Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit bdecea3a authored by Siddha, Suresh B's avatar Siddha, Suresh B Committed by Linus Torvalds
Browse files

sched: fix idle load balancing in softirqd context 



Periodic load balancing in recent kernels happen in the softirq.  In
certain -rt configurations, these softirqs are handled in softirqd context.
 And hence the check for idle processor was always returning busy (as
nr_running > 1).

This patch captures the idle information at the tick and passes this info
to softirq context through an element 'idle_at_tick' in rq.

[kernel@kolivas.org: Fix reverse idle at tick logic]
Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2bd7e20e

kernel/sched.c

+5 −7
Original line number Diff line number Diff line
@@ -223,6 +223,7 @@ struct rq { 
	unsigned long raw_weighted_load;

#ifdef CONFIG_SMP

	unsigned long cpu_load[3];

	unsigned char idle_at_tick;

#endif

	unsigned long long nr_switches;
@@ -2943,12 +2944,7 @@ static void run_rebalance_domains(struct softirq_action *h) 
	struct rq *this_rq = cpu_rq(this_cpu);

	unsigned long interval;

	struct sched_domain *sd;

	/*

	 * We are idle if there are no processes running. This

	 * is valid even if we are the idle process (SMT).

	 */

	enum idle_type idle = !this_rq->nr_running ?

				SCHED_IDLE : NOT_IDLE;

	enum idle_type idle = this_rq->idle_at_tick ? SCHED_IDLE : NOT_IDLE;

	/* Earliest time when we have to call run_rebalance_domains again */

	unsigned long next_balance = jiffies + 60*HZ;
@@ -3218,14 +3214,16 @@ void scheduler_tick(void) 
	unsigned long long now = sched_clock();

	struct task_struct *p = current;

	int cpu = smp_processor_id();

	int idle_at_tick = idle_cpu(cpu);

	struct rq *rq = cpu_rq(cpu);



	update_cpu_clock(p, rq, now);



	if (p != rq->idle)

	if (!idle_at_tick)

		task_running_tick(rq, p);

#ifdef CONFIG_SMP

	update_load(rq);

	rq->idle_at_tick = idle_at_tick;

	if (time_after_eq(jiffies, rq->next_balance))

		raise_softirq(SCHED_SOFTIRQ);

#endif