On 2020/12/15 22:47, Frederic Weisbecker wrote:
> On Tue, Dec 15, 2020 at 08:06:34PM +0800, Yunfeng Ye wrote:
>> The idle_exittime field of tick_sched is used to record the time when
>> the idle state was left. but currently the idle_exittime is updated in
>> the function tick_nohz_restart_sched_tick(), which is not always in idle
>> state when nohz_full is configured.
>>
>> tick_irq_exit
>> tick_nohz_irq_exit
>> tick_nohz_full_update_tick
>> tick_nohz_restart_sched_tick
>> ts->idle_exittime = now;
>>
>> So move to tick_nohz_stop_idle() to make the idle_exittime update
>> correctly.
>>
>> Signed-off-by: Yunfeng Ye <yeyunf...@huawei.com>
>> ---
>> kernel/time/tick-sched.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
>> index 749ec2a583de..be2e5d772d50 100644
>> --- a/kernel/time/tick-sched.c
>> +++ b/kernel/time/tick-sched.c
>> @@ -591,6 +591,7 @@ static void tick_nohz_stop_idle(struct tick_sched *ts,
>> ktime_t now)
>> {
>> update_ts_time_stats(smp_processor_id(), ts, now, NULL);
>> ts->idle_active = 0;
>> + ts->idle_exittime = now;
>
> This changes a bit the meaning of idle_exittime then since this is also called
> from idle interrupt entry.
>
> __tick_nohz_idle_restart_tick() would be a better place.
>
So is it necessary to modify the comment "@idle_exittime: Time when the
idle state was left" ?
On the other hand, if the patch "nohz: Update tick instead of restarting tick
in tick_nohz_idle_exit()"
(https://www.spinics.net/lists/kernel/msg3747039.html ) applied,
__tick_nohz_idle_restart_tick will not
be called always, So is it put here also a better place?
Thanks.
> Thanks.
>
>>
>> sched_clock_idle_wakeup_event();
>> }
>> @@ -901,7 +902,6 @@ static void tick_nohz_restart_sched_tick(struct
>> tick_sched *ts, ktime_t now)
>> * Cancel the scheduled timer and restore the tick
>> */
>> ts->tick_stopped = 0;
>> - ts->idle_exittime = now;
>>
>> tick_nohz_restart(ts, now);
>> }
>> --
>> 2.18.4
>>
> .
>
