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timers: Do not IPI for deferrable timers
Deferrable timers do not prevent CPU from going idle and are not taken into account on idle path. Sending an IPI to a remote CPU when a new first deferrable timer was enqueued will wake up the remote CPU but nothing will be done regarding the deferrable timers. Drop IPI completely when a new first deferrable timer was enqueued. Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20231201092654.34614-7-anna-maria@linutronix.de
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1 changed files with 6 additions and 9 deletions
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@ -571,18 +571,15 @@ static int calc_wheel_index(unsigned long expires, unsigned long clk,
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static void
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trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
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{
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if (!is_timers_nohz_active())
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return;
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/*
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* TODO: This wants some optimizing similar to the code below, but we
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* will do that when we switch from push to pull for deferrable timers.
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* Deferrable timers do not prevent the CPU from entering dynticks and
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* are not taken into account on the idle/nohz_full path. An IPI when a
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* new deferrable timer is enqueued will wake up the remote CPU but
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* nothing will be done with the deferrable timer base. Therefore skip
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* the remote IPI for deferrable timers completely.
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*/
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if (timer->flags & TIMER_DEFERRABLE) {
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if (tick_nohz_full_cpu(base->cpu))
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wake_up_nohz_cpu(base->cpu);
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if (!is_timers_nohz_active() || timer->flags & TIMER_DEFERRABLE)
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return;
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}
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/*
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* We might have to IPI the remote CPU if the base is idle and the
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