linux-kernel - Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task enqueue/dequeue

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Message-ID: <alpine.DEB.2.20.1601201041560.24351@east.gentwo.org>
Date:	Wed, 20 Jan 2016 10:42:56 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Byungchul Park <byungchul.park@....com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mike Galbraith <efault@....de>, Rik van Riel <riel@...hat.com>
Subject: Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task
 enqueue/dequeue

On Wed, 20 Jan 2016, Frederic Weisbecker wrote:

> > So we agreed long time ago, that we first fix the issues with s single task
> > running undisturbed in user space, i.e. tickless. Those issues have never been
> > resolved fully, but now you try to add more complexity of extra runnable
> > tasks, nohz tasks sleeping and whatever.
>
> Nohz tasks do sleep, really, at least we need to handle that case now.

Sleep meaning call into the OS to be put to sleep? Why would NOHZ be
active then?