linux-kernel - Re: [PATCH 2/2] drivers: devfreq: add tracing for scheduling work

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Message-ID: <20190214140725.307d493c@gandalf.local.home>
Date:   Thu, 14 Feb 2019 14:07:25 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Lukasz Luba <l.luba@...tner.samsung.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        b.zolnierkie@...sung.com, myungjoo.ham@...sung.com,
        cw00.choi@...sung.com, kyungmin.park@...sung.com,
        m.szyprowski@...sung.com, s.nawrocki@...sung.com, mka@...omium.org,
        mingo@...hat.com
Subject: Re: [PATCH 2/2] drivers: devfreq: add tracing for scheduling work

On Thu, 14 Feb 2019 19:57:56 +0100
Lukasz Luba <l.luba@...tner.samsung.com> wrote:

> This patch add basic tracing of the devfreq workqueue and delayed work.
> It aims to capture changes of the polling intervals and device state.
> 
> Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>
> Signed-off-by: Lukasz Luba <l.luba@...tner.samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0ae3de7..c9714fd 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -29,6 +29,9 @@
>  #include <linux/of.h>
>  #include "governor.h"
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/devfreq.h>
> +
>  static struct class *devfreq_class;
>  
>  /*
> @@ -394,6 +397,11 @@ static void devfreq_monitor(struct work_struct *work)
>  	queue_delayed_work(devfreq_wq, &devfreq->work,
>  				msecs_to_jiffies(devfreq->profile->polling_ms));
>  	mutex_unlock(&devfreq->lock);
> +
> +	trace_devfreq_monitor(dev_name(&devfreq->dev), devfreq->previous_freq,
> +			      devfreq->profile->polling_ms,
> +			      devfreq->last_status.busy_time,
> +			      devfreq->last_status.total_time);

I would pass just devfreq into the tracepoint (it will be less work by
gcc in this code path), and do all this work in the TP__fast_assign()

The string can still handle this with:

		__string(dev_name, dev_name(&devfreq->dev))

And assigned:

		__assign_str(dev_name, dev_name(&devfreq->dev))

But the rest of fast assign should be:

	TP_fast_assign(
		__entry->freq = devfreq->previous_freq;
		__entry->busy_time = devfreq->last_status.busy_time;
		__entry->total_time = devfreq->last_status.total_time;
		__entry->polling_ms = devfreq->profile->polling_ms;
		__assign_str(dev_name, dev_name(&deqfreq->dev));
	}

-- Steve

>  }
>  
>  /**