linux-kernel - Re: [PATCH] cpuidle: Measure idle state durations with monotonic clock

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Message-ID: <50B45A47.9050600@kernel.org>
Date:	Tue, 27 Nov 2012 01:14:31 -0500
From:	Len Brown <lenb@...nel.org>
To:	Preeti Murthy <preeti.lkml@...il.com>
CC:	Julius Werner <jwerner@...omium.org>, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, Kevin Hilman <khilman@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	linux-acpi@...r.kernel.org, linux-pm@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>,
	Trinabh Gupta <g.trinabh@...il.com>,
	Sameer Nanda <snanda@...omium.org>,
	Lists Linaro-dev <linaro-dev@...ts.linaro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] cpuidle: Measure idle state durations with monotonic
 clock

On 11/15/2012 04:04 AM, Preeti Murthy wrote:
> Hi all,
> 
> The code looks correct and inviting to me as it has led to good cleanups.
> I dont think passing 0 as the argument to the function
> sched_clock_idle_wakeup_event()
> should lead to problems,as it does not do anything useful with the
> passed arguments.
> 
> My only curiosity is what was the purpose of passing idle residency time to
> sched_clock_idle_wakeup_event() when this data could always be retrieved from
> dev->last_residency for each cpu,which gets almost immediately updated.

sched_clock_idle_wakeup_event() is part of the scheduler.
The scheduler doesn't know what a cpuidle_device is, and
probably should not grow such a dependency.

cheers,
-Len Brown, Intel Open Source Technology Center

> But this does not seem to come in way of this patch for now.Anyway I
> have added Peter to
> the list so that he can opine about this issue if possible and needed.
> 
> Reviewed-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
> 
> 
> Regards
> Preeti U Murthy
> 

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