linux-kernel - Re: [PATCH V2 14/16] cpuidle: don't calculate time-diff if entered

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Date:	Thu, 21 Nov 2013 02:06:04 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Patch Tracking <patches@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH V2 14/16] cpuidle: don't calculate time-diff if entered_state < 0

On Wednesday, November 20, 2013 01:34:45 PM Viresh Kumar wrote:
> On 3 October 2013 21:26, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> > If entered_state < 0, we don't need to set dev->last_residency to 'diff' as we
> > will be setting it to zero without using its new value.
> >
> > And so move calculation of diff also inside the "if" statement.
> >
> > Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> > Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> > ---
> >  drivers/cpuidle/cpuidle.c | 17 +++++++++--------
> >  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> Missed applying this one too?

No, I didn't.  I just thought it wasn't worth it ...

> >
> > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> > index b45257a..1a6e9f5 100644
> > --- a/drivers/cpuidle/cpuidle.c
> > +++ b/drivers/cpuidle/cpuidle.c
> > @@ -77,23 +77,22 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
> >
> >         struct cpuidle_state *target_state = &drv->states[index];
> >         ktime_t time_start, time_end;
> > -       s64 diff;
> >
> >         time_start = ktime_get();
> >
> >         entered_state = target_state->enter(dev, drv, index);
> >
> > -       time_end = ktime_get();
> > +       if (entered_state >= 0) {
> > +               s64 diff;
> >
> > -       local_irq_enable();
> > +               time_end = ktime_get();
> > +               diff = ktime_to_us(ktime_sub(time_end, time_start));
> >
> > -       diff = ktime_to_us(ktime_sub(time_end, time_start));
> > -       if (diff > INT_MAX)
> > -               diff = INT_MAX;
> > +               if (diff > INT_MAX)
> > +                       diff = INT_MAX;
> >
> > -       dev->last_residency = (int) diff;
> > +               dev->last_residency = (int) diff;
> >
> > -       if (entered_state >= 0) {
> >                 /* Update cpuidle counters */
> >                 /* This can be moved to within driver enter routine
> >                  * but that results in multiple copies of same code.
> > @@ -104,6 +103,8 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
> >                 dev->last_residency = 0;
> >         }
> >
> > +       local_irq_enable();
> > +
> >         return entered_state;
> >  }
> >
> > --
> > 1.7.12.rc2.18.g61b472e
> >
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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