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Commit 9e293db0 authored by Joonwoo Park's avatar Joonwoo Park Committed by Todd Kjos
Browse files

sched: EAS: upmigrate misfit current task 



Upmigrate misfit current task upon scheduler tick with stopper.

We can kick an random (not necessarily big CPU) NOHZ idle CPU when a
CPU bound task is in need of upmigration.  But it's not efficient as that
way needs following unnecessary wakeups:

  1. Busy little CPU A to kick idle B
  2. B runs idle balancer and enqueue migration/A
  3. B goes idle
  4. A runs migration/A, enqueues busy task on B.
  5. B wakes up again.

This change makes active upmigration more efficiently by doing:

  1. Busy little CPU A find target CPU B upon tick.
  2. CPU A enqueues migration/A.

Change-Id: Ie865738054ea3296f28e6ba01710635efa7193c0
[joonwoop: The original version had logic to reserve CPU.  The logic is
 omitted in this version.]
Signed-off-by: default avatarJoonwoo Park <joonwoop@codeaurora.org>
Signed-off-by: default avatarVikram Mulukutla <markivx@codeaurora.org>
parent dc626b28

kernel/sched/core.c

+3 −0
Original line number Diff line number Diff line
@@ -3097,6 +3097,9 @@ void scheduler_tick(void) 
	trigger_load_balance(rq);

#endif

	rq_last_tick_reset(rq);



	if (curr->sched_class == &fair_sched_class)

		check_for_migration(rq, curr);

}



#ifdef CONFIG_NO_HZ_FULL

kernel/sched/fair.c

+46 −2
Original line number Diff line number Diff line
@@ -6312,7 +6312,9 @@ done: 


/*

 * cpu_util_wake: Compute cpu utilization with any contributions from

 * the waking task p removed.

 * the waking task p removed.  check_for_migration() looks for a better CPU of

 * rq->curr. For that case we should return cpu util with contributions from

 * currently running task p removed.

 */

static int cpu_util_wake(int cpu, struct task_struct *p)

{
@@ -6325,7 +6327,8 @@ static int cpu_util_wake(int cpu, struct task_struct *p) 
	 * utilization from cpu utilization. Instead just use

	 * cpu_util for this case.

	 */

	if (!walt_disabled && sysctl_sched_use_walt_cpu_util)

	if (!walt_disabled && sysctl_sched_use_walt_cpu_util &&

	    p->state == TASK_WAKING)

		return cpu_util(cpu);

#endif

	/* Task has no contribution or is new */
@@ -9974,6 +9977,47 @@ static void rq_offline_fair(struct rq *rq) 
	unthrottle_offline_cfs_rqs(rq);

}



static inline int

kick_active_balance(struct rq *rq, struct task_struct *p, int new_cpu)

{

	int rc = 0;



	/* Invoke active balance to force migrate currently running task */

	raw_spin_lock(&rq->lock);

	if (!rq->active_balance) {

		rq->active_balance = 1;

		rq->push_cpu = new_cpu;

		get_task_struct(p);

		rq->push_task = p;

		rc = 1;

	}

	raw_spin_unlock(&rq->lock);



	return rc;

}



void check_for_migration(struct rq *rq, struct task_struct *p)

{

	int new_cpu;

	int active_balance;

	int cpu = task_cpu(p);



	if (rq->misfit_task) {

		if (rq->curr->state != TASK_RUNNING ||

		    rq->curr->nr_cpus_allowed == 1)

			return;



		new_cpu = select_energy_cpu_brute(p, cpu, 0);

		if (capacity_orig_of(new_cpu) > capacity_orig_of(cpu)) {

			active_balance = kick_active_balance(rq, p, new_cpu);

			if (active_balance)

				stop_one_cpu_nowait(cpu,

						active_load_balance_cpu_stop,

						rq, &rq->active_balance_work);

		}

	}

}



#endif /* CONFIG_SMP */



/*

kernel/sched/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -31,8 +31,10 @@ extern long calc_load_fold_active(struct rq *this_rq); 


#ifdef CONFIG_SMP

extern void update_cpu_load_active(struct rq *this_rq);

extern void check_for_migration(struct rq *rq, struct task_struct *p);

#else

static inline void update_cpu_load_active(struct rq *this_rq) { }

static inline void check_for_migration(struct rq *rq, struct task_struct *p) { }

#endif



/*