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| author | Thomas Gleixner <tglx@linutronix.de> | 2015-05-26 22:50:35 +0000 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2015-06-19 15:18:28 +0200 |
| commit | 683be13a284720205228e29207ef11a1c3c322b9 (patch) | |
| tree | 02a925c3d34bd79de893c152d793aae46218a113 /kernel/time/tick-internal.h | |
| parent | bc7a34b8b9ebfb0f4b8a35a72a0b134fd6c5ef50 (diff) | |
| download | linux-683be13a284720205228e29207ef11a1c3c322b9.tar.gz linux-683be13a284720205228e29207ef11a1c3c322b9.tar.bz2 linux-683be13a284720205228e29207ef11a1c3c322b9.zip | |
timer: Minimize nohz off overhead
If nohz is disabled on the kernel command line the [hr]timer code
still calls wake_up_nohz_cpu() and tick_nohz_full_cpu(), a pretty
pointless exercise. Cache nohz_active in [hr]timer per cpu bases and
avoid the overhead.
Before:
48.10% hog [.] main
15.25% [kernel] [k] _raw_spin_lock_irqsave
9.76% [kernel] [k] _raw_spin_unlock_irqrestore
6.50% [kernel] [k] mod_timer
6.44% [kernel] [k] lock_timer_base.isra.38
3.87% [kernel] [k] detach_if_pending
3.80% [kernel] [k] del_timer
2.67% [kernel] [k] internal_add_timer
1.33% [kernel] [k] __internal_add_timer
0.73% [kernel] [k] timerfn
0.54% [kernel] [k] wake_up_nohz_cpu
After:
48.73% hog [.] main
15.36% [kernel] [k] _raw_spin_lock_irqsave
9.77% [kernel] [k] _raw_spin_unlock_irqrestore
6.61% [kernel] [k] lock_timer_base.isra.38
6.42% [kernel] [k] mod_timer
3.90% [kernel] [k] detach_if_pending
3.76% [kernel] [k] del_timer
2.41% [kernel] [k] internal_add_timer
1.39% [kernel] [k] __internal_add_timer
0.76% [kernel] [k] timerfn
We probably should have a cached value for nohz full in the per cpu
bases as well to avoid the cpumask check. The base cache line is hot
already, the cpumask not necessarily.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Joonwoo Park <joonwoop@codeaurora.org>
Cc: Wenbo Wang <wenbo.wang@memblaze.com>
Link: http://lkml.kernel.org/r/20150526224512.207378134@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/tick-internal.h')
| -rw-r--r-- | kernel/time/tick-internal.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 2edde84744df..966a5a6fdd0a 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -156,9 +156,9 @@ extern unsigned long tick_nohz_active; #endif #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) -extern void timers_update_migration(void); +extern void timers_update_migration(bool update_nohz); #else -static inline void timers_update_migration(void) { } +static inline void timers_update_migration(bool update_nohz) { } #endif DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases); |