linux-kernel - Re: [RFD PATCH 02/10] cpuidle: Checking the zero latency inside the governors does not make sense.

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Date:	Mon, 27 Oct 2014 23:11:15 -0400
From:	Len Brown <lenb@...nel.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	axboe@...nel.dk, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	preeti@...ux.vnet.ibm.com,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	mturquette@...aro.org,
	Tuukka Tikkanen <tuukka.tikkanen@...aro.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Patch Tracking <patches@...aro.org>
Subject: Re: [RFD PATCH 02/10] cpuidle: Checking the zero latency inside the
 governors does not make sense.

after the patch '[V2,1/5] sched: idle: cpuidle: Check the latency req
before idle' is applied,
this one becomes a no-op.

indeed, they'd conflict both logically and physically.
physically the check for latency_req == 0 was already removed from the
governors.
logically, the upper level, cpu_idle_loop() already invokes
cpu_idle_poll() directly
when latency_req is 0.  Indeed, that would prevent the code in this
patch from running
at all, since cpu_idle_call() is no longer invoked in that case.
Further, why would
you propose invoking "use_default" instead of cpu_idle_poll() in the
latency_req == 0 case?

thanks,
Len Brown, Intel Open Source Technology Center
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