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Commit 188a83c4 authored by Joonwoo Park's avatar Joonwoo Park
Browse files

sched/rt: make RT task placement to be C-state aware 



Make RT task placement to take C-state into consideration to reduce
wake-up latency.

Change-Id: I06aff72825a503413944274f456b91f5139081e7
Signed-off-by: default avatarJoonwoo Park <joonwoop@codeaurora.org>
parent 0b6cfb36

kernel/sched/rt.c

+36 −11
Original line number Diff line number Diff line
@@ -1725,6 +1725,8 @@ static int find_lowest_rq(struct task_struct *task) 
	unsigned long best_capacity;

	unsigned long util, best_cpu_util = ULONG_MAX;

	unsigned long tutil = task_util(task);

	int best_cpu_idle_idx = INT_MAX;

	int cpu_idle_idx = -1;

	bool placement_boost;



	/* Make sure the mask is initialized first */
@@ -1787,21 +1789,44 @@ static int find_lowest_rq(struct task_struct *task) 
			 * double count rt task load.

			 */

			util = cpu_util(cpu);

			if (!__cpu_overutilized(cpu, util + tutil)) {



			if (__cpu_overutilized(cpu, util + tutil))

				continue;



			if (cpu_isolated(cpu))

				continue;



			if (sched_cpu_high_irqload(cpu))

				continue;



				if (best_cpu_util > util ||

				    (best_cpu_util == util &&

				     cpu == task_cpu(task))) {

			/* Find the least loaded CPU */

			if (util > best_cpu_util)

				continue;



			/*

			 * If the previous CPU has same load, keep it as

			 * best_cpu.

			 */

			if (best_cpu_util == util && best_cpu == task_cpu(task))

				continue;



			/*

			 * If candidate CPU is the previous CPU, select it.

			 * Otherwise, if its load is same with best_cpu and in

			 * a shallower C-state, select it.

			 */

			cpu_idle_idx = idle_get_state_idx(cpu_rq(cpu));

			if (cpu != task_cpu(task) &&

			    sysctl_sched_cstate_aware) {

				if (best_cpu_util == util &&

				    best_cpu_idle_idx < cpu_idle_idx)

					continue;

			}



			best_cpu_idle_idx = cpu_idle_idx;

			best_cpu_util = util;

			best_cpu = cpu;

		}

			}

		}



		if (best_cpu != -1) {

			return best_cpu;