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Subject: Re: [PATCH v2 3/3] devfreq: move statistics to separate struct
To:     Matthias Kaehlcke <mka@chromium.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>
From:   Kamil Konieczny <k.konieczny@samsung.com>
Message-ID: <d2bc3e5f-3170-4dff-9ce6-ceb2555ae0ba@samsung.com>
Date:   Thu, 5 Dec 2019 15:18:21 +0100
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Sender: linux-kernel-owner@vger.kernel.org
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Hi,

thank you for review, I will follow you suggestions in v3.

On 05.12.2019 01:28, Matthias Kaehlcke wrote:
> Hi,
> 
> On Wed, Dec 04, 2019 at 04:00:18PM +0100, Kamil Konieczny wrote:
>> Count time and transitions between devfreq frequencies in separate struct
>> for improved code readability and maintenance.
>>
>> Signed-off-by: Kamil Konieczny <k.konieczny@samsung.com>
>> ---
>> Changes in v2:
>>  squash three patches into one, do not modify devfreq_profile and separate stats
>>  into devfreq_stats
>>
>>  drivers/devfreq/devfreq.c | 68 +++++++++++++++++++++++----------------
>>  include/linux/devfreq.h   | 31 ++++++++++++------
>>  2 files changed, 62 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 901af3b66a76..4d50c8f10bd2 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -198,6 +198,7 @@ static int set_freq_table(struct devfreq *devfreq)
>>   */
>>  int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  {
>> +	struct devfreq_stats *stats = devfreq->stats;
>>  	int lev, prev_lev, ret = 0;
>>  	unsigned long long cur_time;
>>  
>> @@ -214,8 +215,8 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  		goto out;
>>  	}
>>  
>> -	devfreq->time_in_state[prev_lev] +=
>> -			 cur_time - devfreq->last_stat_updated;
>> +	stats->time_in_state[prev_lev] +=
>> +			 cur_time - stats->last_stat_updated;
>>  
>>  	lev = devfreq_get_freq_level(devfreq, freq);
>>  	if (lev < 0) {
>> @@ -224,13 +225,12 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  	}
>>  
>>  	if (lev != prev_lev) {
>> -		devfreq->trans_table[(prev_lev *
>> -				devfreq->profile->max_state) + lev]++;
>> -		devfreq->total_trans++;
>> +		stats->trans_table[(prev_lev * stats->max_state) + lev]++;
>> +		stats->total_trans++;
>>  	}
>>  
>>  out:
>> -	devfreq->last_stat_updated = cur_time;
>> +	stats->last_stat_updated = cur_time;
>>  	return ret;
>>  }
>>  EXPORT_SYMBOL(devfreq_update_status);
>> @@ -525,7 +525,7 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
>>  			msecs_to_jiffies(devfreq->profile->polling_ms));
>>  
>>  out_update:
>> -	devfreq->last_stat_updated = get_jiffies_64();
>> +	devfreq->stats->last_stat_updated = get_jiffies_64();
>>  	devfreq->stop_polling = false;
>>  
>>  	if (devfreq->profile->get_cur_freq &&
>> @@ -735,28 +735,38 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  		goto err_out;
>>  	}
>>  
>> -	devfreq->trans_table = devm_kzalloc(&devfreq->dev,
>> +	devfreq->stats = devm_kzalloc(&devfreq->dev, sizeof(*devfreq->stats),
>> +				      GFP_KERNEL);
>> +	if (!devfreq->stats) {
>> +		mutex_unlock(&devfreq->lock);
>> +		err = -ENOMEM;
>> +		goto err_devfreq;
>> +	}
>> +
>> +	devfreq->stats->freq_table = devfreq->profile->freq_table;
>> +	devfreq->stats->max_state = devfreq->profile->max_state;
>> +	devfreq->stats->trans_table = devm_kzalloc(&devfreq->dev,
>>  			array3_size(sizeof(unsigned int),
>> -				    devfreq->profile->max_state,
>> -				    devfreq->profile->max_state),
>> +				    devfreq->stats->max_state,
>> +				    devfreq->stats->max_state),
>>  			GFP_KERNEL);
>> -	if (!devfreq->trans_table) {
>> +	if (!devfreq->stats->trans_table) {
>>  		mutex_unlock(&devfreq->lock);
>>  		err = -ENOMEM;
>>  		goto err_devfreq;
>>  	}
>>  
>> -	devfreq->time_in_state = devm_kcalloc(&devfreq->dev,
>> -			devfreq->profile->max_state,
>> -			sizeof(*devfreq->time_in_state),
>> +	devfreq->stats->time_in_state = devm_kcalloc(&devfreq->dev,
>> +			devfreq->stats->max_state,
>> +			sizeof(*devfreq->stats->time_in_state),
>>  			GFP_KERNEL);
>> -	if (!devfreq->time_in_state) {
>> +	if (!devfreq->stats->time_in_state) {
>>  		mutex_unlock(&devfreq->lock);
>>  		err = -ENOMEM;
>>  		goto err_devfreq;
>>  	}
>>  
>> -	devfreq->last_stat_updated = get_jiffies_64();
>> +	devfreq->stats->last_stat_updated = get_jiffies_64();
>>  
>>  	srcu_init_notifier_head(&devfreq->transition_notifier_list);
>>  
>> @@ -1435,9 +1445,10 @@ static ssize_t trans_stat_show(struct device *dev,
>>  			       struct device_attribute *attr, char *buf)
>>  {
>>  	struct devfreq *devfreq = to_devfreq(dev);
>> +	struct devfreq_stats *stats = devfreq->stats;
>> +	unsigned int max_state = stats->max_state;
>>  	ssize_t len;
>>  	int i, j;
>> -	unsigned int max_state = devfreq->profile->max_state;
>>  
>>  	if (max_state == 0)
>>  		return sprintf(buf, "Not Supported.\n");
>> @@ -1454,28 +1465,28 @@ static ssize_t trans_stat_show(struct device *dev,
>>  	len += sprintf(buf + len, "           :");
>>  	for (i = 0; i < max_state; i++)
>>  		len += sprintf(buf + len, "%10lu",
>> -				devfreq->profile->freq_table[i]);
>> +				stats->freq_table[i]);
>>  
>>  	len += sprintf(buf + len, "   time(ms)\n");
>>  
>>  	for (i = 0; i < max_state; i++) {
>> -		if (devfreq->profile->freq_table[i]
>> +		if (stats->freq_table[i]
>>  					== devfreq->previous_freq) {
>>  			len += sprintf(buf + len, "*");
>>  		} else {
>>  			len += sprintf(buf + len, " ");
>>  		}
>>  		len += sprintf(buf + len, "%10lu:",
>> -				devfreq->profile->freq_table[i]);
>> +				stats->freq_table[i]);
>>  		for (j = 0; j < max_state; j++)
>>  			len += sprintf(buf + len, "%10u",
>> -				devfreq->trans_table[(i * max_state) + j]);
>> +				stats->trans_table[(i * max_state) + j]);
>>  		len += sprintf(buf + len, "%10llu\n", (u64)
>> -			jiffies64_to_msecs(devfreq->time_in_state[i]));
>> +			jiffies64_to_msecs(stats->time_in_state[i]));
>>  	}
>>  
>>  	len += sprintf(buf + len, "Total transition : %u\n",
>> -					devfreq->total_trans);
>> +					stats->total_trans);
>>  	return len;
>>  }
>>  
>> @@ -1484,16 +1495,17 @@ static ssize_t trans_stat_store(struct device *dev,
>>  				const char *buf, size_t count)
>>  {
>>  	struct devfreq *df = to_devfreq(dev);
>> -	unsigned int cnt = df->profile->max_state;
>> +	struct devfreq_stats *stats = df->stats;
>> +	unsigned int cnt = stats->max_state;
>>  
>>  	if (cnt == 0)
>>  		return count;
>>  
>>  	mutex_lock(&df->lock);
>> -	memset(df->time_in_state, 0, cnt * sizeof(u64));
>> -	memset(df->trans_table, 0, cnt * cnt * sizeof(int));
>> -	df->last_stat_updated = get_jiffies_64();
>> -	df->total_trans = 0;
>> +	memset(stats->time_in_state, 0, cnt * sizeof(u64));
>> +	memset(stats->trans_table, 0, cnt * cnt * sizeof(int));
>> +	stats->last_stat_updated = get_jiffies_64();
>> +	stats->total_trans = 0;
>>  	mutex_unlock(&df->lock);
>>  
>>  	return count;
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index b81a86e47fb9..2715719924e7 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -106,6 +106,25 @@ struct devfreq_dev_profile {
>>  	unsigned int max_state;
>>  };
>>  
>> +/**
>> + * struct devfreq_stats - Devfreq's transitions stats counters
>> + * @freq_table:		List of frequencies in ascending order.
>> + * @max_state:		The size of freq_table.
>> + * @total_trans:	Number of devfreq transitions.
>> + * @trans_table:	Statistics of devfreq transitions.
>> + * @time_in_state:	Statistics of devfreq states.
>> + * @last_stat_updated:	The last time stats were updated.
>> + */
>> +struct devfreq_stats {
>> +	unsigned long *freq_table;
> 
> nit: trans_stat_show() is the only place where 'freq_table' is
> used. Instead of 'duplicating' it (I know, it's just a pointer)
> you could use a local pointer 'freq_table' in trans_stat_show().
> 
>> +	unsigned int max_state;
> 
> nit: max_state is also a bit of a corner case. It's not really a 'stat' and
> it is already available in struct devfreq_dev_profile, it doesn't seem a
> huge inconvenient to take it from there.

Good hints, I will change this.

>> +
>> +	unsigned int total_trans;
>> +	unsigned int *trans_table;
>> +	u64 *time_in_state;
>> +	unsigned long long last_stat_updated;
> 
> nit: the name 'last_stat_updated' is somewhat redundant, since the
> field is part of a struct called 'devfreq_stats'. 'last_updated' or
> 'last_update' would be concise enough IMO.

This is also good hint.

>> +};
>> +
>>  /**
>>   * struct devfreq - Device devfreq structure
>>   * @node:	list node - contains the devices with devfreq that have been
>> @@ -131,10 +150,7 @@ struct devfreq_dev_profile {
>>   * @suspend_freq:	 frequency of a device set during suspend phase.
>>   * @resume_freq:	 frequency of a device set in resume phase.
>>   * @suspend_count:	 suspend requests counter for a device.
>> - * @total_trans:	Number of devfreq transitions
>> - * @trans_table:	Statistics of devfreq transitions
>> - * @time_in_state:	Statistics of devfreq states
>> - * @last_stat_updated:	The last time stat updated
>> + * @stats:	Statistics of devfreq transitions and states times
>>   * @transition_notifier_list: list head of DEVFREQ_TRANSITION_NOTIFIER notifier
>>   *
>>   * This structure stores the devfreq information for a give device.
>> @@ -171,11 +187,8 @@ struct devfreq {
>>  	unsigned long resume_freq;
>>  	atomic_t suspend_count;
>>  
>> -	/* information for device frequency transition */
>> -	unsigned int total_trans;
>> -	unsigned int *trans_table;
>> -	u64 *time_in_state;
>> -	unsigned long long last_stat_updated;
>> +	/* information for device frequency transitions */
>> +	struct devfreq_stats *stats;
>>  
>>  	struct srcu_notifier_head transition_notifier_list;
>>  };
> 
> My comments above are just suggestions:
> 
> Reviewed-by: Matthias Kaehlcke <mka@chromium.org>

-- 
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland