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

melwyn lobo [off-list ref] writes:

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 ?.

Correct.

The generic code defaults to zero so that the default behavior with this
patch is unchanged from previous behavior.  In order to use this
feature, your platform-specific code which creates your C-states sets
the per-C-state timer values.

Kevin

Thanks,
-M

On Wed, Nov 9, 2011 at 11:36 PM, Chalhoub, Nicole [off-list ref] wrote:

quoted

Hi Deepthi,

quoted

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-----

quoted

From: Deepthi Dharwar [mailto:deepthi at linux.vnet.ibm.com]
Sent: Wednesday, November 09, 2011 12:13 PM
To: Hilman, Kevin
Cc: linux-kernel at vger.kernel.org; Arjan van de Ven; linux-arm-
kernel at lists.infradead.org; linux-omap at vger.kernel.org; linux-
pm at lists.linux-foundation.org; Chalhoub, Nicole
Subject: Re: [PATCH] CPUIdle: Reevaluate C-states under CPU load to favor
deeper C-states

[...]

quoted

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

quoted

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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