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![Venki Pallipadi](/assets/img/avatar_default.png)
Introduce a new flag for timers - deferrable: Timers that work normally when system is busy. But, will not cause CPU to come out of idle (just to service this timer), when CPU is idle. Instead, this timer will be serviced when CPU eventually wakes up with a subsequent non-deferrable timer. The main advantage of this is to avoid unnecessary timer interrupts when CPU is idle. If the routine currently called by a timer can wait until next event without any issues, this new timer can be used to setup timer event for that routine. This, with dynticks, allows CPUs to be lazy, allowing them to stay in idle for extended period of time by reducing unnecesary wakeup and thereby reducing the power consumption. This patch: Builds this new timer on top of existing timer infrastructure. It uses last bit in 'base' pointer of timer_list structure to store this deferrable timer flag. __next_timer_interrupt() function skips over these deferrable timers when CPU looks for next timer event for which it has to wake up. This is exported by a new interface init_timer_deferrable() that can be called in place of regular init_timer(). [akpm@linux-foundation.org: Privatise a #define] Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Dave Jones <davej@codemonkey.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
172 lines
4.4 KiB
C
172 lines
4.4 KiB
C
#ifndef _LINUX_TIMER_H
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#define _LINUX_TIMER_H
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#include <linux/list.h>
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#include <linux/ktime.h>
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#include <linux/spinlock.h>
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#include <linux/stddef.h>
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struct tvec_t_base_s;
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struct timer_list {
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struct list_head entry;
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unsigned long expires;
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void (*function)(unsigned long);
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unsigned long data;
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struct tvec_t_base_s *base;
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#ifdef CONFIG_TIMER_STATS
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void *start_site;
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char start_comm[16];
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int start_pid;
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#endif
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};
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extern struct tvec_t_base_s boot_tvec_bases;
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#define TIMER_INITIALIZER(_function, _expires, _data) { \
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.function = (_function), \
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.expires = (_expires), \
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.data = (_data), \
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.base = &boot_tvec_bases, \
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}
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#define DEFINE_TIMER(_name, _function, _expires, _data) \
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struct timer_list _name = \
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TIMER_INITIALIZER(_function, _expires, _data)
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void fastcall init_timer(struct timer_list * timer);
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void fastcall init_timer_deferrable(struct timer_list *timer);
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static inline void setup_timer(struct timer_list * timer,
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void (*function)(unsigned long),
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unsigned long data)
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{
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timer->function = function;
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timer->data = data;
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init_timer(timer);
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}
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/**
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* timer_pending - is a timer pending?
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* @timer: the timer in question
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*
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* timer_pending will tell whether a given timer is currently pending,
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* or not. Callers must ensure serialization wrt. other operations done
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* to this timer, eg. interrupt contexts, or other CPUs on SMP.
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*
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* return value: 1 if the timer is pending, 0 if not.
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*/
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static inline int timer_pending(const struct timer_list * timer)
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{
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return timer->entry.next != NULL;
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}
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extern void add_timer_on(struct timer_list *timer, int cpu);
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extern int del_timer(struct timer_list * timer);
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extern int __mod_timer(struct timer_list *timer, unsigned long expires);
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extern int mod_timer(struct timer_list *timer, unsigned long expires);
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/*
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* Return when the next timer-wheel timeout occurs (in absolute jiffies),
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* locks the timer base:
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*/
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extern unsigned long next_timer_interrupt(void);
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/*
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* Return when the next timer-wheel timeout occurs (in absolute jiffies),
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* locks the timer base and does the comparison against the given
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* jiffie.
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*/
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extern unsigned long get_next_timer_interrupt(unsigned long now);
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/*
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* Timer-statistics info:
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*/
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#ifdef CONFIG_TIMER_STATS
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extern void init_timer_stats(void);
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extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
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void *timerf, char * comm);
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static inline void timer_stats_account_timer(struct timer_list *timer)
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{
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timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
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timer->function, timer->start_comm);
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}
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extern void __timer_stats_timer_set_start_info(struct timer_list *timer,
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void *addr);
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static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
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{
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__timer_stats_timer_set_start_info(timer, __builtin_return_address(0));
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}
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static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
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{
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timer->start_site = NULL;
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}
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#else
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static inline void init_timer_stats(void)
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{
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}
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static inline void timer_stats_account_timer(struct timer_list *timer)
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{
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}
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static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
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{
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}
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static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
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{
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}
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#endif
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extern void delayed_work_timer_fn(unsigned long __data);
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/**
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* add_timer - start a timer
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* @timer: the timer to be added
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*
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* The kernel will do a ->function(->data) callback from the
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* timer interrupt at the ->expires point in the future. The
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* current time is 'jiffies'.
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*
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* The timer's ->expires, ->function (and if the handler uses it, ->data)
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* fields must be set prior calling this function.
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*
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* Timers with an ->expires field in the past will be executed in the next
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* timer tick.
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*/
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static inline void add_timer(struct timer_list *timer)
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{
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BUG_ON(timer_pending(timer));
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__mod_timer(timer, timer->expires);
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}
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#ifdef CONFIG_SMP
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extern int try_to_del_timer_sync(struct timer_list *timer);
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extern int del_timer_sync(struct timer_list *timer);
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#else
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# define try_to_del_timer_sync(t) del_timer(t)
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# define del_timer_sync(t) del_timer(t)
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#endif
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#define del_singleshot_timer_sync(t) del_timer_sync(t)
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extern void init_timers(void);
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extern void run_local_timers(void);
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struct hrtimer;
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extern enum hrtimer_restart it_real_fn(struct hrtimer *);
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unsigned long __round_jiffies(unsigned long j, int cpu);
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unsigned long __round_jiffies_relative(unsigned long j, int cpu);
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unsigned long round_jiffies(unsigned long j);
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unsigned long round_jiffies_relative(unsigned long j);
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#endif
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