From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Date: Fri, 9 Jul 2010 13:12:27 +0000 (+0200)

Subject: sched: Revert nohz_ratelimit() for now

X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Fx86%2Flinux-2.6-tip.git;a=commitdiff_plain;h=396e894d289d69bacf5acd983c97cd6e21a14c08

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>

---

diff --git a/include/linux/sched.h b/include/linux/sched.h

index 747fcae..6e0bb86 100644

--- a/include/linux/sched.h

+++ b/include/linux/sched.h

@@ -273,17 +273,11 @@ extern cpumask_var_t nohz_cpu_mask;

 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ)

 extern int select_nohz_load_balancer(int cpu);

 extern int get_nohz_load_balancer(void);

-extern int nohz_ratelimit(int cpu);

 #else

 static inline int select_nohz_load_balancer(int cpu)

 {

 	return 0;

 }

-

-static inline int nohz_ratelimit(int cpu)

-{

-	return 0;

-}

 #endif

 /*

diff --git a/kernel/sched.c b/kernel/sched.c

index f52a880..63b4a14 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 813993b..f898af6 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 {