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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: Nikhil Rao <ncrao@google.com>
Cc: Ingo Molnar <mingo@elte.hu>, Mike Galbraith <efault@gmx.de>,
        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 14:06:35 +0200
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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? Also the name isn't really
helpful, the comment suggests it should be called something like:
is_under_utilized().

Hmm?