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Commit 8dc2d993 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

x86/percpu, sched/fair: Avoid local_clock() 



Nadav reported that code-gen changed because of the this_cpu_*()
constraints, avoid this for select_idle_cpu() because that runs with
preemption (and IRQs) disabled anyway.

Reported-by: default avatarNadav Amit <nadav.amit@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 602447f9

kernel/sched/fair.c

+3 −2
Original line number Diff line number Diff line
@@ -6189,6 +6189,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t 
	u64 time, cost;

	s64 delta;

	int cpu, nr = INT_MAX;

	int this = smp_processor_id();



	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));

	if (!this_sd)
@@ -6212,7 +6213,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t 
			nr = 4;

	}



	time = local_clock();

	time = cpu_clock(this);



	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {

		if (!--nr)
@@ -6223,7 +6224,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t 
			break;

	}



	time = local_clock() - time;

	time = cpu_clock(this) - time;

	cost = this_sd->avg_scan_cost;

	delta = (s64)(time - cost) / 8;

	this_sd->avg_scan_cost += delta;