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Commit 79bf2bb3 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
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[PATCH] tick-management: dyntick / highres functionality 



With Ingo Molnar <mingo@elte.hu>

Add functions to provide dynamic ticks and high resolution timers.  The code
which keeps track of jiffies and handles the long idle periods is shared
between tick based and high resolution timer based dynticks.  The dyntick
functionality can be disabled on the kernel commandline.  Provide also the
infrastructure to support high resolution timers.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f8381cba

Documentation/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -1078,6 +1078,10 @@ and is between 256 and 4096 characters. It is defined in the file 
			in certain environments such as networked servers or

			real-time systems.



	nohz=		[KNL] Boottime enable/disable dynamic ticks

			Valid arguments: on, off

			Default: on



	noirqbalance	[IA-32,SMP,KNL] Disable kernel irq balancing



	noirqdebug	[IA-32] Disables the code which attempts to detect and

include/linux/hardirq.h

+11 −1
Original line number Diff line number Diff line
@@ -106,6 +106,16 @@ static inline void account_system_vtime(struct task_struct *tsk) 
 * always balanced, so the interrupted value of ->hardirq_context

 * will always be restored.

 */

#define __irq_enter()					\

	do {						\

		account_system_vtime(current);		\

		add_preempt_count(HARDIRQ_OFFSET);	\

		trace_hardirq_enter();			\

	} while (0)



/*

 * Enter irq context (on NO_HZ, update jiffies):

 */

extern void irq_enter(void);



/*
@@ -123,7 +133,7 @@ extern void irq_enter(void); 
 */

extern void irq_exit(void);



#define nmi_enter()		do { lockdep_off(); irq_enter(); } while (0)

#define nmi_enter()		do { lockdep_off(); __irq_enter(); } while (0)

#define nmi_exit()		do { __irq_exit(); lockdep_on(); } while (0)



#endif /* LINUX_HARDIRQ_H */

include/linux/hrtimer.h

+6 −0
Original line number Diff line number Diff line
@@ -201,4 +201,10 @@ extern void hrtimer_run_queues(void); 
/* Bootup initialization: */

extern void __init hrtimers_init(void);



#if BITS_PER_LONG < 64

extern unsigned long ktime_divns(const ktime_t kt, s64 div);

#else /* BITS_PER_LONG < 64 */

# define ktime_divns(kt, div)		(unsigned long)((kt).tv64 / (div))

#endif



#endif

include/linux/tick.h

+69 −2
Original line number Diff line number Diff line
@@ -20,12 +20,79 @@ struct tick_device { 
	enum tick_device_mode mode;

};



enum tick_nohz_mode {

	NOHZ_MODE_INACTIVE,

	NOHZ_MODE_LOWRES,

	NOHZ_MODE_HIGHRES,

};



/**

 * struct tick_sched - sched tick emulation and no idle tick control/stats

 * @sched_timer:	hrtimer to schedule the periodic tick in high

 *			resolution mode

 * @idle_tick:		Store the last idle tick expiry time when the tick

 *			timer is modified for idle sleeps. This is necessary

 *			to resume the tick timer operation in the timeline

 *			when the CPU returns from idle

 * @tick_stopped:	Indicator that the idle tick has been stopped

 * @idle_jiffies:	jiffies at the entry to idle for idle time accounting

 * @idle_calls:		Total number of idle calls

 * @idle_sleeps:	Number of idle calls, where the sched tick was stopped

 * @idle_entrytime:	Time when the idle call was entered

 * @idle_sleeptime:	Sum of the time slept in idle with sched tick stopped

 */

struct tick_sched {

	struct hrtimer			sched_timer;

	unsigned long			check_clocks;

	enum tick_nohz_mode		nohz_mode;

	ktime_t				idle_tick;

	int				tick_stopped;

	unsigned long			idle_jiffies;

	unsigned long			idle_calls;

	unsigned long			idle_sleeps;

	ktime_t				idle_entrytime;

	ktime_t				idle_sleeptime;

	unsigned long			last_jiffies;

	unsigned long			next_jiffies;

	ktime_t				idle_expires;

};



extern void __init tick_init(void);

extern int tick_is_oneshot_available(void);



# ifdef CONFIG_HIGH_RES_TIMERS

extern int tick_init_highres(void);

extern int tick_program_event(ktime_t expires, int force);

extern void tick_setup_sched_timer(void);

extern void tick_cancel_sched_timer(int cpu);

# else

static inline void tick_cancel_sched_timer(int cpu) { }

# endif /* HIGHRES */



# ifdef CONFIG_TICK_ONESHOT

extern void tick_clock_notify(void);

extern int tick_check_oneshot_change(int allow_nohz);

extern struct tick_sched *tick_get_tick_sched(int cpu);

# else

static inline void tick_clock_notify(void) { }

static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }

# endif



#else /* CONFIG_GENERIC_CLOCKEVENTS */

static inline void tick_init(void) { }

static inline void tick_cancel_sched_timer(int cpu) { }

static inline void tick_clock_notify(void) { }

static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }

#endif /* !CONFIG_GENERIC_CLOCKEVENTS */



#endif

# ifdef CONFIG_NO_HZ

extern void tick_nohz_stop_sched_tick(void);

extern void tick_nohz_restart_sched_tick(void);

extern void tick_nohz_update_jiffies(void);

# else

static inline void tick_nohz_stop_sched_tick(void) { }

static inline void tick_nohz_restart_sched_tick(void) { }

static inline void tick_nohz_update_jiffies(void) { }

# endif /* !NO_HZ */



#endif

kernel/hrtimer.c

+14 −6
Original line number Diff line number Diff line
@@ -2,8 +2,8 @@ 
 *  linux/kernel/hrtimer.c

 *

 *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>

 *  Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar

 *  Copyright(C) 2006	    Timesys Corp., Thomas Gleixner <tglx@timesys.com>

 *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar

 *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner <tglx@timesys.com>

 *

 *  High-resolution kernel timers

 *
@@ -38,6 +38,7 @@ 
#include <linux/notifier.h>

#include <linux/syscalls.h>

#include <linux/interrupt.h>

#include <linux/tick.h>



#include <asm/uaccess.h>
@@ -288,7 +289,7 @@ ktime_t ktime_add_ns(const ktime_t kt, u64 nsec) 
/*

 * Divide a ktime value by a nanosecond value

 */

static unsigned long ktime_divns(const ktime_t kt, s64 div)

unsigned long ktime_divns(const ktime_t kt, s64 div)

{

	u64 dclc, inc, dns;

	int sft = 0;
@@ -305,9 +306,6 @@ static unsigned long ktime_divns(const ktime_t kt, s64 div) 


	return (unsigned long) dclc;

}



#else /* BITS_PER_LONG < 64 */

# define ktime_divns(kt, div)		(unsigned long)((kt).tv64 / (div))

#endif /* BITS_PER_LONG >= 64 */



/*
@@ -682,6 +680,16 @@ void hrtimer_run_queues(void) 
	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);

	int i;



	/*

	 * This _is_ ugly: We have to check in the softirq context,

	 * whether we can switch to highres and / or nohz mode. The

	 * clocksource switch happens in the timer interrupt with

	 * xtime_lock held. Notification from there only sets the

	 * check bit in the tick_oneshot code, otherwise we might

	 * deadlock vs. xtime_lock.

	 */

	tick_check_oneshot_change(1);



	hrtimer_get_softirq_time(cpu_base);



	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)