Commit d124c339 authored by Anna-Maria Behnsen's avatar Anna-Maria Behnsen Committed by Thomas Gleixner
Browse files

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: default avatarAnna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20231201092654.34614-7-anna-maria@linutronix.de
parent b573c731

kernel/time/timer.c

+6 −9
Original line number Diff line number Diff line
@@ -571,18 +571,15 @@ static int calc_wheel_index(unsigned long expires, unsigned long clk, 
static void

trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)

{

	if (!is_timers_nohz_active())

		return;



	/*

	 * TODO: This wants some optimizing similar to the code below, but we

	 * will do that when we switch from push to pull for deferrable timers.

	 * Deferrable timers do not prevent the CPU from entering dynticks and

	 * are not taken into account on the idle/nohz_full path. An IPI when a

	 * new deferrable timer is enqueued will wake up the remote CPU but

	 * nothing will be done with the deferrable timer base. Therefore skip

	 * the remote IPI for deferrable timers completely.

	 */

	if (timer->flags & TIMER_DEFERRABLE) {

		if (tick_nohz_full_cpu(base->cpu))

			wake_up_nohz_cpu(base->cpu);

	if (!is_timers_nohz_active() || timer->flags & TIMER_DEFERRABLE)

		return;

	}



	/*

	 * We might have to IPI the remote CPU if the base is idle and the