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Commit f8b27656 authored by Patrick Cain's avatar Patrick Cain
Browse files

cpufreq: Sync on thread migration optimizations 



When threads migrate between CPUs the destination CPU will temporarily
have a boosted frequency and the source CPU will have a residual higher
frequency even though the load could have just been reduced. To avoid
leaving CPUs at a high frequencies notify the source CPU after a thread
migration and make the interactive governor's timer reschedule
conditionally.

Change-Id: Id55055f2a116ca7ffd2a34dc3d0ec519c888a111
Signed-off-by: default avatarPatrick Cain <pcain@codeaurora.org>
parent 2d5582ac

drivers/cpufreq/cpu-boost.c

+11 −0
Original line number Diff line number Diff line
@@ -173,6 +173,17 @@ static int boost_mig_sync_thread(void *data) 


		/* Force policy re-evaluation to trigger adjust notifier. */

		get_online_cpus();

		if (cpu_online(src_cpu))

			/*

			 * Send an unchanged policy update to the source

			 * CPU. Even though the policy isn't changed from

			 * its existing boosted or non-boosted state

			 * notifying the source CPU will let the governor

			 * know a boost happened on another CPU and that it

			 * should re-evaluate the frequency at the next timer

			 * event without interference from a min sample time.

			 */

			cpufreq_update_policy(src_cpu);

		if (cpu_online(dest_cpu)) {

			cpufreq_update_policy(dest_cpu);

			queue_delayed_work_on(dest_cpu, cpu_boost_wq,

drivers/cpufreq/cpufreq_interactive.c

+46 −12
Original line number Diff line number Diff line
@@ -55,8 +55,11 @@ struct cpufreq_interactive_cpuinfo { 
	struct rw_semaphore enable_sem;

	int governor_enabled;

	int prev_load;

	bool limits_changed;

};



#define MIN_TIMER_JIFFIES 1UL



static DEFINE_PER_CPU(struct cpufreq_interactive_cpuinfo, cpuinfo);



/* realtime thread handles frequency scaling */
@@ -174,11 +177,15 @@ static void cpufreq_interactive_timer_resched( 
 * The cpu_timer and cpu_slack_timer must be deactivated when calling this

 * function.

 */

static void cpufreq_interactive_timer_start(int cpu)

static void cpufreq_interactive_timer_start(int cpu, int time_override)

{

	struct cpufreq_interactive_cpuinfo *pcpu = &per_cpu(cpuinfo, cpu);

	unsigned long expires = jiffies + usecs_to_jiffies(timer_rate);

	unsigned long flags;

	unsigned long expires;

	if (time_override)

		expires = jiffies + time_override;

	else

		expires = jiffies + usecs_to_jiffies(timer_rate);



	pcpu->cpu_timer.expires = expires;

	add_timer_on(&pcpu->cpu_timer, cpu);
@@ -448,6 +455,10 @@ static void cpufreq_interactive_timer(unsigned long data) 
	else

		mod_min_sample_time = min_sample_time;



	if (pcpu->limits_changed) {

		mod_min_sample_time = 0;

		pcpu->limits_changed = false;

	}

	if (new_freq < pcpu->floor_freq) {

		if (now - pcpu->floor_validate_time < mod_min_sample_time) {

			trace_cpufreq_interactive_notyet(
@@ -1192,6 +1203,7 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy, 
	unsigned int j;

	struct cpufreq_interactive_cpuinfo *pcpu;

	struct cpufreq_frequency_table *freq_table;

	unsigned long expire_time;



	switch (event) {

	case CPUFREQ_GOV_START:
@@ -1218,7 +1230,7 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy, 
			down_write(&pcpu->enable_sem);

			del_timer_sync(&pcpu->cpu_timer);

			del_timer_sync(&pcpu->cpu_slack_timer);

			cpufreq_interactive_timer_start(j);

			cpufreq_interactive_timer_start(j, 0);

			pcpu->governor_enabled = 1;

			up_write(&pcpu->enable_sem);

		}
@@ -1296,18 +1308,40 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy, 
			/* update target_freq firstly */

			if (policy->max < pcpu->target_freq)

				pcpu->target_freq = policy->max;

			else if (policy->min > pcpu->target_freq)

				pcpu->target_freq = policy->min;



			/* Reschedule timer.

			 * Delete the timers, else the timer callback may

			 * return without re-arm the timer when failed

			 * acquire the semaphore. This race may cause timer

			 * stopped unexpectedly.

			/*

			 * Delete and reschedule timer.

			 * Else the timer callback may return without

			 * re-arming the timer when it fails to acquire

			 * the semaphore. This race condition may cause the

			 * timer to stop unexpectedly.

			 */

			del_timer_sync(&pcpu->cpu_timer);

			del_timer_sync(&pcpu->cpu_slack_timer);

			cpufreq_interactive_timer_start(j);

			if (policy->min >= pcpu->target_freq) {

				pcpu->target_freq = policy->min;

				/*

				 * Reschedule timer.

				 * The governor needs more time to evaluate

				 * the load after changing policy parameters.

				 */

				cpufreq_interactive_timer_start(j, 0);

			} else {

				/*

				 * Reschedule timer with variable duration.

				 * No boost was applied so the governor

				 * doesn't need extra time to evaluate load.

				 * The timer can be set to fire quicker if it

				 * was already going to expire soon.

				 */

				expire_time = pcpu->cpu_timer.expires - jiffies;

				expire_time = min(usecs_to_jiffies(timer_rate),

						  expire_time);

				expire_time = max(MIN_TIMER_JIFFIES,

						  expire_time);



				cpufreq_interactive_timer_start(j, expire_time);

			}

			pcpu->limits_changed = true;

			up_write(&pcpu->enable_sem);

		}

		break;