linux-kernel - Re: [PATCH] CPUIdle: Reevaluate C-states under CPU load to favor deeper C-states

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Date:	Tue, 20 Mar 2012 20:19:02 +0530
From:	melwyn lobo <linux.melwyn@...il.com>
To:	"Chalhoub, Nicole" <n-chalhoub@...com>,
	"Hilman, Kevin" <khilman@...com>
Cc:	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH] CPUIdle: Reevaluate C-states under CPU load to favor
 deeper C-states

Hey Kevin,
I would like to try out this patch in my platform see the benefits
that you are reporting. But there is one issue in this patch. You have
not initialized "hrtimer_timeout" variable.
This will always be 0 right ?.
Thanks,
-M

On Wed, Nov 9, 2011 at 11:36 PM, Chalhoub, Nicole <n-chalhoub@...com> wrote:
> Hi Deepthi,
>
>>
> Texas Instruments France SA, 821 Avenue Jack Kilby, 06270 Villeneuve Loubet. 036 420 040 R.C.S Antibes. Capital de EUR 753.920
>
> -----Original Message-----
>> From: Deepthi Dharwar [mailto:deepthi@...ux.vnet.ibm.com]
>> Sent: Wednesday, November 09, 2011 12:13 PM
>> To: Hilman, Kevin
>> Cc: linux-kernel@...r.kernel.org; Arjan van de Ven; linux-arm-
>> kernel@...ts.infradead.org; linux-omap@...r.kernel.org; linux-
>> pm@...ts.linux-foundation.org; Chalhoub, Nicole
>> Subject: Re: [PATCH] CPUIdle: Reevaluate C-states under CPU load to favor
>> deeper C-states
>
> [...]
>> By setting timers when we enter non-deepest C-state possible, such that
>> when it fires we
>> can re-evaluate and try moving into deeper and deeper C-states enhancing
>> the
>> power savings is a good feature to have.
>>
>> Looking at the current implementation, is it possible to have it as
>> configurable option
>> where one can enable/disable this functionality through the backhand
>> driver ?
>
> The timeout values of the c state timers are set in the backhand driver.
> By setting the timeout to 0 the timers will not fire so you'll not have this functionality enabled
>
>> Also I am thinking, instead of having them in governor
>> wouldnt it be a good idea to have it implemented in
>> the backhand driver itself ?
>> --Deepthi
>
>
> In fact each C-state had its own configurable timer, so it is a parameter characterizing a C-state as it is for the exit_latency and target_residency parameters.
> And we wanted the timer to fire only when we do not go in deep Cstate due to a high load. This decision is made in the CPU idle governor. So the functionality should be seen from the governor..
>
> Thanks and Regards
> Nicole
>
>
> --
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