[PATCH 01/16] tick/nohz: Remove duplicate between tick_nohz_switch_to_nohz() and tick_setup_sched_timer()

Frederic Weisbecker
2024-02-25T22:55:16Z

From: Peng Liu <liupeng17@lenovo.com>

The ts->sched_timer initialization work of tick_nohz_switch_to_nohz()
is almost the same as that of tick_setup_sched_timer(), so adjust the
latter to get it reused by tick_nohz_switch_to_nohz().

This also makes low-res mode sched_timer benefit from the tick skew
boot option.

Signed-off-by: Peng Liu <liupeng17@lenovo.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
kernel/time/hrtimer.c | 2 +-
kernel/time/tick-sched.c | 39 ++++++++++++++++++---------------------
kernel/time/tick-sched.h | 2 +-
3 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 1fd106af747d..95f1f351dcd9 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -747,7 +747,7 @@ static void hrtimer_switch_to_hres(void)
base->hres_active = 1;
hrtimer_resolution = HIGH_RES_NSEC;

- tick_setup_sched_timer();
+ tick_setup_sched_timer(NOHZ_MODE_HIGHRES);
/* "Retrigger" the interrupt to get things going */
retrigger_next_event(NULL);
}
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 417bb7f880ca..d4901654148d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1471,9 +1471,6 @@ static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
*/
static void tick_nohz_switch_to_nohz(void)
{
- struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
- ktime_t next;
-
if (!tick_nohz_enabled)
return;

@@ -1482,16 +1479,9 @@ static void tick_nohz_switch_to_nohz(void)

/*
* Recycle the hrtimer in 'ts', so we can share the
- * hrtimer_forward_now() function with the highres code.
+ * highres code.
*/
- hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
- /* Get the next period */
- next = tick_init_jiffy_update();
-
- hrtimer_set_expires(&ts->sched_timer, next);
- hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
- tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
- tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
+ tick_setup_sched_timer(NOHZ_MODE_LOWRES);
}

static inline void tick_nohz_irq_enter(void)
@@ -1570,7 +1560,11 @@ static enum hrtimer_restart tick_nohz_highres_handler(struct hrtimer *timer)

return HRTIMER_RESTART;
}
+#else
+#define tick_nohz_highres_handler NULL
+#endif /* CONFIG_HIGH_RES_TIMERS */

+#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
static int sched_skew_tick;

static int __init skew_tick(char *str)
@@ -1583,15 +1577,17 @@ early_param("skew_tick", skew_tick);

/**
* tick_setup_sched_timer - setup the tick emulation timer
+ * @mode: tick_nohz_mode to setup for
*/
-void tick_setup_sched_timer(void)
+void tick_setup_sched_timer(int mode)
{
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
- ktime_t now = ktime_get();

/* Emulate tick processing via per-CPU hrtimers: */
hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
- ts->sched_timer.function = tick_nohz_highres_handler;
+
+ if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
+ ts->sched_timer.function = tick_nohz_highres_handler;

/* Get the next period (per-CPU) */
hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
@@ -1604,13 +1600,14 @@ void tick_setup_sched_timer(void)
hrtimer_add_expires_ns(&ts->sched_timer, offset);
}

- hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
- hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
- tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
+ hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
+ if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
+ hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
+ else
+ tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+ tick_nohz_activate(ts, mode);
}
-#endif /* HIGH_RES_TIMERS */

-#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
void tick_cancel_sched_timer(int cpu)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
@@ -1632,7 +1629,7 @@ void tick_cancel_sched_timer(int cpu)
ts->idle_calls = idle_calls;
ts->idle_sleeps = idle_sleeps;
}
-#endif
+#endif /* CONFIG_NO_HZ_COMMON || CONFIG_HIGH_RES_TIMERS */

/*
* Async notification about clocksource changes
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 5ed5a9d41d5a..35808bbb8a47 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -102,7 +102,7 @@ struct tick_sched {

extern struct tick_sched *tick_get_tick_sched(int cpu);

-extern void tick_setup_sched_timer(void);
+extern void tick_setup_sched_timer(int mode);
#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
extern void tick_cancel_sched_timer(int cpu);
#else
--
2.43.0