linux-kernel - Re: [PATCH tip/core/rcu] Do not keep timekeeping CPU tick running for non-nohz

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Message-ID: <20140720203417.GV9918@twins.programming.kicks-ass.net>
Date:	Sun, 20 Jul 2014 22:34:17 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org,
	dhowells@...hat.com, edumazet@...gle.com, dvhart@...ux.intel.com,
	oleg@...hat.com, bobby.prani@...il.com
Subject: Re: [PATCH tip/core/rcu] Do not keep timekeeping CPU tick running
 for non-nohz_full= CPUs

On Sun, Jul 20, 2014 at 04:47:59AM -0700, Paul E. McKenney wrote:
> So we really have to have -all- the CPUs be idle to turn off the timekeeper.

That seems to be pretty unavoidable any which way around.

> This won't make the battery-powered embedded guys happy...
> 
> Other thoughts on this?  We really should not be setting
> CONFIG_NO_HZ_FULL_SYSIDLE by default until this is solved.

What are those same guys doing with nohz_full to begin with?

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