sched: Revert nohz_ratelimit() for now

Norbert reported that nohz_ratelimit() causes his laptop to burn about
4W (40%) extra. For now back out the change and see if we can adjust
the power management code to make better decisions.

Reported-by: Norbert Preining <preining@logic.at>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 1 insertions, 11 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index f52a8801b7a2..63b4a14682fa 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1232,16 +1232,6 @@ void wake_up_idle_cpu(int cpu)
                 smp_send_reschedule(cpu);
 }
 
-int nohz_ratelimit(int cpu)
-{
-        struct rq *rq = cpu_rq(cpu);
-        u64 diff = rq->clock - rq->nohz_stamp;
-
-        rq->nohz_stamp = rq->clock;
-
-        return diff < (NSEC_PER_SEC / HZ) >> 1;
-}
-
 #endif /* CONFIG_NO_HZ */
 
 static u64 sched_avg_period(void)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 813993b5fb61..f898af608171 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -325,7 +325,7 @@ void tick_nohz_stop_sched_tick(int inidle)
         } while (read_seqretry(&xtime_lock, seq));
 
         if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) ||
-            arch_needs_cpu(cpu) || nohz_ratelimit(cpu)) {
+            arch_needs_cpu(cpu)) {
                 next_jiffies = last_jiffies + 1;
                 delta_jiffies = 1;
         } else {