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Commit 80800913 authored by venkatesh.pallipadi@intel.com's avatar venkatesh.pallipadi@intel.com Committed by Dave Jones
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[CPUFREQ][6/6] cpufreq: Add idle microaccounting in ondemand governor 



Use get_cpu_idle_time_us() to get micro-accounted idle information.
This enables ondemand to get more accurate idle and busy timings
than the jiffy based calculation. As a result, we can decrease
the ondemand safety gaurd band from 80-10 to 95-3.

Results in more aggressive power savings.

Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarDave Jones <davej@redhat.com>
parent 8083e4ad

drivers/cpufreq/cpufreq_ondemand.c

+44 −1
Original line number Diff line number Diff line
@@ -18,6 +18,9 @@ 
#include <linux/jiffies.h>

#include <linux/kernel_stat.h>

#include <linux/mutex.h>

#include <linux/hrtimer.h>

#include <linux/tick.h>

#include <linux/ktime.h>



/*

 * dbs is used in this file as a shortform for demandbased switching
@@ -26,6 +29,8 @@ 


#define DEF_FREQUENCY_DOWN_DIFFERENTIAL		(10)

#define DEF_FREQUENCY_UP_THRESHOLD		(80)

#define MICRO_FREQUENCY_DOWN_DIFFERENTIAL	(3)

#define MICRO_FREQUENCY_UP_THRESHOLD		(95)

#define MIN_FREQUENCY_UP_THRESHOLD		(11)

#define MAX_FREQUENCY_UP_THRESHOLD		(100)
@@ -58,6 +63,7 @@ enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE}; 
struct cpu_dbs_info_s {

	cputime64_t prev_cpu_idle;

	cputime64_t prev_cpu_wall;

	cputime64_t prev_cpu_nice;

	struct cpufreq_policy *cur_policy;

 	struct delayed_work work;

	struct cpufreq_frequency_table *freq_table;
@@ -97,7 +103,8 @@ static struct dbs_tuners { 
	.powersave_bias = 0,

};



static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)

static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu,

							cputime64_t *wall)

{

	cputime64_t idle_time;

	cputime64_t cur_wall_time;
@@ -123,6 +130,33 @@ static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall) 
	return idle_time;

}



static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)

{

	u64 idle_time = get_cpu_idle_time_us(cpu, wall);



	if (idle_time == -1ULL)

		return get_cpu_idle_time_jiffy(cpu, wall);



	if (dbs_tuners_ins.ignore_nice) {

		cputime64_t cur_nice;

		unsigned long cur_nice_jiffies;

		struct cpu_dbs_info_s *dbs_info;



		dbs_info = &per_cpu(cpu_dbs_info, cpu);

		cur_nice = cputime64_sub(kstat_cpu(cpu).cpustat.nice,

					 dbs_info->prev_cpu_nice);

		/*

		 * Assumption: nice time between sampling periods will be

		 * less than 2^32 jiffies for 32 bit sys

		 */

		cur_nice_jiffies = (unsigned long)

					cputime64_to_jiffies64(cur_nice);

		dbs_info->prev_cpu_nice = kstat_cpu(cpu).cpustat.nice;

		return idle_time + jiffies_to_usecs(cur_nice_jiffies);

	}

	return idle_time;

}



/*

 * Find right freq to be set now with powersave_bias on.

 * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
@@ -603,6 +637,15 @@ EXPORT_SYMBOL(cpufreq_gov_ondemand); 
static int __init cpufreq_gov_dbs_init(void)

{

	int err;

	cputime64_t wall;

	u64 idle_time = get_cpu_idle_time_us(smp_processor_id(), &wall);



	if (idle_time != -1ULL) {

		/* Idle micro accounting is supported. Use finer thresholds */

		dbs_tuners_ins.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;

		dbs_tuners_ins.down_differential =

					MICRO_FREQUENCY_DOWN_DIFFERENTIAL;

	}



	kondemand_wq = create_workqueue("kondemand");

	if (!kondemand_wq) {