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Date: Thu, 8 Aug 2013 15:32:12 +0800
From: "ethan.zhao" <ethan.kernel@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>, johlstei@...eaurora.org,
yinghai@...nel.org, joe.jin@...cle.com
Subject: Re: [PATCH V3]hrtimer: Fix a performance regression by disable reprogramming in remove_hrtimer
Kernel 3.11-rc3 With peter's patch and disable C-state in BIOS, got 1 second better performance !
[root@...alhost ~]# time ./pip1m
real 0m4.399s
user 0m0.092s
sys 0m2.775s
[root@...alhost ~]# time ./pip1m
real 0m4.352s
user 0m0.099s
sys 0m2.751s
[root@...alhost ~]# time ./pip1m
real 0m4.328s
user 0m0.102s
sys 0m2.731s
Compared with default kernel 3.11-rc3 and disable C-states in BIOS, test case 4
4. Disable C1E C3 C6 C-states and SpeedStep in BIOS, default configuration of kernel 3.11-rc3.
[root@...alhost ~]# time ./pip1m
real 0m5.371s
user 0m0.102s
sys 0m3.253s
[root@...alhost ~]# time ./pip1m
real 0m5.329s
user 0m0.075s
sys 0m3.254s
That is great improvement, So it is worth to merge.
Thanks
Ethan
在 2013-7-29，下午7:57，Peter Zijlstra <peterz@...radead.org> 写道：
>
> So aside from the complete mess posted; how about something like this?
>
> *completely untested etc..*
>
> ---
> include/linux/hrtimer.h | 5 +++++
> kernel/hrtimer.c | 60 +++++++++++++++++++++++--------------------------
> 2 files changed, 33 insertions(+), 32 deletions(-)
>
> diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
> index d19a5c2..f2bcb9c 100644
> --- a/include/linux/hrtimer.h
> +++ b/include/linux/hrtimer.h
> @@ -185,6 +185,7 @@ struct hrtimer_cpu_base {
> ktime_t expires_next;
> int hres_active;
> int hang_detected;
> + int timers_removed;
> unsigned long nr_events;
> unsigned long nr_retries;
> unsigned long nr_hangs;
> @@ -261,6 +262,8 @@ static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
> #ifdef CONFIG_HIGH_RES_TIMERS
> struct clock_event_device;
>
> +extern void hrtimer_enter_idle(void);
> +
> extern void hrtimer_interrupt(struct clock_event_device *dev);
>
> /*
> @@ -296,6 +299,8 @@ extern void clock_was_set_delayed(void);
> # define MONOTONIC_RES_NSEC LOW_RES_NSEC
> # define KTIME_MONOTONIC_RES KTIME_LOW_RES
>
> +static inline void hrtimer_enter_idle(void) { }
> +
> static inline void hrtimer_peek_ahead_timers(void) { }
>
> /*
> diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
> index f0f4fe2..ffb16d3 100644
> --- a/kernel/hrtimer.c
> +++ b/kernel/hrtimer.c
> @@ -673,6 +673,27 @@ static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
> return ktime_get_update_offsets(offs_real, offs_boot, offs_tai);
> }
>
> +static void __hrtimer_reprogram_all(struct hrtimer_cpu_base *base)
> +{
> + if (!hrtimer_hres_active())
> + return;
> +
> + raw_spin_lock(&base->lock);
> + hrtimer_update_base(base);
> + hrtimer_force_reprogram(base, 0);
> + raw_spin_unlock(&base->lock);
> +}
> +
> +void hrtimer_enter_idle(void)
> +{
> + struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
> +
> + if (base->timers_removed) {
> + base->timers_removed = 0;
> + __hrtimer_reprogramm_all(base);
> + }
> +}
> +
> /*
> * Retrigger next event is called after clock was set
> *
> @@ -682,13 +703,7 @@ static void retrigger_next_event(void *arg)
> {
> struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
>
> - if (!hrtimer_hres_active())
> - return;
> -
> - raw_spin_lock(&base->lock);
> - hrtimer_update_base(base);
> - hrtimer_force_reprogram(base, 0);
> - raw_spin_unlock(&base->lock);
> + __hrtimer_reprogram_all(base);
> }
>
> /*
> @@ -907,7 +922,7 @@ static int enqueue_hrtimer(struct hrtimer *timer,
> */
> static void __remove_hrtimer(struct hrtimer *timer,
> struct hrtimer_clock_base *base,
> - unsigned long newstate, int reprogram)
> + unsigned long newstate)
> {
> struct timerqueue_node *next_timer;
> if (!(timer->state & HRTIMER_STATE_ENQUEUED))
> @@ -915,19 +930,10 @@ static void __remove_hrtimer(struct hrtimer *timer,
>
> next_timer = timerqueue_getnext(&base->active);
> timerqueue_del(&base->active, &timer->node);
> - if (&timer->node == next_timer) {
> #ifdef CONFIG_HIGH_RES_TIMERS
> - /* Reprogram the clock event device. if enabled */
> - if (reprogram && hrtimer_hres_active()) {
> - ktime_t expires;
> -
> - expires = ktime_sub(hrtimer_get_expires(timer),
> - base->offset);
> - if (base->cpu_base->expires_next.tv64 == expires.tv64)
> - hrtimer_force_reprogram(base->cpu_base, 1);
> - }
> + if (hrtimer_hres_active() && &timer->node == next_timer)
> + base->cpu_base->timers_removed++;
> #endif
> - }
> if (!timerqueue_getnext(&base->active))
> base->cpu_base->active_bases &= ~(1 << base->index);
> out:
> @@ -942,26 +948,16 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
> {
> if (hrtimer_is_queued(timer)) {
> unsigned long state;
> - int reprogram;
>
> - /*
> - * Remove the timer and force reprogramming when high
> - * resolution mode is active and the timer is on the current
> - * CPU. If we remove a timer on another CPU, reprogramming is
> - * skipped. The interrupt event on this CPU is fired and
> - * reprogramming happens in the interrupt handler. This is a
> - * rare case and less expensive than a smp call.
> - */
> debug_deactivate(timer);
> timer_stats_hrtimer_clear_start_info(timer);
> - reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
> /*
> * We must preserve the CALLBACK state flag here,
> * otherwise we could move the timer base in
> * switch_hrtimer_base.
> */
> state = timer->state & HRTIMER_STATE_CALLBACK;
> - __remove_hrtimer(timer, base, state, reprogram);
> + __remove_hrtimer(timer, base, state);
> return 1;
> }
> return 0;
> @@ -1243,7 +1239,7 @@ static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
> WARN_ON(!irqs_disabled());
>
> debug_deactivate(timer);
> - __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
> + __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK);
> timer_stats_account_hrtimer(timer);
> fn = timer->function;
>
> @@ -1690,7 +1686,7 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
> * timer could be seen as !active and just vanish away
> * under us on another CPU
> */
> - __remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE, 0);
> + __remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE);
> timer->base = new_base;
> /*
> * Enqueue the timers on the new cpu. This does not
--
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