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Commit b6ea56e9 authored by Pavankumar Kondeti's avatar Pavankumar Kondeti Committed by Matt Wagantall
Browse files

sched: auto adjust the upmigrate and downmigrate thresholds 



The load scale factor of a CPU gets boosted when its max freq
is restricted. A task load at the same frequency is scaled higher
than normal under this scenario. This results in tasks migrating
early to the better capacity CPUs and their residency over there
also gets increased as their inflated load would be relatively
higher than than the downmigrate threshold.

Auto adjust the upmigrate and downmigrate thresholds by a factor
equal to  rq->max_possible_freq/rq->max_freq of a lower capacity CPU.
If the adjusted upmigrate threshold exceeds the window size, it is
clipped to the window size. If the adjusted downmigrate threshold
decreases the difference between the upmigrate and downmigrate, it is
clipped to a value such that the difference between the modified
and the original thresholds is same.

Change-Id: Ifa70ee5d4ca5fe02789093c7f070c77629907f04
Signed-off-by: default avatarPavankumar Kondeti <pkondeti@codeaurora.org>
parent a1f9ca13

Documentation/scheduler/sched-hmp.txt

+18 −0
Original line number Diff line number Diff line
@@ -570,6 +570,24 @@ both tasks and CPUs to aid in the placement of tasks. 
  whose upmigrate_discourage flag is set) will never be classified as big tasks

  despite their high demand.



  As the load scale factor is calculated against current fmax, it gets boosted

  when a lower capacity CPU is restricted to run at lower fmax. The task

  demand is inflated in this scenario and the task upmigrates early to the

  maximum capacity CPU. Hence this threshold is auto-adjusted by a factor

  equal to max_possible_frequency/current_frequency of a lower capacity CPU.

  This adjustment happens only when the lower capacity CPU frequency is

  restricted. The same adjustment is applied to the downmigrate threshold

  as well.



  When the frequency restriction is relaxed, the previous values are restored.

  sched_up_down_migrate_auto_update macro defined in kernel/sched/core.c

  controls this auto-adjustment behavior and it is enabled by default.



  If the adjusted upmigrate threshold exceeds the window size, it is clipped to

  the window size. If the adjusted downmigrate threshold decreases the difference

  between the upmigrate and downmigrate, it is clipped to a value such that the

  difference between the modified and the original thresholds is same.



- mostly_idle



  The "mostly_idle" classification applies to CPUs. This

kernel/sched/core.c

+22 −0
Original line number Diff line number Diff line
@@ -2408,6 +2408,27 @@ static int compute_load_scale_factor(int cpu) 
	return load_scale;

}



#define sched_up_down_migrate_auto_update 1

static void check_for_up_down_migrate_update(const struct cpumask *cpus)

{

	int i = cpumask_first(cpus);

	struct rq *rq = cpu_rq(i);



	if (!sched_up_down_migrate_auto_update)

		return;



	if (rq->max_possible_capacity == max_possible_capacity)

		return;



	if (rq->max_possible_freq == rq->max_freq)

		up_down_migrate_scale_factor = 1024;

	else

		up_down_migrate_scale_factor = (1024 * rq->max_possible_freq)/

					rq->max_freq;



	update_up_down_migrate();

}



static int cpufreq_notifier_policy(struct notifier_block *nb,

		unsigned long val, void *data)

{
@@ -2510,6 +2531,7 @@ static int cpufreq_notifier_policy(struct notifier_block *nb, 
	}



	__update_min_max_capacity();

	check_for_up_down_migrate_update(policy->related_cpus);

	post_big_small_task_count_change(cpu_possible_mask);



	return 0;

kernel/sched/fair.c

+38 −5
Original line number Diff line number Diff line
@@ -2541,6 +2541,14 @@ unsigned int __read_mostly sysctl_sched_downmigrate_pct = 60; 
static int __read_mostly sched_upmigrate_min_nice = 15;

int __read_mostly sysctl_sched_upmigrate_min_nice = 15;



/*

 * The load scale factor of a CPU gets boosted when its max frequency

 * is restricted due to which the tasks are migrating to higher capacity

 * CPUs early. The sched_upmigrate threshold is auto-upgraded by

 * rq->max_possible_freq/rq->max_freq of a lower capacity CPU.

 */

unsigned int up_down_migrate_scale_factor = 1024;



/*

 * Scheduler boost is a mechanism to temporarily place tasks on CPUs

 * with higher capacity than those where a task would have normally
@@ -2556,6 +2564,35 @@ static inline int available_cpu_capacity(int cpu) 
	return rq->capacity;

}



void update_up_down_migrate(void)

{

	unsigned int up_migrate = pct_to_real(sysctl_sched_upmigrate_pct);

	unsigned int down_migrate = pct_to_real(sysctl_sched_downmigrate_pct);

	unsigned int delta;



	if (up_down_migrate_scale_factor == 1024)

		goto done;



	delta = up_migrate - down_migrate;



	up_migrate /= NSEC_PER_USEC;

	up_migrate *= up_down_migrate_scale_factor;

	up_migrate >>= 10;

	up_migrate *= NSEC_PER_USEC;



	up_migrate = min(up_migrate, sched_ravg_window);



	down_migrate /= NSEC_PER_USEC;

	down_migrate *= up_down_migrate_scale_factor;

	down_migrate >>= 10;

	down_migrate *= NSEC_PER_USEC;



	down_migrate = min(down_migrate, up_migrate - delta);

done:

	sched_upmigrate = up_migrate;

	sched_downmigrate = down_migrate;

}



void set_hmp_defaults(void)

{

	sched_spill_load =
@@ -2564,11 +2601,7 @@ void set_hmp_defaults(void) 
	sched_small_task =

		pct_to_real(sysctl_sched_small_task_pct);



	sched_upmigrate =

		pct_to_real(sysctl_sched_upmigrate_pct);



	sched_downmigrate =

		pct_to_real(sysctl_sched_downmigrate_pct);

	update_up_down_migrate();



#ifdef CONFIG_SCHED_FREQ_INPUT

	sched_heavy_task =

kernel/sched/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -910,6 +910,7 @@ extern unsigned int sched_init_task_load_pelt; 
extern unsigned int sched_init_task_load_windows;

extern u64 scale_load_to_cpu(u64 load, int cpu);

extern unsigned int sched_heavy_task;

extern unsigned int up_down_migrate_scale_factor;

extern void reset_cpu_hmp_stats(int cpu, int reset_cra);

extern void fixup_nr_big_small_task(int cpu, int reset_stats);

extern unsigned int task_load(struct task_struct *p);
@@ -918,6 +919,7 @@ extern void sched_account_irqtime(int cpu, struct task_struct *curr, 
				 u64 delta, u64 wallclock);

unsigned int cpu_temp(int cpu);

extern unsigned int nr_eligible_big_tasks(int cpu);

extern void update_up_down_migrate(void);



static inline int capacity(struct rq *rq)

{