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Subject: Re: [patch 11/15] sched: hierarchical task accounting for
 SCHED_OTHER
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Paul Turner <pjt@google.com>
Cc: linux-kernel@vger.kernel.org, Bharata B Rao <bharata@linux.vnet.ibm.com>,
        Dhaval Giani <dhaval.giani@gmail.com>,
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        Ingo Molnar <mingo@elte.hu>, Pavel Emelyanov <xemul@openvz.org>
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Date: Tue, 05 Apr 2011 15:28:10 +0200
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On Tue, 2011-03-22 at 20:03 -0700, Paul Turner wrote:
> With task entities participating in throttled sub-trees it is possible for
> task activation/de-activation to not lead to root visible changes to
> rq->nr_running.  This in turn leads to incorrect idle and weight-per-task load
> balance decisions.
> 
> To allow correct accounting we move responsibility for updating rq->nr_running
> to the respective sched::classes.  In the fair-group case this update is
> hierarchical, tracking the number of active tasks rooted at each group entity.
> 
> This also allows us to fix a small buglet in pick_next_task() when group
> scheduling is enabled.
> 
> Note: technically this issue also exists with the existing sched_rt
> throttling; however due to the nearly complete provisioning of system
> resources for rt scheduling this is much less common by default.

Shouldn't this patch live at the start of the series?