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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: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Anna-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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Anna-Maria Gleixner 2017-12-21 11:41:39 +01:00 committed by Ingo Molnar
parent 63e2ed3659
commit c272ca58c3
1 changed files with 21 additions and 10 deletions
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31
kernel/time/hrtimer.c
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@ -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))) {