linux-kernel - Re: [PATCH v2 1/3] devfreq: change time stats to 64-bit

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Date:   Thu, 5 Dec 2019 09:27:08 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Kamil Konieczny <k.konieczny@...sung.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Subject: Re: [PATCH v2 1/3] devfreq: change time stats to 64-bit

On 12/5/19 12:00 AM, Kamil Konieczny wrote:
> Change time stats counting to bigger type by using 64-bit jiffies.
> This will make devfreq stats code look similar to cpufreq stats and
> prevents overflow (for HZ = 1000 after 49.7 days).
> 
> Signed-off-by: Kamil Konieczny <k.konieczny@...sung.com>
> Acked-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
> Changes in v2:
>  added Acked-by, rebased on linux-next
> 
>  drivers/devfreq/devfreq.c | 14 +++++++-------
>  include/linux/devfreq.h   |  4 ++--
>  2 files changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index bdeb4189c978..0e2030403e4a 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -199,10 +199,10 @@ static int set_freq_table(struct devfreq *devfreq)
>  int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>  {
>  	int lev, prev_lev, ret = 0;
> -	unsigned long cur_time;
> +	unsigned long long cur_time;

It looks better to use 'u64' instead of 'unsigned long long'.
Because get_jiffies_u64 has 'u64' return type.

>  
>  	lockdep_assert_held(&devfreq->lock);
> -	cur_time = jiffies;
> +	cur_time = get_jiffies_64();
>  
>  	/* Immediately exit if previous_freq is not initialized yet. */
>  	if (!devfreq->previous_freq)
> @@ -525,7 +525,7 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
>  			msecs_to_jiffies(devfreq->profile->polling_ms));
>  
>  out_update:
> -	devfreq->last_stat_updated = jiffies;
> +	devfreq->last_stat_updated = get_jiffies_64();
>  	devfreq->stop_polling = false;
>  
>  	if (devfreq->profile->get_cur_freq &&
> @@ -748,7 +748,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  
>  	devfreq->time_in_state = devm_kcalloc(&devfreq->dev,
>  			devfreq->profile->max_state,
> -			sizeof(unsigned long),
> +			sizeof(*devfreq->time_in_state),
>  			GFP_KERNEL);
>  	if (!devfreq->time_in_state) {
>  		mutex_unlock(&devfreq->lock);
> @@ -756,7 +756,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  		goto err_devfreq;
>  	}
>  
> -	devfreq->last_stat_updated = jiffies;
> +	devfreq->last_stat_updated = get_jiffies_64();
>  
>  	srcu_init_notifier_head(&devfreq->transition_notifier_list);
>  
> @@ -1470,8 +1470,8 @@ static ssize_t trans_stat_show(struct device *dev,
>  		for (j = 0; j < max_state; j++)
>  			len += sprintf(buf + len, "%10u",
>  				devfreq->trans_table[(i * max_state) + j]);
> -		len += sprintf(buf + len, "%10u\n",
> -			jiffies_to_msecs(devfreq->time_in_state[i]));
> +		len += sprintf(buf + len, "%10llu\n", (u64)
> +			jiffies64_to_msecs(devfreq->time_in_state[i]));
>  	}
>  
>  	len += sprintf(buf + len, "Total transition : %u\n",
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 2bae9ed3c783..b81a86e47fb9 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -174,8 +174,8 @@ struct devfreq {
>  	/* information for device frequency transition */
>  	unsigned int total_trans;
>  	unsigned int *trans_table;
> -	unsigned long *time_in_state;
> -	unsigned long last_stat_updated;
> +	u64 *time_in_state;
> +	unsigned long long last_stat_updated;

ditto. 'unsigned long long' -> 'u64'.

>  
>  	struct srcu_notifier_head transition_notifier_list;
>  };
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics