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Commit 9c8a5a48 authored by Junjie Wu's avatar Junjie Wu
Browse files

cpufreq: interactive: Handle notification even if timer fires first 



Scheduler provides different load number based on whether a
notification is pending. Under normal situation, it won't provide a
load that exceeds 100% busy time of current frequency. For migration,
the busy time can be huge if a heavy task just moved to the CPU.

This creates a race condition due to how governor handles
notification:
1) Scheduler sends notification for a big task
2) Governor timer runs, and gets a huge load, but fails to skip
hispeed_freq logic and all delays because it's not a notification
3) After receiving sched_get_cpus_busy(), scheduler thinks governor has
finished handling the notification and changes to provide normal load
that is capped to 100% of the CPU at current frequency.
4) Governor now starts handling notification, but gets a small load
that doesn't reflect real demand of the heavy task.

The migration notification is thus effectively lost. Fixing this by
making notification pending a per-cpu flag. If timer gets ahead of
notification handling, it will be run as if it's a notification.

Change-Id: Ie3d68edf85b822232a646c2694bec6928a2d7cd1
Signed-off-by: default avatarJunjie Wu <junjiew@codeaurora.org>
parent 64182585

drivers/cpufreq/cpufreq_interactive.c

+14 −10
Original line number Original line Diff line number Diff line
@@ -51,6 +51,7 @@ struct cpufreq_interactive_policyinfo { 
	u64 max_freq_hyst_start_time;

	u64 max_freq_hyst_start_time;

	struct rw_semaphore enable_sem;

	struct rw_semaphore enable_sem;

	bool reject_notification;

	bool reject_notification;

	bool notif_pending;

	int governor_enabled;

	int governor_enabled;

	struct cpufreq_interactive_tunables *cached_tunables;

	struct cpufreq_interactive_tunables *cached_tunables;

	struct sched_load *sl;

	struct sched_load *sl;
@@ -433,7 +434,7 @@ static u64 update_load(int cpu) 
}

}





#define NEW_TASK_RATIO 75

#define NEW_TASK_RATIO 75

static void __cpufreq_interactive_timer(unsigned long data, bool is_notif)

static void cpufreq_interactive_timer(unsigned long data)

{

{

	u64 now;

	u64 now;

	unsigned int delta_time;

	unsigned int delta_time;
@@ -462,12 +463,15 @@ static void __cpufreq_interactive_timer(unsigned long data, bool is_notif) 
		goto exit;

		goto exit;





	fcpu = cpumask_first(ppol->policy->related_cpus);

	fcpu = cpumask_first(ppol->policy->related_cpus);

	skip_hispeed_logic = tunables->ignore_hispeed_on_notif && is_notif;

	skip_min_sample_time = tunables->fast_ramp_down && is_notif;



	now = ktime_to_us(ktime_get());

	now = ktime_to_us(ktime_get());



	spin_lock_irqsave(&ppol->target_freq_lock, flags);

	spin_lock_irqsave(&ppol->target_freq_lock, flags);

	spin_lock(&ppol->load_lock);

	spin_lock(&ppol->load_lock);



	skip_hispeed_logic = tunables->ignore_hispeed_on_notif &&

						ppol->notif_pending;

	skip_min_sample_time = tunables->fast_ramp_down && ppol->notif_pending;

	ppol->notif_pending = false;

	ppol->last_evaluated_jiffy = get_jiffies_64();

	ppol->last_evaluated_jiffy = get_jiffies_64();





	if (tunables->use_sched_load)

	if (tunables->use_sched_load)
@@ -649,11 +653,6 @@ exit: 
	return;

	return;

}

}





static void cpufreq_interactive_timer(unsigned long data)

{

	__cpufreq_interactive_timer(data, false);

}



static int cpufreq_interactive_speedchange_task(void *data)

static int cpufreq_interactive_speedchange_task(void *data)

{

{

	unsigned int cpu;

	unsigned int cpu;
@@ -752,6 +751,7 @@ static int load_change_callback(struct notifier_block *nb, unsigned long val, 
	unsigned long cpu = (unsigned long) data;

	unsigned long cpu = (unsigned long) data;

	struct cpufreq_interactive_policyinfo *ppol = per_cpu(polinfo, cpu);

	struct cpufreq_interactive_policyinfo *ppol = per_cpu(polinfo, cpu);

	struct cpufreq_interactive_tunables *tunables;

	struct cpufreq_interactive_tunables *tunables;

	unsigned long flags;





	if (speedchange_task == current)

	if (speedchange_task == current)

		return 0;

		return 0;
@@ -771,9 +771,12 @@ static int load_change_callback(struct notifier_block *nb, unsigned long val, 
	}

	}





	trace_cpufreq_interactive_load_change(cpu);

	trace_cpufreq_interactive_load_change(cpu);

	spin_lock_irqsave(&ppol->target_freq_lock, flags);

	ppol->notif_pending = true;

	spin_unlock_irqrestore(&ppol->target_freq_lock, flags);

	del_timer(&ppol->policy_timer);

	del_timer(&ppol->policy_timer);

	del_timer(&ppol->policy_slack_timer);

	del_timer(&ppol->policy_slack_timer);

	__cpufreq_interactive_timer(cpu, true);

	cpufreq_interactive_timer(cpu);





	up_read(&ppol->enable_sem);

	up_read(&ppol->enable_sem);

	return 0;

	return 0;
@@ -1695,6 +1698,7 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy, 
		ppol->hispeed_validate_time = ppol->floor_validate_time;

		ppol->hispeed_validate_time = ppol->floor_validate_time;

		ppol->min_freq = policy->min;

		ppol->min_freq = policy->min;

		ppol->reject_notification = true;

		ppol->reject_notification = true;

		ppol->notif_pending = false;

		down_write(&ppol->enable_sem);

		down_write(&ppol->enable_sem);

		del_timer_sync(&ppol->policy_timer);

		del_timer_sync(&ppol->policy_timer);

		del_timer_sync(&ppol->policy_slack_timer);

		del_timer_sync(&ppol->policy_slack_timer);