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Message-Id: <20231004123454.15691-18-anna-maria@linutronix.de>
Date: Wed, 4 Oct 2023 14:34:46 +0200
From: Anna-Maria Behnsen <anna-maria@...utronix.de>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
John Stultz <jstultz@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Eric Dumazet <edumazet@...gle.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
Arjan van de Ven <arjan@...radead.org>,
"Paul E . McKenney" <paulmck@...nel.org>,
Frederic Weisbecker <frederic@...nel.org>,
Rik van Riel <riel@...riel.com>,
Steven Rostedt <rostedt@...dmis.org>,
Sebastian Siewior <bigeasy@...utronix.de>,
Giovanni Gherdovich <ggherdovich@...e.cz>,
Lukasz Luba <lukasz.luba@....com>,
"Gautham R . Shenoy" <gautham.shenoy@....com>,
Srinivas Pandruvada <srinivas.pandruvada@...el.com>,
K Prateek Nayak <kprateek.nayak@....com>,
Anna-Maria Behnsen <anna-maria@...utronix.de>,
Richard Cochran <richardcochran@...il.com>
Subject: [PATCH v8 17/25] timer: Retrieve next expiry of pinned/non-pinned timers separately
For the conversion of the NOHZ timer placement to a pull at expiry time
model it's required to have separate expiry times for the pinned and the
non-pinned (movable) timers. Therefore struct timer_events is introduced.
No functional change
Originally-by: Richard Cochran (linutronix GmbH) <richardcochran@...il.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
---
kernel/time/timer.c | 48 ++++++++++++++++++++++++++++++++++-----------
1 file changed, 37 insertions(+), 11 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 1cd214c2f3f1..4230fc6fa1ed 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -221,6 +221,11 @@ struct timer_base {
static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
+struct timer_events {
+ u64 local;
+ u64 global;
+};
+
#ifdef CONFIG_NO_HZ_COMMON
static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
@@ -1971,9 +1976,10 @@ static unsigned long next_timer_interrupt(struct timer_base *base)
return base->next_expiry;
}
-static inline unsigned long __get_next_timer_interrupt(unsigned long basej,
+static inline unsigned long __get_next_timer_interrupt(unsigned long basej, u64 basem,
struct timer_base *base_local,
- struct timer_base *base_global)
+ struct timer_base *base_global,
+ struct timer_events *tevt)
{
unsigned long nextevt, nextevt_local, nextevt_global;
bool local_first;
@@ -1996,12 +2002,32 @@ static inline unsigned long __get_next_timer_interrupt(unsigned long basej,
nextevt = local_first ? nextevt_local : nextevt_global;
- if (base_local->timers_pending || base_global->timers_pending) {
+ /*
+ * If the @nextevt is at max. one tick away, use @nextevt and store
+ * it in the local expiry value. The next global event is irrelevant in
+ * this case and can be left as KTIME_MAX.
+ */
+ if (time_before_eq(nextevt, basej + 1)) {
/* If we missed a tick already, force 0 delta */
if (time_before(nextevt, basej))
nextevt = basej;
+ tevt->local = basem + (u64)(nextevt - basej) * TICK_NSEC;
+ return tevt->local;
}
+ /*
+ * Update tevt->* values:
+ *
+ * If the local queue expires first, then the global event can
+ * be ignored. If the global queue is empty, nothing to do
+ * either.
+ */
+ if (!local_first && base_global->timers_pending)
+ tevt->global = basem + (u64)(nextevt_global - basej) * TICK_NSEC;
+
+ if (base_local->timers_pending)
+ tevt->local = basem + (u64)(nextevt_local - basej) * TICK_NSEC;
+
return nextevt;
}
@@ -2015,16 +2041,15 @@ static inline unsigned long __get_next_timer_interrupt(unsigned long basej,
*/
u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
{
+ struct timer_events tevt = { .local = KTIME_MAX, .global = KTIME_MAX };
struct timer_base *base_local, *base_global;
- u64 expires = KTIME_MAX;
- unsigned long nextevt;
/*
* Pretend that there is no timer pending if the cpu is offline.
* Possible pending timers will be migrated later to an active cpu.
*/
if (cpu_is_offline(smp_processor_id()))
- return expires;
+ return KTIME_MAX;
base_local = this_cpu_ptr(&timer_bases[BASE_LOCAL]);
base_global = this_cpu_ptr(&timer_bases[BASE_GLOBAL]);
@@ -2032,14 +2057,14 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
raw_spin_lock(&base_local->lock);
raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING);
- nextevt = __get_next_timer_interrupt(basej, base_local, base_global);
+ __get_next_timer_interrupt(basej, basem, base_local, base_global, &tevt);
raw_spin_unlock(&base_global->lock);
raw_spin_unlock(&base_local->lock);
- expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
+ tevt.local = min_t(u64, tevt.local, tevt.global);
- return cmp_next_hrtimer_event(basem, expires);
+ return cmp_next_hrtimer_event(basem, tevt.local);
}
/**
@@ -2055,6 +2080,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
*/
u64 timer_set_idle(unsigned long basej, u64 basem, bool *idle)
{
+ struct timer_events tevt = { .local = KTIME_MAX, .global = KTIME_MAX };
struct timer_base *base_local, *base_global;
unsigned long nextevt;
@@ -2073,7 +2099,7 @@ u64 timer_set_idle(unsigned long basej, u64 basem, bool *idle)
raw_spin_lock(&base_local->lock);
raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING);
- nextevt = __get_next_timer_interrupt(basej, base_local, base_global);
+ nextevt = __get_next_timer_interrupt(basej, basem, base_local, base_global, &tevt);
/*
* We have a fresh next event. Check whether we can forward the
@@ -2097,7 +2123,7 @@ u64 timer_set_idle(unsigned long basej, u64 basem, bool *idle)
raw_spin_unlock(&base_global->lock);
raw_spin_unlock(&base_local->lock);
- return basem + (u64)(nextevt - basej) * TICK_NSEC;
+ return min_t(u64, tevt.local, tevt.global);
}
/**
--
2.39.2
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