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Date: Thu, 18 Jan 2018 10:32:34 +0000
From: Morten Rasmussen <morten.rasmussen@foss.arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
        Ingo Molnar <mingo@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Brendan Jackman <brendan.jackman@arm.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>
Subject: Re: [RFC PATCH 2/5] sched: Add NOHZ_STATS_KICK
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On Mon, Jan 15, 2018 at 10:43:18AM +0100, Peter Zijlstra wrote:
> On Tue, Jan 02, 2018 at 03:44:57PM +0000, Morten Rasmussen wrote:
> 
> > Vincent already proposed, why can't we just modify Brendan's
> > CPU_NEWLY_IDLE proposal to do a stats update from idle_balance() every
> > 32ms regardless of whether we need to load-balance?
> 
> I think that code is there, no?
> 
> Subject: sched: Update blocked load from NEWIDLE

The mechanics are there, but I think the problem is that the
idle_balance() bails out before we get to it in some cases. If we only
have a few small periodic tasks running rd->overload won't be set and
idle_balance() returns before doing anything.

We would need some sort of check to see if a PELT update is due and make
sure it happens, even if idle_balance() has nothing to do.