Merge "sched: Provide knob to prefer mostly_idle over idle cpus" (6c4998df) · Commits · e / devices / samsung / android_kernel_samsung_msm8916

include/linux/sched/sysctl.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -62,6 +62,7 @@ extern unsigned int sysctl_sched_small_task_pct;
		extern unsigned int sysctl_sched_upmigrate_pct;
		extern unsigned int sysctl_sched_downmigrate_pct;
		extern int sysctl_sched_upmigrate_min_nice;
		extern unsigned int sysctl_sched_prefer_idle;
		extern unsigned int sysctl_sched_powerband_limit_pct;
		extern unsigned int sysctl_sched_boost;

kernel/sched/fair.c

+53 −21

Original line number	Diff line number	Diff line
		@@ -1337,6 +1337,13 @@ unsigned int __read_mostly sysctl_sched_downmigrate_pct = 60;
		*/
		int __read_mostly sysctl_sched_upmigrate_min_nice = 15;

		/*
		* Tunable to govern scheduler wakeup placement CPU selection
		* preference. If set, the scheduler chooses to wake up a task
		* on an idle CPU.
		*/
		unsigned int __read_mostly sysctl_sched_prefer_idle;

		/*
		* Scheduler boost is a mechanism to temporarily place tasks on CPUs
		* with higher capacity than those where a task would have normally
		@@ -1766,9 +1773,10 @@ static int skip_cpu(struct task_struct *p, int cpu, int reason)
		/* return cheapest cpu that can fit this task */
		static int select_best_cpu(struct task_struct *p, int target, int reason)
		{
		int i, best_cpu = -1, fallback_idle_cpu = -1;
		int i, best_cpu = -1, fallback_idle_cpu = -1, min_cstate_cpu = -1;
		int prev_cpu = task_cpu(p);
		int cpu_cost, min_cost = INT_MAX;
		int min_idle_cost = INT_MAX, min_busy_cost = INT_MAX;
		u64 load, min_load = ULLONG_MAX, min_fallback_load = ULLONG_MAX;
		int small_task = is_small_task(p);
		int boost = sched_boost();
		@@ -1824,43 +1832,67 @@ static int select_best_cpu(struct task_struct *p, int target, int reason)
		* overrides load and C-state.
		*/
		if (power_delta_exceeded(cpu_cost, min_cost)) {
		if (cpu_cost < min_cost) {
		min_load = load;
		if (cpu_cost > min_cost)
		continue;

		min_cost = cpu_cost;
		min_load = ULLONG_MAX;
		min_cstate = INT_MAX;
		min_cstate_cpu = -1;
		best_cpu = -1;
		}

		/*
		* Partition CPUs based on whether they are completely idle
		* or not. For completely idle CPUs we choose the one in
		* the lowest C-state and then break ties with power cost
		*/
		if (idle_cpu(i)) {
		if (cstate > min_cstate)
		continue;

		if (cstate < min_cstate) {
		min_idle_cost = cpu_cost;
		min_cstate = cstate;
		best_cpu = i;
		min_cstate_cpu = i;
		continue;
		}

		if (cpu_cost < min_idle_cost) {
		min_idle_cost = cpu_cost;
		min_cstate_cpu = i;
		}
		continue;
		}

		/* After power band, load is prioritized next. */
		/*
		* For CPUs that are not completely idle, pick one with the
		* lowest load and break ties with power cost
		*/
		if (load > min_load)
		continue;

		if (load < min_load) {
		min_load = load;
		min_cost = cpu_cost;
		min_cstate = cstate;
		min_busy_cost = cpu_cost;
		best_cpu = i;
		continue;
		}
		if (load > min_load)
		continue;

		/*
		* The load is equal to the previous selected CPU.
		* This will most often occur when deciding between
		* idle CPUs. Power cost is prioritized after load,
		* followed by cstate.
		* This is rare but when it does happen opt for the
		* more power efficient CPU option.
		*/
		if (cpu_cost < min_cost) {
		min_cost = cpu_cost;
		min_cstate = cstate;
		best_cpu = i;
		continue;
		}
		if (cpu_cost == min_cost && cstate < min_cstate) {
		min_cstate = cstate;
		if (cpu_cost < min_busy_cost) {
		min_busy_cost = cpu_cost;
		best_cpu = i;
		}
		}

		if (min_cstate_cpu >= 0 && (sysctl_sched_prefer_idle \|\|
		!(best_cpu >= 0 && mostly_idle_cpu(best_cpu))))
		best_cpu = min_cstate_cpu;
		done:
		if (best_cpu < 0) {
		if (unlikely(fallback_idle_cpu < 0))

kernel/sysctl.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -416,6 +416,13 @@ static struct ctl_table kern_table[] = {
		.mode = 0644,
		.proc_handler = proc_dointvec,
		},
		{
		.procname = "sched_prefer_idle",
		.data = &sysctl_sched_prefer_idle,
		.maxlen = sizeof(unsigned int),
		.mode = 0644,
		.proc_handler = proc_dointvec,
		},
		{
		.procname = "sched_init_task_load",
		.data = &sysctl_sched_init_task_load_pct,