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linux/kernel/time/tick-internal.h
Thomas Gleixner 683be13a28 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>
2015-06-19 15:18:28 +02:00

167 lines
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/*
* tick internal variable and functions used by low/high res code
*/
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include "timekeeping.h"
#include "tick-sched.h"
#ifdef CONFIG_GENERIC_CLOCKEVENTS
# define TICK_DO_TIMER_NONE -1
# define TICK_DO_TIMER_BOOT -2
DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
extern ktime_t tick_next_period;
extern ktime_t tick_period;
extern int tick_do_timer_cpu __read_mostly;
extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
extern void tick_handle_periodic(struct clock_event_device *dev);
extern void tick_check_new_device(struct clock_event_device *dev);
extern void tick_shutdown(unsigned int cpu);
extern void tick_suspend(void);
extern void tick_resume(void);
extern bool tick_check_replacement(struct clock_event_device *curdev,
struct clock_event_device *newdev);
extern void tick_install_replacement(struct clock_event_device *dev);
extern int tick_is_oneshot_available(void);
extern struct tick_device *tick_get_device(int cpu);
extern int clockevents_tick_resume(struct clock_event_device *dev);
/* Check, if the device is functional or a dummy for broadcast */
static inline int tick_device_is_functional(struct clock_event_device *dev)
{
return !(dev->features & CLOCK_EVT_FEAT_DUMMY);
}
static inline enum clock_event_state clockevent_get_state(struct clock_event_device *dev)
{
return dev->state_use_accessors;
}
static inline void clockevent_set_state(struct clock_event_device *dev,
enum clock_event_state state)
{
dev->state_use_accessors = state;
}
extern void clockevents_shutdown(struct clock_event_device *dev);
extern void clockevents_exchange_device(struct clock_event_device *old,
struct clock_event_device *new);
extern void clockevents_switch_state(struct clock_event_device *dev,
enum clock_event_state state);
extern int clockevents_program_event(struct clock_event_device *dev,
ktime_t expires, bool force);
extern void clockevents_handle_noop(struct clock_event_device *dev);
extern int __clockevents_update_freq(struct clock_event_device *dev, u32 freq);
extern ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt);
/* Broadcasting support */
# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
extern int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu);
extern void tick_install_broadcast_device(struct clock_event_device *dev);
extern int tick_is_broadcast_device(struct clock_event_device *dev);
extern void tick_shutdown_broadcast(unsigned int cpu);
extern void tick_suspend_broadcast(void);
extern void tick_resume_broadcast(void);
extern bool tick_resume_check_broadcast(void);
extern void tick_broadcast_init(void);
extern void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast);
extern int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq);
extern struct tick_device *tick_get_broadcast_device(void);
extern struct cpumask *tick_get_broadcast_mask(void);
# else /* !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST: */
static inline void tick_install_broadcast_device(struct clock_event_device *dev) { }
static inline int tick_is_broadcast_device(struct clock_event_device *dev) { return 0; }
static inline int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) { return 0; }
static inline void tick_do_periodic_broadcast(struct clock_event_device *d) { }
static inline void tick_shutdown_broadcast(unsigned int cpu) { }
static inline void tick_suspend_broadcast(void) { }
static inline void tick_resume_broadcast(void) { }
static inline bool tick_resume_check_broadcast(void) { return false; }
static inline void tick_broadcast_init(void) { }
static inline int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq) { return -ENODEV; }
/* Set the periodic handler in non broadcast mode */
static inline void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
{
dev->event_handler = tick_handle_periodic;
}
# endif /* !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST */
#else /* !GENERIC_CLOCKEVENTS: */
static inline void tick_suspend(void) { }
static inline void tick_resume(void) { }
#endif /* !GENERIC_CLOCKEVENTS */
/* Oneshot related functions */
#ifdef CONFIG_TICK_ONESHOT
extern void tick_setup_oneshot(struct clock_event_device *newdev,
void (*handler)(struct clock_event_device *),
ktime_t nextevt);
extern int tick_program_event(ktime_t expires, int force);
extern void tick_oneshot_notify(void);
extern int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *));
extern void tick_resume_oneshot(void);
static inline bool tick_oneshot_possible(void) { return true; }
extern int tick_oneshot_mode_active(void);
extern void tick_clock_notify(void);
extern int tick_check_oneshot_change(int allow_nohz);
extern int tick_init_highres(void);
#else /* !CONFIG_TICK_ONESHOT: */
static inline
void tick_setup_oneshot(struct clock_event_device *newdev,
void (*handler)(struct clock_event_device *),
ktime_t nextevt) { BUG(); }
static inline void tick_resume_oneshot(void) { BUG(); }
static inline int tick_program_event(ktime_t expires, int force) { return 0; }
static inline void tick_oneshot_notify(void) { }
static inline bool tick_oneshot_possible(void) { return false; }
static inline int tick_oneshot_mode_active(void) { return 0; }
static inline void tick_clock_notify(void) { }
static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
#endif /* !CONFIG_TICK_ONESHOT */
/* Functions related to oneshot broadcasting */
#if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_TICK_ONESHOT)
extern void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
extern void tick_broadcast_switch_to_oneshot(void);
extern void tick_shutdown_broadcast_oneshot(unsigned int cpu);
extern int tick_broadcast_oneshot_active(void);
extern void tick_check_oneshot_broadcast_this_cpu(void);
bool tick_broadcast_oneshot_available(void);
extern struct cpumask *tick_get_broadcast_oneshot_mask(void);
#else /* !(BROADCAST && ONESHOT): */
static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
static inline void tick_broadcast_switch_to_oneshot(void) { }
static inline void tick_shutdown_broadcast_oneshot(unsigned int cpu) { }
static inline int tick_broadcast_oneshot_active(void) { return 0; }
static inline void tick_check_oneshot_broadcast_this_cpu(void) { }
static inline bool tick_broadcast_oneshot_available(void) { return tick_oneshot_possible(); }
#endif /* !(BROADCAST && ONESHOT) */
/* NO_HZ_FULL internal */
#ifdef CONFIG_NO_HZ_FULL
extern void tick_nohz_init(void);
# else
static inline void tick_nohz_init(void) { }
#endif
#ifdef CONFIG_NO_HZ_COMMON
extern unsigned long tick_nohz_active;
#else
#define tick_nohz_active (0)
#endif
#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
extern void timers_update_migration(bool update_nohz);
#else
static inline void timers_update_migration(bool update_nohz) { }
#endif
DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases);
extern u64 get_next_timer_interrupt(unsigned long basej, u64 basem);
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