netdev - Re: [PATCH net-next 0/3] xen-netback: switch to NAPI + kthread 1:1 model

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Message-ID: <20130828090135.GC15729@zion.uk.xensource.com>
Date:	Wed, 28 Aug 2013 10:01:35 +0100
From:	Wei Liu <wei.liu2@...rix.com>
To:	<netdev@...r.kernel.org>
CC:	<xen-devel@...ts.xen.org>, <ian.campbell@...rix.com>,
	<msw@...zon.com>, <konrad.wilk@...cle.com>, <annie.li@...cle.com>,
	Wei Liu <wei.liu2@...rix.com>
Subject: Re: [PATCH net-next 0/3] xen-netback: switch to NAPI + kthread 1:1
 model

Dave, ping.

This series has been acked by maintainer. If there is no objection we
would like to see it in.

Thanks
Wei.

On Mon, Aug 26, 2013 at 12:59:36PM +0100, Wei Liu wrote:
> This series implements NAPI + kthread 1:1 model for Xen netback.
> 
> This model
>  - provides better scheduling fairness among vifs
>  - is prerequisite for implementing multiqueue for Xen network driver
> 
> The second patch has the real meat:
>  - make use of NAPI to mitigate interrupt
>  - kthreads are not bound to CPUs any more, so that we can take
>    advantage of backend scheduler and trust it to do the right thing
> 
> Benchmark is done on a Dell T3400 workstation with 4 cores, running 4
> DomUs. Netserver runs in Dom0. DomUs do netperf to Dom0 with
> following command: /root/netperf -H Dom0 -fm -l120
> 
> IRQs are distributed to 4 cores by hand in the new model, while in the
> old model vifs are automatically distributed to 4 kthreads.
> 
> * New model
> %Cpu0  :  0.5 us, 20.3 sy,  0.0 ni, 28.9 id,  0.0 wa,  0.0 hi, 24.4 si, 25.9 st
> %Cpu1  :  0.5 us, 17.8 sy,  0.0 ni, 28.8 id,  0.0 wa,  0.0 hi, 27.7 si, 25.1 st
> %Cpu2  :  0.5 us, 18.8 sy,  0.0 ni, 30.7 id,  0.0 wa,  0.0 hi, 22.9 si, 27.1 st
> %Cpu3  :  0.0 us, 20.1 sy,  0.0 ni, 30.4 id,  0.0 wa,  0.0 hi, 22.7 si, 26.8 st
> Throughputs: 2027.89 2025.95 2018.57 2016.23 aggregated: 8088.64
> 
> * Old model
> %Cpu0  :  0.5 us, 68.8 sy,  0.0 ni, 16.1 id,  0.5 wa,  0.0 hi,  2.8 si, 11.5 st
> %Cpu1  :  0.4 us, 45.1 sy,  0.0 ni, 31.1 id,  0.4 wa,  0.0 hi,  2.1 si, 20.9 st
> %Cpu2  :  0.9 us, 44.8 sy,  0.0 ni, 30.9 id,  0.0 wa,  0.0 hi,  1.3 si, 22.2 st
> %Cpu3  :  0.8 us, 46.4 sy,  0.0 ni, 28.3 id,  1.3 wa,  0.0 hi,  2.1 si, 21.1 st
> Throughputs: 1899.14 2280.43 1963.33 1893.47 aggregated: 8036.37
> 
> We can see that the impact is mainly on CPU usage. The new model moves
> processing from kthread to NAPI (software interrupt).
> 
> Wei Liu (3):
>   xen-netback: remove page tracking facility
>   xen-netback: switch to NAPI + kthread 1:1 model
>   xen-netback: rename functions
> 
>  drivers/net/xen-netback/common.h    |  150 +++++--
>  drivers/net/xen-netback/interface.c |  135 ++++--
>  drivers/net/xen-netback/netback.c   |  833 +++++++++++------------------------
>  3 files changed, 445 insertions(+), 673 deletions(-)
> 
> -- 
> 1.7.10.4
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