From: "tip-bot2 for Frederic Weisbecker" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Frederic Weisbecker <frederic@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>, x86 <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: [tip: timers/core] timers: Expand clk forward logic beyond nohz
Date: Fri, 17 Jul 2020 20:00:16 -0000 [thread overview]
Message-ID: <159501601684.4006.18089332729710334046.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20200717140551.29076-10-frederic@kernel.org>
The following commit has been merged into the timers/core branch of tip:
Commit-ID: 1f8a4212dc83f8353843fabf6465fd918372fbbf
Gitweb: https://git.kernel.org/tip/1f8a4212dc83f8353843fabf6465fd918372fbbf
Author: Frederic Weisbecker <frederic@kernel.org>
AuthorDate: Fri, 17 Jul 2020 16:05:48 +02:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Fri, 17 Jul 2020 21:55:24 +02:00
timers: Expand clk forward logic beyond nohz
As for next_expiry, the base->clk catch up logic will be expanded beyond
NOHZ in order to avoid triggering useless softirqs.
If softirqs should only fire to expire pending timers, periodic base->clk
increments must be skippable for random amounts of time. Therefore prepare
to catch-up with missing updates whenever an up-to-date base clock is
needed.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-10-frederic@kernel.org
---
kernel/time/timer.c | 26 ++++----------------------
1 file changed, 4 insertions(+), 22 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 13f48ee..1be92b5 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -888,19 +888,12 @@ get_target_base(struct timer_base *base, unsigned tflags)
static inline void forward_timer_base(struct timer_base *base)
{
-#ifdef CONFIG_NO_HZ_COMMON
unsigned long jnow;
- /*
- * We only forward the base when we are idle or have just come out of
- * idle (must_forward_clk logic), and have a delta between base clock
- * and jiffies. In the common case, run_timers will take care of it.
- */
- if (likely(!base->must_forward_clk))
+ if (!base->must_forward_clk)
return;
jnow = READ_ONCE(jiffies);
- base->must_forward_clk = base->is_idle;
if ((long)(jnow - base->clk) < 2)
return;
@@ -915,7 +908,6 @@ static inline void forward_timer_base(struct timer_base *base)
return;
base->clk = base->next_expiry;
}
-#endif
}
@@ -1667,10 +1659,8 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
* logic is only maintained for the BASE_STD base, deferrable
* timers may still see large granularity skew (by design).
*/
- if ((expires - basem) > TICK_NSEC) {
- base->must_forward_clk = true;
+ if ((expires - basem) > TICK_NSEC)
base->is_idle = true;
- }
}
raw_spin_unlock(&base->lock);
@@ -1769,16 +1759,7 @@ static inline void __run_timers(struct timer_base *base)
/*
* timer_base::must_forward_clk must be cleared before running
* timers so that any timer functions that call mod_timer() will
- * not try to forward the base. Idle tracking / clock forwarding
- * logic is only used with BASE_STD timers.
- *
- * The must_forward_clk flag is cleared unconditionally also for
- * the deferrable base. The deferrable base is not affected by idle
- * tracking and never forwarded, so clearing the flag is a NOOP.
- *
- * The fact that the deferrable base is never forwarded can cause
- * large variations in granularity for deferrable timers, but they
- * can be deferred for long periods due to idle anyway.
+ * not try to forward the base.
*/
base->must_forward_clk = false;
@@ -1791,6 +1772,7 @@ static inline void __run_timers(struct timer_base *base)
while (levels--)
expire_timers(base, heads + levels);
}
+ base->must_forward_clk = true;
raw_spin_unlock_irq(&base->lock);
timer_base_unlock_expiry(base);
}
next prev parent reply other threads:[~2020-07-17 20:00 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 14:05 [PATCH 00/11] timer: Reduce timers softirq v3 Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 01/12] timer: Fix wheel index calculation on last level Frederic Weisbecker
2020-07-17 19:49 ` [tip: timers/urgent] " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 02/12] timer: Preserve higher bits of expiration on index calculation Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 03/12] timers: Use only bucket expiry for base->next_expiry value Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] " tip-bot2 for Anna-Maria Behnsen
2020-07-17 14:05 ` [PATCH 04/12] timer: Move trigger_dyntick_cpu() to enqueue_timer() Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 05/12] timer: Add comments about calc_index() ceiling work Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 06/12] timer: Optimize _next_timer_interrupt() level iteration Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 07/12] timers: Always keep track of next expiry Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 08/12] timer: Reuse next expiry cache after nohz exit Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 09/12] timer: Expand clk forward logic beyond nohz Frederic Weisbecker
2020-07-17 20:00 ` tip-bot2 for Frederic Weisbecker [this message]
2020-07-17 14:05 ` [PATCH 10/12] timer: Spare timer softirq until next expiry Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 11/12] timer: Remove must_forward_clk Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 12/12] timer: Lower base clock forwarding threshold Frederic Weisbecker
2020-07-17 20:00 ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
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