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Subject: Re: [RFC][PATCH 2/3] sched: On-demand cfs_rq list
From: Peter Zijlstra <peterz@infradead.org>
To: Paul Turner <pjt@google.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Srivatsa Vaddagiri <vatsa@in.ibm.com>,
        Chris Friesen <cfriesen@nortel.com>,
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        Pierre Bourdon <pbourdon@excellency.fr>
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Date: Fri, 03 Sep 2010 09:59:29 +0200
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On Fri, 2010-09-03 at 04:33 +0100, Paul Turner wrote:
> > @@ -668,6 +693,11 @@ static void update_cfs_load(struct cfs_r
> >                cfs_rq->load_period /= 2;
> >                cfs_rq->load_avg /= 2;
> >        }
> > +
> > +       if (lb && !cfs_rq->nr_running) {
> > +               if (cfs_rq->load_period < (period / 8))
> > +                       list_del_leaf_cfs_rq(cfs_rq);
> > +       }
> >  }
> >
> 
> In the case of zero load, load_avg above will decay however
> load_period will remain in the range  [period/2, period], any entity
> that has passed period/8 time will remain on the leaf rq list.

Right, already changed that to cfs_rq->load_avg < (period / 8) after you
pointed that out on irc..

> The lb condition could also be relaxed in the dequeue_entity case.
> 
Possibly yeah, we'll have to see if that makes much difference.