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authorAnna-Maria Behnsen <anna-maria@linutronix.de>2023-12-01 10:26:28 +0100
committerThomas Gleixner <tglx@linutronix.de>2023-12-20 16:49:38 +0100
commitd124c3393e798b1fb142ee728d5c8976d11e722d (patch)
tree458ebf8804f3a74fd641a4dbe5ad8c39af5bab60 /kernel/time
parentb573c73101d8786446535b2ab28cbc8907bda9a9 (diff)
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
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/timer.c15
1 files changed, 6 insertions, 9 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index ed8d6063d9ef..91882059bf3d 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 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