Re: [PATCH v1 1/6] timer: make __next_timer_interrupt explicit aboutno future event

[Frederic Weisbecker]

2012/5/4 Frederic Weisbecker <fweisbec@xxxxxxxxx>:
> On Thu, May 03, 2012 at 05:55:57PM +0300, Gilad Ben-Yossef wrote:
>> @@ -1317,9 +1322,15 @@ unsigned long get_next_timer_interrupt(unsigned long now)
>>       if (cpu_is_offline(smp_processor_id()))
>>               return now + NEXT_TIMER_MAX_DELTA;
>>       spin_lock(&base->lock);
>> -     if (time_before_eq(base->next_timer, base->timer_jiffies))
>> -             base->next_timer = __next_timer_interrupt(base);
>> -     expires = base->next_timer;
>> +     if (time_before_eq(base->next_timer, base->timer_jiffies)) {
>> +
>> +             if (__next_timer_interrupt(base, &expires))
>> +                     base->next_timer = expires;
>> +             else
>> +                     expires = now + NEXT_TIMER_MAX_DELTA;
>
> I believe you can update base->next_timer to now + NEXT_TIMER_MAX_DELTA,
> so on any further idle interrupt exit that call tick_nohz_stop_sched_tick(),
> we won't get again the overhead of __next_timer_interrupt().

Ah forget that, I was confused. If we do that we actually get the useless timer
at now + NEXT_TIMER_MAX_DELTA.

So I think the patch is fine.

Acked-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
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