[tip:sched/urgent] sched: Revert nohz_ratelimit() for now

tip-bot for Peter Zijlstra
2010-07-17T11:13:18Z

Commit-ID: 396e894d289d69bacf5acd983c97cd6e21a14c08
Gitweb: http://git.kernel.org/tip/396e894d289d69bacf5acd983c97cd6e21a14c08
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 9 Jul 2010 15:12:27 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 17 Jul 2010 12:05:44 +0200

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>
---
include/linux/sched.h | 6 ------
kernel/sched.c | 10 ----------
kernel/time/tick-sched.c | 2 +-
3 files changed, 1 insertions(+), 17 deletions(-)

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 {