From: Peng Liu <[email protected]>
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 <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
---
kernel/time/hrtimer.c | 2 +-
kernel/time/tick-sched.c | 38 +++++++++++++++++---------------------
kernel/time/tick-sched.h | 2 +-
3 files changed, 19 insertions(+), 23 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 760793998cdd..355b5a957f7f 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -746,7 +746,7 @@ 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 d2501673028d..e90dbb7ae70a 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1433,9 +1433,6 @@ 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;
@@ -1444,16 +1441,9 @@ 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)
@@ -1532,7 +1522,9 @@ static enum hrtimer_restart tick_nohz_highres_handler(struct hrtimer *timer)
return HRTIMER_RESTART;
}
+#endif /* 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)
@@ -1545,15 +1537,18 @@ 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;
+#ifdef CONFIG_HIGH_RES_TIMERS
+ if (mode == NOHZ_MODE_HIGHRES)
+ ts->sched_timer.function = tick_nohz_highres_handler;
+#endif
/* Get the next period (per-CPU) */
hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
@@ -1566,13 +1561,14 @@ 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 (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);
@@ -1589,7 +1585,7 @@ void tick_cancel_sched_timer(int cpu)
ts->idle_sleeptime = idle_sleeptime;
ts->iowait_sleeptime = iowait_sleeptime;
}
-#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
On Wed, Jan 24 2024 at 18:04, Frederic Weisbecker wrote:
>
> /**
> * 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;
> +#ifdef CONFIG_HIGH_RES_TIMERS
> + if (mode == NOHZ_MODE_HIGHRES)
> + ts->sched_timer.function = tick_nohz_highres_handler;
> +#endif
Adding
#define tick_nohz_highres_handler NULL
for CONFIG_HIGH_RES_TIMERS=n somewhere allows you to write that as:
if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
ts->sched_timer.function = tick_nohz_highres_handler;
> + hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
> + if (mode == NOHZ_MODE_HIGHRES)
Wants a (IS_ENABLED(HIGRES) && mode == ...) no?
Thanks,
tglx
On Thu, Jan 25, 2024 at 10:12:20AM +0100, Thomas Gleixner wrote:
> On Wed, Jan 24 2024 at 18:04, Frederic Weisbecker wrote:
> >
> > /**
> > * 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;
> > +#ifdef CONFIG_HIGH_RES_TIMERS
> > + if (mode == NOHZ_MODE_HIGHRES)
> > + ts->sched_timer.function = tick_nohz_highres_handler;
> > +#endif
>
> Adding
>
> #define tick_nohz_highres_handler NULL
>
> for CONFIG_HIGH_RES_TIMERS=n somewhere allows you to write that as:
>
> if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
> ts->sched_timer.function = tick_nohz_highres_handler;
So the next patch does:
if (mode == NOHZ_MODE_HIGHRES)
ts->sched_timer.function = tick_nohz_highres_handler;
Because that condition only happens in CONFIG_HIGH_RES_TIMERS anyway
and the function field exists in any case.
I can move that to the current patch though.
>
> > + hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
> > + if (mode == NOHZ_MODE_HIGHRES)
>
> Wants a (IS_ENABLED(HIGRES) && mode == ...) no?
Hmm, indeed hrtimer_start_range_ns() called by hrtimer_start_expires()
is only defined if CONFIG_HIGH_RES_TIMERS=y. I'll resend.
Thanks.
>
> Thanks,
>
> tglx
On Thu, Jan 25 2024 at 12:57, Frederic Weisbecker wrote:
> On Thu, Jan 25, 2024 at 10:12:20AM +0100, Thomas Gleixner wrote:
>> Adding
>>
>> #define tick_nohz_highres_handler NULL
>>
>> for CONFIG_HIGH_RES_TIMERS=n somewhere allows you to write that as:
>>
>> if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
>> ts->sched_timer.function = tick_nohz_highres_handler;
>
> So the next patch does:
>
> if (mode == NOHZ_MODE_HIGHRES)
> ts->sched_timer.function = tick_nohz_highres_handler;
>
> Because that condition only happens in CONFIG_HIGH_RES_TIMERS anyway
> and the function field exists in any case.
Right, but the function does not exist for HRES=n, so you need the
#define ... NULL. The IS_ENABLED() allows the compiler to eliminate the
code for HRES=n completely.
Thanks,
tglx
On Thu, Jan 25, 2024 at 02:34:06PM +0100, Thomas Gleixner wrote:
> On Thu, Jan 25 2024 at 12:57, Frederic Weisbecker wrote:
> > On Thu, Jan 25, 2024 at 10:12:20AM +0100, Thomas Gleixner wrote:
> >> Adding
> >>
> >> #define tick_nohz_highres_handler NULL
> >>
> >> for CONFIG_HIGH_RES_TIMERS=n somewhere allows you to write that as:
> >>
> >> if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && mode == NOHZ_MODE_HIGHRES)
> >> ts->sched_timer.function = tick_nohz_highres_handler;
> >
> > So the next patch does:
> >
> > if (mode == NOHZ_MODE_HIGHRES)
> > ts->sched_timer.function = tick_nohz_highres_handler;
> >
> > Because that condition only happens in CONFIG_HIGH_RES_TIMERS anyway
> > and the function field exists in any case.
>
> Right, but the function does not exist for HRES=n, so you need the
> #define ... NULL. The IS_ENABLED() allows the compiler to eliminate the
> code for HRES=n completely.
Ah but the next patch moves tick_nohz_highres_handler out of CONFIG_HRES
(to soon become tick_nohz_handler()). But anyway I can add the IS_ENABLED()
to remove dead code.
Thanks.
>
> Thanks,
>
> tglx