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Subject: Re: [PATCH 4/4] sched: force balancing on newidle balance if local
 group has capacity
From: Peter Zijlstra <peterz@infradead.org>
To: Mike Galbraith <efault@gmx.de>
Cc: Nikhil Rao <ncrao@google.com>, Ingo Molnar <mingo@elte.hu>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        Venkatesh Pallipadi <venki@google.com>, linux-kernel@vger.kernel.org
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Date: Fri, 15 Oct 2010 14:20:14 +0200
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On Fri, 2010-10-15 at 14:18 +0200, Mike Galbraith wrote:
> On Fri, 2010-10-15 at 14:06 +0200, Peter Zijlstra wrote:
> > On Wed, 2010-10-13 at 12:09 -0700, Nikhil Rao wrote:
> > > +bool check_utilization(struct sd_lb_stats *sds)
> > > +{
> > > +       if (!sds->this_has_capacity || sds->busiest_has_capacity)
> > > +               return false;
> > > +
> > > +       return true;
> > > +}
> > > +
> > >  /******* find_busiest_group() helpers end here *********************/
> > >  
> > >  /**
> > > @@ -2824,6 +2845,10 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
> > >         if (!sds.busiest || sds.busiest_nr_running == 0)
> > >                 goto out_balanced;
> > >  
> > > +       /*  SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
> > > +       if (idle == CPU_NEWLY_IDLE && check_utilization(&sds))
> > > +               goto force_balance; 
> > 
> > 
> > Is that really worth an extra function?
> 
> (I did that)
> 
> No, just it made it look prettier to me.  I figured the compiler will
> nuke it at zero cost.

Sure.. but it does raise the whole naming/confusion angle ;-)