From: Anna-Maria Gleixner Date: Wed, 20 Dec 2017 17:12:59 +0100 Subject: [PATCH 10/29] hrtimer: Switch for loop to _ffs() evaluation Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.14/older/patches-4.14.15-rt13.tar.xz 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 an own function and is called via a macro as suggested by Peter Zijlstra. Suggested-by: Peter Zijlstra Signed-off-by: Anna-Maria Gleixner Signed-off-by: Sebastian Andrzej Siewior --- kernel/time/hrtimer.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -448,6 +448,23 @@ static inline void debug_deactivate(stru 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_t 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); @@ -1243,16 +1257,13 @@ static void __run_hrtimer(struct hrtimer 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))) {