Commit c272ca58 authored by Anna-Maria Gleixner's avatar Anna-Maria Gleixner Committed by Ingo Molnar
Browse files

hrtimer: Switch 'for' loop to _ffs() evaluation 



Looping over all clock bases to find active bits is suboptimal if not all
bases are active.

Avoid this by converting it to a __ffs() evaluation. The functionallity is
outsourced into its own function and is called via a macro as suggested by
Peter Zijlstra.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarAnna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: keescook@chromium.org
Link: http://lkml.kernel.org/r/20171221104205.7269-11-anna-maria@linutronix.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 63e2ed36

kernel/time/hrtimer.c

+21 −10
Original line number Diff line number Diff line
@@ -448,6 +448,23 @@ static inline void debug_deactivate(struct hrtimer *timer) 
	trace_hrtimer_cancel(timer);

}



static struct hrtimer_clock_base *

__next_base(struct hrtimer_cpu_base *cpu_base, unsigned int *active)

{

	unsigned int idx;



	if (!*active)

		return NULL;



	idx = __ffs(*active);

	*active &= ~(1U << idx);



	return &cpu_base->clock_base[idx];

}



#define for_each_active_base(base, cpu_base, active)	\

	while ((base = __next_base((cpu_base), &(active))))



#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)

static inline void hrtimer_update_next_timer(struct hrtimer_cpu_base *cpu_base,

					     struct hrtimer *timer)
@@ -459,18 +476,15 @@ static inline void hrtimer_update_next_timer(struct hrtimer_cpu_base *cpu_base, 


static ktime_t __hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base)

{

	struct hrtimer_clock_base *base = cpu_base->clock_base;

	struct hrtimer_clock_base *base;

	unsigned int active = cpu_base->active_bases;

	ktime_t expires, expires_next = KTIME_MAX;



	hrtimer_update_next_timer(cpu_base, NULL);

	for (; active; base++, active >>= 1) {

	for_each_active_base(base, cpu_base, active) {

		struct timerqueue_node *next;

		struct hrtimer *timer;



		if (!(active & 0x01))

			continue;



		next = timerqueue_getnext(&base->active);

		timer = container_of(next, struct hrtimer, node);

		expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
@@ -1241,16 +1255,13 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base, 


static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now)

{

	struct hrtimer_clock_base *base = cpu_base->clock_base;

	struct hrtimer_clock_base *base;

	unsigned int active = cpu_base->active_bases;



	for (; active; base++, active >>= 1) {

	for_each_active_base(base, cpu_base, active) {

		struct timerqueue_node *node;

		ktime_t basenow;



		if (!(active & 0x01))

			continue;



		basenow = ktime_add(now, base->offset);



		while ((node = timerqueue_getnext(&base->active))) {

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