在 2013-8-6，下午3:29，Mike Galbraith <bitbuc...@online.de> 写道：
> +int sched_needs_cpu(int cpu)
> +{
> + return cpu_rq(cpu)->avg_idle < sysctl_sched_migration_cost;
> +}
> +
> #else /* CONFIG_NO_HZ_COMMON */
>
> static inline bool got_nohz_idle_kick(void)
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -548,7 +548,7 @@ static ktime_t tick_nohz_stop_sched_tick
> time_delta = timekeeping_max_deferment();
> } while (read_seqretry(&jiffies_lock, seq));
>
> - if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
> + if (sched_needs_cpu(cpu) || rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
> arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
> next_jiffies = last_jiffies + 1;
> delta_jiffies = 1;
If the performace regression was caused by too much expensive clock device
reprogramming and too frequent entering /exiting of C-states… this patch
should work.
except the following result is almost always false under 3.11-rc3 code.
> return cpu_rq(cpu)->avg_idle < sysctl_sched_migration_cost;
Ethan
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