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sched: Revert nohz_ratelimit() for now

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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>
This commit is contained in:
Peter Zijlstra 2010-07-09 15:12:27 +02:00 committed by Ingo Molnar
parent f469461df6
commit 396e894d28
3 changed files with 1 additions and 17 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

6
include/linux/sched.h
View file

@ -273,17 +273,11 @@ extern cpumask_var_t nohz_cpu_mask;
#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ) #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ)
extern int select_nohz_load_balancer(int cpu); extern int select_nohz_load_balancer(int cpu);
extern int get_nohz_load_balancer(void); extern int get_nohz_load_balancer(void);
extern int nohz_ratelimit(int cpu);
#else #else
static inline int select_nohz_load_balancer(int cpu) static inline int select_nohz_load_balancer(int cpu)
{ {
return 0; return 0;
} }
static inline int nohz_ratelimit(int cpu)
{
return 0;
}
#endif #endif
/* /*

10
kernel/sched.c
View file

@ -1232,16 +1232,6 @@ void wake_up_idle_cpu(int cpu)
smp_send_reschedule(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 */ #endif /* CONFIG_NO_HZ */
static u64 sched_avg_period(void) static u64 sched_avg_period(void)

2
kernel/time/tick-sched.c
View file

@ -325,7 +325,7 @@ void tick_nohz_stop_sched_tick(int inidle)
} while (read_seqretry(&xtime_lock, seq)); } while (read_seqretry(&xtime_lock, seq));
if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || 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; next_jiffies = last_jiffies + 1;
delta_jiffies = 1; delta_jiffies = 1;
} else { } else {