linux-kernel - Re: [PATCH 1/4] sched: Don't account tickless CPU load on tick

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Message-ID: <20160119130857.GC6344@twins.programming.kicks-ass.net>
Date:	Tue, 19 Jan 2016 14:08:57 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Byungchul Park <byungchul.park@....com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mike Galbraith <efault@....de>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 1/4] sched: Don't account tickless CPU load on tick

On Wed, Jan 13, 2016 at 05:01:28PM +0100, Frederic Weisbecker wrote:
> The cpu load update on tick doesn't care about dynticks and as such is
> buggy when occuring on nohz ticks (including idle ticks) as it resets
> the jiffies snapshot that was recorded on nohz entry. We eventually
> ignore the potentially long tickless load that happened before the
> tick.

I don't get it, how can we call scheduler_tick() while
tick_nohz_tick_stopped() ?