Re: [PATCH v3 linux-next] cpufreq: ondemand: Calculate gradient of CPU load to early increase frequency

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Saturday, March 30, 2013 12:27:34 AM Stratos Karafotis wrote:
> On 02/22/2013 03:56 AM, Viresh Kumar wrote:
> > On 21 February 2013 23:09, Stratos Karafotis <stratosk@semaphore.gr> wrote:
> >
> >> Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
> > 
> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> > 
> 
> Hi Rafael,
> 
> In case you are interested in this patch I rebased it to the latest linux-pm/bleeding-edge.

Thanks!

I have a backlog of cpufreq patches to sort out, so it may take some time till
I get to this one.

Thanks,
Rafael


> ------------------------------------------
> Instead of checking only the absolute value of CPU load_freq to increase
> frequency, we detect forthcoming CPU load rise and increase frequency
> earlier.
> 
> Every sampling rate, we calculate the gradient of load_freq. If it is
> too steep we assume that the load most probably will go over
> up_threshold in next iteration(s) and we increase frequency immediately.
> 
> New tuners are introduced:
> - early_demand: to enable this functionality (disabled by default).
> - grad_up_threshold: over this gradient of load we will increase
> frequency immediately.
> 
> Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
> ---
>  drivers/cpufreq/cpufreq_governor.c |  1 +
>  drivers/cpufreq/cpufreq_governor.h |  3 ++
>  drivers/cpufreq/cpufreq_ondemand.c | 59 +++++++++++++++++++++++++++++++++++++-
>  3 files changed, 62 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> index 41e5e56..1d9abc4 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -328,6 +328,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy,
>  		} else {
>  			od_dbs_info->rate_mult = 1;
>  			od_dbs_info->sample_type = OD_NORMAL_SAMPLE;
> +			od_dbs_info->prev_load_freq = 0;
>  			od_ops->powersave_bias_init_cpu(cpu);
>  		}
>  
> diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
> index 1f7de13..c33b37a 100644
> --- a/drivers/cpufreq/cpufreq_governor.h
> +++ b/drivers/cpufreq/cpufreq_governor.h
> @@ -95,6 +95,7 @@ struct od_cpu_dbs_info_s {
>  	unsigned int freq_hi_jiffies;
>  	unsigned int rate_mult;
>  	unsigned int sample_type:1;
> +	unsigned int prev_load_freq;
>  };
>  
>  struct cs_cpu_dbs_info_s {
> @@ -113,6 +114,8 @@ struct od_dbs_tuners {
>  	unsigned int adj_up_threshold;
>  	unsigned int powersave_bias;
>  	unsigned int io_is_busy;
> +	unsigned int grad_up_threshold;
> +	unsigned int early_demand;
>  };
>  
>  struct cs_dbs_tuners {
> diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
> index 29ed48a..6cd59a7 100644
> --- a/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/drivers/cpufreq/cpufreq_ondemand.c
> @@ -31,6 +31,7 @@
>  #define DEF_FREQUENCY_DOWN_DIFFERENTIAL		(10)
>  #define DEF_FREQUENCY_UP_THRESHOLD		(80)
>  #define DEF_SAMPLING_DOWN_FACTOR		(1)
> +#define DEF_GRAD_UP_THRESHOLD			(50)
>  #define MAX_SAMPLING_DOWN_FACTOR		(100000)
>  #define MICRO_FREQUENCY_DOWN_DIFFERENTIAL	(3)
>  #define MICRO_FREQUENCY_UP_THRESHOLD		(95)
> @@ -168,11 +169,26 @@ static void od_check_cpu(int cpu, unsigned int load_freq)
>  	struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;
>  	struct dbs_data *dbs_data = policy->governor_data;
>  	struct od_dbs_tuners *od_tuners = dbs_data->tuners;
> +	int boost_freq = 0;
>  
>  	dbs_info->freq_lo = 0;
>  
> +	/*
> +	 * Calculate the gradient of load_freq. If it is too steep we assume
> +	 * that the load will go over up_threshold in next iteration(s) and
> +	 * we increase the frequency immediately
> +	 */
> +	if (od_tuners->early_demand) {
> +		if (load_freq > dbs_info->prev_load_freq &&
> +		   (load_freq - dbs_info->prev_load_freq >
> +		    od_tuners->grad_up_threshold * policy->cur))
> +			boost_freq = 1;
> +
> +		dbs_info->prev_load_freq = load_freq;
> +	}
> +
>  	/* Check for frequency increase */
> -	if (load_freq > od_tuners->up_threshold * policy->cur) {
> +	if (boost_freq || load_freq > od_tuners->up_threshold * policy->cur) {
>  		/* If switching to max speed, apply sampling_down_factor */
>  		if (policy->cur < policy->max)
>  			dbs_info->rate_mult =
> @@ -454,12 +470,47 @@ static ssize_t store_powersave_bias(struct cpufreq_policy *policy,
>  	return count;
>  }
>  
> +static ssize_t store_grad_up_threshold(struct cpufreq_policy *policy,
> +		const char *buf, size_t count)
> +{
> +	struct dbs_data *dbs_data = policy->governor_data;
> +	struct od_dbs_tuners *od_tuners = dbs_data->tuners;
> +	unsigned int input;
> +	int ret;
> +	ret = sscanf(buf, "%u", &input);
> +
> +	if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
> +			input < MIN_FREQUENCY_UP_THRESHOLD) {
> +		return -EINVAL;
> +	}
> +
> +	od_tuners->grad_up_threshold = input;
> +	return count;
> +}
> +
> +static ssize_t store_early_demand(struct cpufreq_policy *policy,
> +		const char *buf, size_t count)
> +{
> +	struct dbs_data *dbs_data = policy->governor_data;
> +	struct od_dbs_tuners *od_tuners = dbs_data->tuners;
> +	unsigned int input;
> +	int ret;
> +
> +	ret = sscanf(buf, "%u", &input);
> +	if (ret != 1)
> +		return -EINVAL;
> +	od_tuners->early_demand = !!input;
> +	return count;
> +}
> +
>  show_one(od, sampling_rate, sampling_rate);
>  show_one(od, io_is_busy, io_is_busy);
>  show_one(od, up_threshold, up_threshold);
>  show_one(od, sampling_down_factor, sampling_down_factor);
>  show_one(od, ignore_nice, ignore_nice);
>  show_one(od, powersave_bias, powersave_bias);
> +show_one(od, grad_up_threshold, grad_up_threshold);
> +show_one(od, early_demand, early_demand);
>  declare_show_sampling_rate_min();
>  
>  cpufreq_freq_attr_rw(sampling_rate);
> @@ -468,6 +519,8 @@ cpufreq_freq_attr_rw(up_threshold);
>  cpufreq_freq_attr_rw(sampling_down_factor);
>  cpufreq_freq_attr_rw(ignore_nice);
>  cpufreq_freq_attr_rw(powersave_bias);
> +cpufreq_freq_attr_rw(grad_up_threshold);
> +cpufreq_freq_attr_rw(early_demand);
>  cpufreq_freq_attr_ro(sampling_rate_min);
>  
>  static struct attribute *dbs_attributes[] = {
> @@ -478,6 +531,8 @@ static struct attribute *dbs_attributes[] = {
>  	&ignore_nice.attr,
>  	&powersave_bias.attr,
>  	&io_is_busy.attr,
> +	&grad_up_threshold.attr,
> +	&early_demand.attr,
>  	NULL
>  };
>  
> @@ -525,9 +580,11 @@ static int od_init(struct dbs_data *dbs_data)
>  	}
>  
>  	tuners->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
> +	tuners->grad_up_threshold = DEF_GRAD_UP_THRESHOLD;
>  	tuners->ignore_nice = 0;
>  	tuners->powersave_bias = 0;
>  	tuners->io_is_busy = should_io_be_busy();
> +	tuners->early_demand = 0;
>  
>  	dbs_data->tuners = tuners;
>  	mutex_init(&dbs_data->mutex);
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.