Messages in this thread Patch in this message | | | From | Anna-Maria Behnsen <> | Subject | [PATCH v8 03/25] timer: Do not IPI for deferrable timers | Date | Wed, 4 Oct 2023 14:34:32 +0200 |
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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 and 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> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> --- v8: Update comment
v6: new patch --- kernel/time/timer.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 63a8ce7177dd..7d06351aff54 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -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 CPU from entering dynticks and are + * not taken into account on 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 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 -- 2.39.2
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