling increased its utilization to 100% (in which case both 

> > cpus were 100% utilized). 
> 
> Hmm this means the testing wasn't successful then, as you said:
> 
>    The idea was to get it 100% loaded, so we can see that the polling is
>    getting it to produce higher throughput.
> 
> in fact here you are producing more throughput but spending more power
> to produce it, which can have any number of explanations besides polling
> improving the efficiency. For example, increasing system load might
> disable host power management.
>

Hi Michael,
I re-ran the tests, this time with the  "turbo mode" and  "C-states" 
features off.
No Polling:
1 VM running netperf (msg size 64B): 1107 Mbits/sec
 Polling:
1 VM running netperf (msg size 64B): 1572 Mbits/sec








As you can see from the new results, the numbers are lower, 
but relatively (polling on/off) there's no change.
Thank you,
Razya


 


 
> 
> > > -- 
> > > MST
> > > 
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