linux-kernel - Re: [PATCH 2/4] timer: relax tick stop in idle entry

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Message-ID: <alpine.DEB.2.11.1511131516180.3987@nanos>
Date:	Fri, 13 Nov 2015 15:22:16 -0500 (EST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Paul Turner <pjt@...gle.com>
Subject: Re: [PATCH 2/4] timer: relax tick stop in idle entry



On Fri, 13 Nov 2015, Jacob Pan wrote:

> Upon entering idle, we can turn off tick if the next timeout
> is exactly one tick away. Otherwise, we could enter inner idle loop
> with tick still enabled, without resched set, the tick will continue
> during idle therefore less optimal in terms of energy savings.

This does not make any sense at all. 

next_tick is the next required tick event. If it's exactly ONE tick
away why should we go through the hassle of stopping it? Just to
cancel the timer and then set it to the same value again? Oh well.

Thanks,

	tglx


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