linux-kernel - Re: CFQ IO scheduler patch series - AIM7 DBase results on a 16-way IA64

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Message-ID: <20070521121944.GU14746@kernel.dk>
Date:	Mon, 21 May 2007 14:19:44 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	"Alan D. Brunelle" <Alan.Brunelle@...com>
Cc:	linux-kernel@...r.kernel.org, vtaras@...nvz.org
Subject: Re: CFQ IO scheduler patch series - AIM7 DBase results on a 16-way   IA64

On Mon, May 21 2007, Alan D. Brunelle wrote:
> Jens Axboe wrote:
> >On Tue, May 01 2007, Alan D. Brunelle wrote:
> >  
> >>Jens Axboe wrote:
> >>    
> >>>On Mon, Apr 30 2007, Alan D. Brunelle wrote:
> >>>      
> >>>>The results from a single run of an AIM7 DBase load on a 16-way ia64 
> >>>>box (64GB RAM + 144 FC disks) showed a slight regression (~0.5%) by 
> >>>>adding in this patch. (Graph can be found at   
> >>>>http://free.linux.hp.com/~adb/cfq/cfq_dbase.png   ) It is only a single 
> >>>>set of runs, on a single platform, but it is something to keep an eye 
> >>>>on as the regression showed itself across the complete run.
> >>>>        
> >>>Do you know if this regression is due to worse IO performance, or
> >>>increased system CPU usage?
> >>>      
> >>We performed two point runs yesterday (20,000 and 50,000 tasks) and here 
> >>are the results:
> >>
> >>Kernel  Tasks  Jobs per Minute  %sys (avg)
> >>------  -----  ---------------  ----------
> >>2.6.21  20000     60,831.1        39.83%
> >>CFQ br  20000     60,237.4        40.80%
> >>                   -0.98%        +2.44%
> >>
> >>2.6.21  50000     60,881.6        40.43%
> >>CFQ br  50000     60,400.6        40.80%
> >>                   -0.79%        +0.92%
> >>
> >>So we're seeing a slight IO performance regression with a slight 
> >>increase in %system with the CFQ branch. (A chart of the complete run 
> >>values is up on  http://free.linux.hp.com/~adb/cfq/cfq_20k50k.png  ).
> >>    
> >
> >Alan, can you repeat that same run with this patch applied? It
> >reinstates the cfq lookup hash, which could account for increased system
> >utilization.
> >  
> 
> Hi Jens -
> 
> This test was performed over the weekend, results are updated on
> 
> http://free.linux.hp.com/~adb/cfq/cfq_dbase.png

Thanks a lot, Alan! So the cfq hash does indeed improve things a little,
that's a shame. I guess I'll just reinstate the hash lookup.

-- 
Jens Axboe

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