> When nohz_full CPU stops tick in tick_nohz_irq_exit(),
> It wouldn't be chosen to perform idle load balancing because it doesn't
> call nohz_balance_enter_idle() in tick_nohz_idle_stop_tick() when it
> becomes idle.
>
> tick_nohz_idle_stop_tick() is only called in idle state and
> nohz_balance_enter_idle() tracks the CPU which is part of nohz.idle_cpus_mask
> with rq->nohz_tick_stopped.
>
> Change tick_nohz_idle_stop_tick() to call nohz_balance_enter_idle()
> without checking !was_stopped so that nohz_full cpu can be chosen to
> perform idle load balancing when it enters idle state.
Would you eventually like to add the tag “Fixes” once more?
…
> +++ b/kernel/time/tick-sched.c
> @@ -1228,8 +1228,10 @@ void tick_nohz_idle_stop_tick(void)
> ts->idle_sleeps++;
> ts->idle_expires = expires;
>
> - if (!was_stopped && tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
> - ts->idle_jiffies = ts->last_jiffies;
> + if (tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
> + if (!was_stopped)
> + ts->idle_jiffies = ts->last_jiffies;
> +
> nohz_balance_enter_idle(cpu);
> }
…
I interpret these diff data in the way that you propose to reorder
two condition checks.
But I wonder still how “good” the presented change description fits to
the suggested source code adjustment.
Regards,
Markus
