From 1f8a4212dc83f8353843fabf6465fd918372fbbf Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 17 Jul 2020 16:05:48 +0200 Subject: 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 Signed-off-by: Thomas Gleixner Tested-by: Juri Lelli Link: https://lkml.kernel.org/r/20200717140551.29076-10-frederic@kernel.org --- kernel/time/timer.c | 26 ++++---------------------- 1 file changed, 4 insertions(+), 22 deletions(-) (limited to 'kernel/time') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 13f48ee708aa..1be92b53b75f 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); } -- cgit v1.2.3-70-g09d2