Commit 7a82e5f5 authored by Vincent Guittot's avatar Vincent Guittot Committed by Ingo Molnar
Browse files

sched/fair: Merge for each idle cpu loop of ILB 



Remove the specific case for handling this_cpu outside for_each_cpu() loop
when running ILB. Instead we use for_each_cpu_wrap() and start with the
next cpu after this_cpu so we will continue to finish with this_cpu.

update_nohz_stats() is now used for this_cpu too and will prevents
unnecessary update. We don't need a special case for handling the update of
nohz.next_balance for this_cpu anymore because it is now handled by the
loop like others.

Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224133007.28644-5-vincent.guittot@linaro.org
parent 64f84f27

kernel/sched/fair.c

+7 −25
Original line number Diff line number Diff line
@@ -10043,22 +10043,9 @@ static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) 
	 * When the cpu is attached to null domain for ex, it will not be

	 * updated.

	 */

	if (likely(update_next_balance)) {

	if (likely(update_next_balance))

		rq->next_balance = next_balance;



#ifdef CONFIG_NO_HZ_COMMON

		/*

		 * If this CPU has been elected to perform the nohz idle

		 * balance. Other idle CPUs have already rebalanced with

		 * nohz_idle_balance() and nohz.next_balance has been

		 * updated accordingly. This CPU is now running the idle load

		 * balance for itself and we need to update the

		 * nohz.next_balance accordingly.

		 */

		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))

			nohz.next_balance = rq->next_balance;

#endif

	}

}



static inline int on_null_domain(struct rq *rq)
@@ -10385,8 +10372,12 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags, 
	 */

	smp_mb();



	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {

		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))

	/*

	 * Start with the next CPU after this_cpu so we will end with this_cpu and let a

	 * chance for other idle cpu to pull load.

	 */

	for_each_cpu_wrap(balance_cpu,  nohz.idle_cpus_mask, this_cpu+1) {

		if (!idle_cpu(balance_cpu))

			continue;



		/*
@@ -10432,15 +10423,6 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags, 
	if (likely(update_next_balance))

		nohz.next_balance = next_balance;



	/* Newly idle CPU doesn't need an update */

	if (idle != CPU_NEWLY_IDLE) {

		update_blocked_averages(this_cpu);

		has_blocked_load |= this_rq->has_blocked_load;

	}



	if (flags & NOHZ_BALANCE_KICK)

		rebalance_domains(this_rq, CPU_IDLE);



	WRITE_ONCE(nohz.next_blocked,

		now + msecs_to_jiffies(LOAD_AVG_PERIOD));