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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: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2019-02-27 10:27:58 +01:00 committed by Ingo Molnar
parent 602447f954
commit 8dc2d993cf
1 changed files with 3 additions and 2 deletions
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5
kernel/sched/fair.c
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@ -6189,6 +6189,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
u64 time, cost; u64 time, cost;
s64 delta; s64 delta;
int cpu, nr = INT_MAX; int cpu, nr = INT_MAX;
int this = smp_processor_id();
this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
if (!this_sd) if (!this_sd)
@ -6212,7 +6213,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
nr = 4; nr = 4;
} }
time = local_clock(); time = cpu_clock(this);
for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
if (!--nr) if (!--nr)
@ -6223,7 +6224,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
break; break;
} }
time = local_clock() - time; time = cpu_clock(this) - time;
cost = this_sd->avg_scan_cost; cost = this_sd->avg_scan_cost;
delta = (s64)(time - cost) / 8; delta = (s64)(time - cost) / 8;
this_sd->avg_scan_cost += delta; this_sd->avg_scan_cost += delta;