linux-kernel - Re: [PATCH 2/3] PM / devfreq: fix stats start time stamp

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Message-ID: <CAJ0PZbQ1FOk0LMxDCpANqAJ5MOciGy1fvyN__TrEgTGRz-63KA@mail.gmail.com>
Date:	Mon, 14 Jan 2013 23:42:14 +0900
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	Rajagopal Venkat <rajagopal.venkat@...aro.org>,
	jonghwa3.lee@...sung.com
Cc:	kyungmin.park@...sung.com, mturquette@...aro.org, rjw@...k.pl,
	patches@...aro.org, linaro-dev@...ts.linaro.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] PM / devfreq: fix stats start time stamp

On Tue, Jan 8, 2013 at 2:50 PM, Rajagopal Venkat
<rajagopal.venkat@...aro.org> wrote:
> Mark the stats start time stamp when actual load monitoring is
> started for accuracy.
>

It appears that you are changing the semantics of the information here.


For example, in the case:
- devfreq started at 0 w/ 100MHz
- at 10, devfreq monitor starts w/ 100MHz
- at 20, devfreq updates the freq to 200MHz
- at 30, devfreq is requested to show the stat

The conventional:
20 @ 100MHz / 10 @ 200MHz

You proposed:
10 @ 100MHz / 10 @ 200MHz


Could you please give some reasons why the latter is "more accurate"?
To me, the former seems appropriate.



Cheers,
MyungJoo


> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@...aro.org>
> ---
>  drivers/devfreq/devfreq.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 5782c9b..2843a22 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -254,9 +254,12 @@ static void devfreq_monitor(struct work_struct *work)
>  void devfreq_monitor_start(struct devfreq *devfreq)
>  {
>         INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
> -       if (devfreq->profile->polling_ms)
> +       if (devfreq->profile->polling_ms) {
>                 queue_delayed_work(devfreq_wq, &devfreq->work,
>                         msecs_to_jiffies(devfreq->profile->polling_ms));
> +
> +               devfreq->last_stat_updated = jiffies;
> +       }
>  }
>  EXPORT_SYMBOL(devfreq_monitor_start);
>
> @@ -498,7 +501,6 @@ struct devfreq *devfreq_add_device(struct device *dev,
>         devfreq->time_in_state = devm_kzalloc(dev, sizeof(unsigned int) *
>                                                 devfreq->profile->max_state,
>                                                 GFP_KERNEL);
> -       devfreq->last_stat_updated = jiffies;
>         devfreq_set_freq_limits(devfreq);
>
>         dev_set_name(&devfreq->dev, dev_name(dev));
> --
> 1.7.10.4
>
> --
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-- 
MyungJoo Ham, Ph.D.
Mobile Software Platform Lab, DMC Business, Samsung Electronics
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