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

["Alan D. Brunelle" <Alan.Brunelle@hp.com>]

Jens Axboe wrote:
> 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.
>
>   
You're welcome Jens, but remember: It's one set of data; from one 
benchmark; on one architecture; on one platform...don't know if you 
should scrap the whole thing for that! :-) At the very least, I could 
look into trying it out on another architecture. Let me see what I can 
dig up...

Alan
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