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Commit 92127c7a authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
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[PATCH] hrtimers: optimize softirq runqueues 



The hrtimer softirq is called from the timer softirq every tick.  Retrieve the
current time from xtime and wall_to_monotonic instead of calling
base->get_time() for each timer base.  Store the time in the base structure
and provide a hook once clock source abstractions are in place and to keep the
code open for new base clocks.

Based on a patch from: Roman Zippel <zippel@linux-m68k.org>

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a0e92852

include/linux/hrtimer.h

+12 −8
Original line number Diff line number Diff line
@@ -79,7 +79,9 @@ struct hrtimer { 
 * @first:		pointer to the timer node which expires first

 * @resolution:		the resolution of the clock, in nanoseconds

 * @get_time:		function to retrieve the current time of the clock

 * @get_sofirq_time:	function to retrieve the current time from the softirq

 * @curr_timer:		the timer which is executing a callback right now

 * @softirq_time:	the time when running the hrtimer queue in the softirq

 */

struct hrtimer_base {

	clockid_t		index;
@@ -88,7 +90,9 @@ struct hrtimer_base { 
	struct rb_node		*first;

	ktime_t			resolution;

	ktime_t			(*get_time)(void);

	ktime_t			(*get_softirq_time)(void);

	struct hrtimer		*curr_timer;

	ktime_t			softirq_time;

};



/*

kernel/hrtimer.c

+26 −2
Original line number Diff line number Diff line
@@ -122,6 +122,26 @@ void ktime_get_ts(struct timespec *ts) 
}

EXPORT_SYMBOL_GPL(ktime_get_ts);



/*

 * Get the coarse grained time at the softirq based on xtime and

 * wall_to_monotonic.

 */

static void hrtimer_get_softirq_time(struct hrtimer_base *base)

{

	ktime_t xtim, tomono;

	unsigned long seq;



	do {

		seq = read_seqbegin(&xtime_lock);

		xtim = timespec_to_ktime(xtime);

		tomono = timespec_to_ktime(wall_to_monotonic);



	} while (read_seqretry(&xtime_lock, seq));



	base[CLOCK_REALTIME].softirq_time = xtim;

	base[CLOCK_MONOTONIC].softirq_time = ktime_add(xtim, tomono);

}



/*

 * Functions and macros which are different for UP/SMP systems are kept in a

 * single place
@@ -586,9 +606,11 @@ int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp) 
 */

static inline void run_hrtimer_queue(struct hrtimer_base *base)

{

	ktime_t now = base->get_time();

	struct rb_node *node;



	if (base->get_softirq_time)

		base->softirq_time = base->get_softirq_time();



	spin_lock_irq(&base->lock);



	while ((node = base->first)) {
@@ -598,7 +620,7 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base) 
		void *data;



		timer = rb_entry(node, struct hrtimer, node);

		if (now.tv64 <= timer->expires.tv64)

		if (base->softirq_time.tv64 <= timer->expires.tv64)

			break;



		fn = timer->function;
@@ -641,6 +663,8 @@ void hrtimer_run_queues(void) 
	struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);

	int i;



	hrtimer_get_softirq_time(base);



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

		run_hrtimer_queue(&base[i]);

}