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Commit ccb2fe20 authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Dave Jones
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[CPUFREQ] Remove slowdown from ondemand sampling path. 



Remove slowdown from ondemand sampling path. This reduces the code path length
in dbs_check_cpu() by half. slowdown was not used by ondemand by default.
If there are any user level tools that were using this tunable, they
may report error now.

Signed-off-by: default avatarAlexey Starikovskiy <alexey.y.starikovskiy@intel.com>
Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarDave Jones <davej@redhat.com>
parent 501b7c77

drivers/cpufreq/cpufreq_ondemand.c

+40 −98
Original line number Diff line number Diff line
@@ -56,16 +56,14 @@ static unsigned int def_sampling_rate; 
#define MIN_SAMPLING_RATE			(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)

#define MAX_SAMPLING_RATE			(500 * def_sampling_rate)

#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER	(1000)

#define DEF_SAMPLING_DOWN_FACTOR		(1)

#define MAX_SAMPLING_DOWN_FACTOR		(10)

#define TRANSITION_LATENCY_LIMIT		(10 * 1000)



static void do_dbs_timer(void *data);



struct cpu_dbs_info_s {

	cputime64_t prev_cpu_idle;

	cputime64_t prev_cpu_wall;

	struct cpufreq_policy *cur_policy;

	unsigned int prev_cpu_idle_up;

	unsigned int prev_cpu_idle_down;

	unsigned int enable;

};

static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
@@ -87,24 +85,26 @@ static struct workqueue_struct *dbs_workq; 


struct dbs_tuners {

	unsigned int sampling_rate;

	unsigned int sampling_down_factor;

	unsigned int up_threshold;

	unsigned int ignore_nice;

};



static struct dbs_tuners dbs_tuners_ins = {

	.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,

	.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,

	.ignore_nice = 0,

};



static inline unsigned int get_cpu_idle_time(unsigned int cpu)

static inline cputime64_t get_cpu_idle_time(unsigned int cpu)

{

	return	kstat_cpu(cpu).cpustat.idle +

		kstat_cpu(cpu).cpustat.iowait +

		( dbs_tuners_ins.ignore_nice ?

		  kstat_cpu(cpu).cpustat.nice :

		  0);

	cputime64_t retval;



	retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,

			kstat_cpu(cpu).cpustat.iowait);



	if (dbs_tuners_ins.ignore_nice)

		retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);



	return retval;

}



/************************** sysfs interface ************************/
@@ -133,29 +133,9 @@ static ssize_t show_##file_name \ 
	return sprintf(buf, "%u\n", dbs_tuners_ins.object);		\

}

show_one(sampling_rate, sampling_rate);

show_one(sampling_down_factor, sampling_down_factor);

show_one(up_threshold, up_threshold);

show_one(ignore_nice_load, ignore_nice);



static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,

		const char *buf, size_t count)

{

	unsigned int input;

	int ret;

	ret = sscanf (buf, "%u", &input);

	if (ret != 1 )

		return -EINVAL;



	if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)

		return -EINVAL;



	mutex_lock(&dbs_mutex);

	dbs_tuners_ins.sampling_down_factor = input;

	mutex_unlock(&dbs_mutex);



	return count;

}



static ssize_t store_sampling_rate(struct cpufreq_policy *unused,

		const char *buf, size_t count)

{
@@ -217,12 +197,12 @@ static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy, 
	}

	dbs_tuners_ins.ignore_nice = input;



	/* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */

	/* we need to re-evaluate prev_cpu_idle */

	for_each_online_cpu(j) {

		struct cpu_dbs_info_s *j_dbs_info;

		j_dbs_info = &per_cpu(cpu_dbs_info, j);

		j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);

		j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;

		struct cpu_dbs_info_s *dbs_info;

		dbs_info = &per_cpu(cpu_dbs_info, j);

		dbs_info->prev_cpu_idle = get_cpu_idle_time(j);

		dbs_info->prev_cpu_wall = get_jiffies_64();

	}

	mutex_unlock(&dbs_mutex);
@@ -234,7 +214,6 @@ static struct freq_attr _name = \ 
__ATTR(_name, 0644, show_##_name, store_##_name)



define_one_rw(sampling_rate);

define_one_rw(sampling_down_factor);

define_one_rw(up_threshold);

define_one_rw(ignore_nice_load);
@@ -242,7 +221,6 @@ static struct attribute * dbs_attributes[] = { 
	&sampling_rate_max.attr,

	&sampling_rate_min.attr,

	&sampling_rate.attr,

	&sampling_down_factor.attr,

	&up_threshold.attr,

	&ignore_nice_load.attr,

	NULL
@@ -257,11 +235,10 @@ static struct attribute_group dbs_attr_group = { 


static void dbs_check_cpu(int cpu)

{

	unsigned int idle_ticks, up_idle_ticks, total_ticks;

	unsigned int freq_next;

	unsigned int freq_down_sampling_rate;

	static int down_skip[NR_CPUS];

	unsigned int idle_ticks, total_ticks;

	unsigned int load;

	struct cpu_dbs_info_s *this_dbs_info;

	cputime64_t cur_jiffies;



	struct cpufreq_policy *policy;

	unsigned int j;
@@ -271,10 +248,14 @@ static void dbs_check_cpu(int cpu) 
		return;



	policy = this_dbs_info->cur_policy;

	cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());

	total_ticks = (unsigned int) cputime64_sub(cur_jiffies,

			this_dbs_info->prev_cpu_wall);

	this_dbs_info->prev_cpu_wall = cur_jiffies;

	/*

	 * Every sampling_rate, we check, if current idle time is less

	 * than 20% (default), then we try to increase frequency

	 * Every sampling_rate*sampling_down_factor, we look for a the lowest

	 * Every sampling_rate, we look for a the lowest

	 * frequency which can sustain the load while keeping idle time over

	 * 30%. If such a frequency exist, we try to decrease to this frequency.

	 *
@@ -283,36 +264,26 @@ static void dbs_check_cpu(int cpu) 
	 * 5% (default) of current frequency

	 */



	/* Check for frequency increase */

	/* Get Idle Time */

	idle_ticks = UINT_MAX;

	for_each_cpu_mask(j, policy->cpus) {

		unsigned int tmp_idle_ticks, total_idle_ticks;

		cputime64_t total_idle_ticks;

		unsigned int tmp_idle_ticks;

		struct cpu_dbs_info_s *j_dbs_info;



		j_dbs_info = &per_cpu(cpu_dbs_info, j);

		total_idle_ticks = get_cpu_idle_time(j);

		tmp_idle_ticks = total_idle_ticks -

			j_dbs_info->prev_cpu_idle_up;

		j_dbs_info->prev_cpu_idle_up = total_idle_ticks;

		tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,

				j_dbs_info->prev_cpu_idle);

		j_dbs_info->prev_cpu_idle = total_idle_ticks;



		if (tmp_idle_ticks < idle_ticks)

			idle_ticks = tmp_idle_ticks;

	}

	load = (100 * (total_ticks - idle_ticks)) / total_ticks;



	/* Scale idle ticks by 100 and compare with up and down ticks */

	idle_ticks *= 100;

	up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *

			usecs_to_jiffies(dbs_tuners_ins.sampling_rate);



	if (idle_ticks < up_idle_ticks) {

		down_skip[cpu] = 0;

		for_each_cpu_mask(j, policy->cpus) {

			struct cpu_dbs_info_s *j_dbs_info;



			j_dbs_info = &per_cpu(cpu_dbs_info, j);

			j_dbs_info->prev_cpu_idle_down =

					j_dbs_info->prev_cpu_idle_up;

		}

	/* Check for frequency increase */

	if (load > dbs_tuners_ins.up_threshold) {

		/* if we are already at full speed then break out early */

		if (policy->cur == policy->max)

			return;
@@ -323,51 +294,23 @@ static void dbs_check_cpu(int cpu) 
	}



	/* Check for frequency decrease */

	down_skip[cpu]++;

	if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)

		return;



	idle_ticks = UINT_MAX;

	for_each_cpu_mask(j, policy->cpus) {

		unsigned int tmp_idle_ticks, total_idle_ticks;

		struct cpu_dbs_info_s *j_dbs_info;



		j_dbs_info = &per_cpu(cpu_dbs_info, j);

		/* Check for frequency decrease */

		total_idle_ticks = j_dbs_info->prev_cpu_idle_up;

		tmp_idle_ticks = total_idle_ticks -

			j_dbs_info->prev_cpu_idle_down;

		j_dbs_info->prev_cpu_idle_down = total_idle_ticks;



		if (tmp_idle_ticks < idle_ticks)

			idle_ticks = tmp_idle_ticks;

	}



	down_skip[cpu] = 0;

	/* if we cannot reduce the frequency anymore, break out early */

	if (policy->cur == policy->min)

		return;



	/* Compute how many ticks there are between two measurements */

	freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *

		dbs_tuners_ins.sampling_down_factor;

	total_ticks = usecs_to_jiffies(freq_down_sampling_rate);



	/*

	 * The optimal frequency is the frequency that is the lowest that

	 * can support the current CPU usage without triggering the up

	 * policy. To be safe, we focus 10 points under the threshold.

	 */

	freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;

	freq_next = (freq_next * policy->cur) /

	if (load < (dbs_tuners_ins.up_threshold - 10)) {

		unsigned int freq_next;

		freq_next = (policy->cur * load) /

			(dbs_tuners_ins.up_threshold - 10);



	if (freq_next < policy->min)

		freq_next = policy->min;



	if (freq_next <= ((policy->cur * 95) / 100))

		__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);

	}

}



static void do_dbs_timer(void *data)

{
@@ -432,9 +375,8 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
			j_dbs_info = &per_cpu(cpu_dbs_info, j);

			j_dbs_info->cur_policy = policy;



			j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);

			j_dbs_info->prev_cpu_idle_down

				= j_dbs_info->prev_cpu_idle_up;

			j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);

			j_dbs_info->prev_cpu_wall = get_jiffies_64();

		}

		this_dbs_info->enable = 1;

		sysfs_create_group(&policy->kobj, &dbs_attr_group);

include/asm-generic/cputime.h

+2 −0
Original line number Diff line number Diff line
@@ -24,7 +24,9 @@ typedef u64 cputime64_t; 


#define cputime64_zero (0ULL)

#define cputime64_add(__a, __b)		((__a) + (__b))

#define cputime64_sub(__a, __b)		((__a) - (__b))

#define cputime64_to_jiffies64(__ct)	(__ct)

#define jiffies64_to_cputime64(__jif)	(__jif)

#define cputime_to_cputime64(__ct)	((u64) __ct)