From: Marcelo Tosatti <mtosatti@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>,
linux-kernel@vger.kernel.org,
Frederic Weisbecker <frederic@kernel.org>,
Peter Xu <peterx@redhat.com>,
Nitesh Narayan Lal <nitesh@redhat.com>,
Alex Belits <abelits@marvell.com>
Subject: [PATCH v3] hrtimer: avoid retrigger_next_event IPI
Date: Thu, 15 Apr 2021 12:39:35 -0300 [thread overview]
Message-ID: <20210415153935.GA69750@fuller.cnet> (raw)
In-Reply-To: <20210413170431.GA16190@fuller.cnet>
Setting the realtime clock triggers an IPI to all CPUs to reprogram
the clock event device.
However, only realtime and TAI clocks have their offsets updated
(and therefore potentially require a reprogram).
Instead of sending an IPI unconditionally, check each per CPU hrtimer base
whether it has active timers in the CLOCK_REALTIME and CLOCK_TAI bases. If
that's not the case, update the realtime and TAI base offsets remotely and
skip the IPI. This ensures that any subsequently armed timers on
CLOCK_REALTIME and CLOCK_TAI are evaluated with the correct offsets.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
v3:
- Nicer changelog (Thomas).
- Code style fixes (Thomas).
- Compilation warning with CONFIG_HIGH_RES_TIMERS=n (Thomas).
- Shrink preemption disabled section (Thomas).
v2:
- Only REALTIME and TAI bases are affected by offset-to-monotonic changes (Thomas).
- Don't special case nohz_full CPUs (Thomas).
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 5c9d968187ae..dd9c0d2f469f 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -871,6 +871,24 @@ static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram)
tick_program_event(expires, 1);
}
+#define CLOCK_SET_BASES ((1U << HRTIMER_BASE_REALTIME) | \
+ (1U << HRTIMER_BASE_REALTIME_SOFT) | \
+ (1U << HRTIMER_BASE_TAI) | \
+ (1U << HRTIMER_BASE_TAI_SOFT))
+
+static bool need_reprogram_timer(struct hrtimer_cpu_base *cpu_base)
+{
+ unsigned int active = 0;
+
+ if (cpu_base->softirq_activated)
+ return true;
+
+ active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT;
+ active = active | (cpu_base->active_bases & HRTIMER_ACTIVE_HARD);
+
+ return (cpu_base->active_bases & CLOCK_SET_BASES) != 0;
+}
+
/*
* Clock realtime was set
*
@@ -885,8 +903,32 @@ static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram)
void clock_was_set(void)
{
#ifdef CONFIG_HIGH_RES_TIMERS
- /* Retrigger the CPU local events everywhere */
- on_each_cpu(retrigger_next_event, NULL, 1);
+ cpumask_var_t mask;
+ int cpu;
+
+ if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
+ on_each_cpu(retrigger_next_event, NULL, 1);
+ goto set_timerfd;
+ }
+
+ /* Avoid interrupting CPUs if possible */
+ cpus_read_lock();
+ for_each_online_cpu(cpu) {
+ unsigned long flags;
+ struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
+
+ raw_spin_lock_irqsave(&cpu_base->lock, flags);
+ if (need_reprogram_timer(cpu_base))
+ cpumask_set_cpu(cpu, mask);
+ raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+ }
+
+ preempt_disable();
+ smp_call_function_many(mask, retrigger_next_event, NULL, 1);
+ preempt_enable();
+ cpus_read_unlock();
+ free_cpumask_var(mask);
+set_timerfd:
#endif
timerfd_clock_was_set();
}
next prev parent reply other threads:[~2021-04-15 15:40 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 13:53 [PATCH] hrtimer: avoid retrigger_next_event IPI Marcelo Tosatti
2021-04-07 19:28 ` kernel test robot
2021-04-07 22:14 ` Frederic Weisbecker
2021-04-08 12:27 ` Marcelo Tosatti
2021-04-09 14:15 ` Thomas Gleixner
2021-04-09 16:51 ` Marcelo Tosatti
2021-04-10 7:53 ` Thomas Gleixner
2021-04-13 17:04 ` [PATCH v2] " Marcelo Tosatti
2021-04-14 17:19 ` Thomas Gleixner
2021-04-15 15:39 ` Marcelo Tosatti [this message]
2021-04-15 18:59 ` [PATCH v3] " Thomas Gleixner
2021-04-15 20:40 ` [PATCH v4] " Marcelo Tosatti
2021-04-16 16:00 ` [PATCH v5] " Marcelo Tosatti
2021-04-16 17:13 ` Peter Xu
2021-04-17 16:24 ` Thomas Gleixner
2021-04-17 16:51 ` Thomas Gleixner
2021-04-19 18:56 ` Marcelo Tosatti
2021-04-19 19:39 ` [PATCH v6] " Marcelo Tosatti
2021-04-19 20:52 ` Thomas Gleixner
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