linux-kernel - Re: A few questions and issues with dynticks, NOHZ and powertop

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Message-ID: <4BBA0AC5.1080905@linux.intel.com>
Date:	Mon, 05 Apr 2010 09:07:33 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	Dominik Brodowski <linux@...inikbrodowski.net>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Dmitry Torokhov <dtor@...l.ru>
Subject: Re: A few questions and issues with dynticks, NOHZ and powertop

On 4/5/2010 8:14, Paul E. McKenney wrote:
> So the main issue is that for many workloads, it is best to run full bore
> and get done quickly, thus allowing the entire machine to be powered down?

yep

>
> If so, it seems likely that there would be some workloads that were sometimes
> unable to use all the CPUs, in which case shutting down (idling, offlining,
> dyntick-idling, whatever) the excess CPUs might nevertheless be the right
> thing to do.

but the point is that the normal scheduler + idle behavior gives you exactly that
in a natural way !
If you don't have enough work (tasks) to keep all cores busy, the others are and stay idle.
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