diff options
| -rw-r--r-- | include/linux/tick.h | 2 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 52 |
2 files changed, 30 insertions, 24 deletions
diff --git a/include/linux/tick.h b/include/linux/tick.h index 8dc082194b22..d2ae79e21be3 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -43,6 +43,7 @@ enum tick_nohz_mode { * @idle_exittime: Time when the idle state was left * @idle_sleeptime: Sum of the time slept in idle with sched tick stopped * @sleep_length: Duration of the current idle sleep + * @do_timer_lst: CPU was the last one doing do_timer before going idle */ struct tick_sched { struct hrtimer sched_timer; @@ -64,6 +65,7 @@ struct tick_sched { unsigned long last_jiffies; unsigned long next_jiffies; ktime_t idle_expires; + int do_timer_last; }; extern void __init tick_init(void); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index a80b4644fe6b..df133bc29f89 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -263,17 +263,7 @@ void tick_nohz_stop_sched_tick(int inidle) seq = read_seqbegin(&xtime_lock); last_update = last_jiffies_update; last_jiffies = jiffies; - - /* - * On SMP we really should only care for the CPU which - * has the do_timer duty assigned. All other CPUs can - * sleep as long as they want. - */ - if (cpu == tick_do_timer_cpu || - tick_do_timer_cpu == TICK_DO_TIMER_NONE) - time_delta = timekeeping_max_deferment(); - else - time_delta = KTIME_MAX; + time_delta = timekeeping_max_deferment(); } while (read_seqretry(&xtime_lock, seq)); if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || @@ -296,6 +286,29 @@ void tick_nohz_stop_sched_tick(int inidle) if ((long)delta_jiffies >= 1) { /* + * If this cpu is the one which updates jiffies, then + * give up the assignment and let it be taken by the + * cpu which runs the tick timer next, which might be + * this cpu as well. If we don't drop this here the + * jiffies might be stale and do_timer() never + * invoked. Keep track of the fact that it was the one + * which had the do_timer() duty last. If this cpu is + * the one which had the do_timer() duty last, we + * limit the sleep time to the timekeeping + * max_deferement value which we retrieved + * above. Otherwise we can sleep as long as we want. + */ + if (cpu == tick_do_timer_cpu) { + tick_do_timer_cpu = TICK_DO_TIMER_NONE; + ts->do_timer_last = 1; + } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { + time_delta = KTIME_MAX; + ts->do_timer_last = 0; + } else if (!ts->do_timer_last) { + time_delta = KTIME_MAX; + } + + /* * calculate the expiry time for the next timer wheel * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals * that there is no timer pending or at least extremely @@ -312,21 +325,12 @@ void tick_nohz_stop_sched_tick(int inidle) */ time_delta = min_t(u64, time_delta, tick_period.tv64 * delta_jiffies); - expires = ktime_add_ns(last_update, time_delta); - } else { - expires.tv64 = KTIME_MAX; } - /* - * If this cpu is the one which updates jiffies, then - * give up the assignment and let it be taken by the - * cpu which runs the tick timer next, which might be - * this cpu as well. If we don't drop this here the - * jiffies might be stale and do_timer() never - * invoked. - */ - if (cpu == tick_do_timer_cpu) - tick_do_timer_cpu = TICK_DO_TIMER_NONE; + if (time_delta < KTIME_MAX) + expires = ktime_add_ns(last_update, time_delta); + else + expires.tv64 = KTIME_MAX; if (delta_jiffies > 1) cpumask_set_cpu(cpu, nohz_cpu_mask); |