linux-kernel - Re: [PATCH 11/13] hrtimer: turn hrtimers into range timers

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Date:	Tue, 02 Sep 2008 10:22:12 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	dwmw2@...radead.org, drepper@...hat.com, mingo@...e.hu,
	tglx@...x.de
Subject: Re: [PATCH 11/13] hrtimer: turn hrtimers into range timers

On Mon, 2008-09-01 at 16:08 -0700, Arjan van de Ven wrote:

> @@ -847,7 +847,8 @@ static void enqueue_hrtimer(struct hrtimer *timer,
>                  * We dont care about collisions. Nodes with
>                  * the same expiry time stay together.
>                  */
> -               if (timer->expires.tv64 < entry->expires.tv64) {
> +               if (hrtimer_get_expires_tv64(timer) <
> +                               hrtimer_get_expires_tv64(entry)) {
>                         link = &(*link)->rb_left;
>                 } else {
>                         link = &(*link)->rb_right;

On Mon, 2008-09-01 at 16:13 -0700, Arjan van de Ven wrote:

> +static inline void hrtimer_set_expires_range(struct hrtimer *timer, ktime_t time, ktime_t delta)
> +{
> +       timer->_softexpires = time;
> +       timer->_expires = ktime_add_safe(time, delta);
> +}

> @@ -241,10 +259,19 @@ static inline ktime_t hrtimer_get_expires(const struct hrtimer *timer)
>  	return timer->_expires;
>  }
>  
> +static inline ktime_t hrtimer_get_softexpires(const struct hrtimer *timer)
> +{
> +	return timer->_expires;
> +}

Somehow the function is called softexpires, but returns the hard expire
time...

>  static inline s64 hrtimer_get_expires_tv64(const struct hrtimer *timer)
>  {
>  	return timer->_expires.tv64;
>  }
> +static inline s64 hrtimer_get_softexpires_tv64(const struct hrtimer *timer)
> +{
> +	return timer->_softexpires.tv64;
> +}
>  
>  static inline s64 hrtimer_get_expires_ns(const struct hrtimer *timer)
>  {

> @@ -1309,7 +1309,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
>  
>  			timer = rb_entry(node, struct hrtimer, node);
>  
> -			if (basenow.tv64 < hrtimer_get_expires_tv64(timer)) {
> +			if (basenow.tv64 < hrtimer_get_softexpires_tv64(timer)) {
>  				ktime_t expires;
>  
>  				expires = ktime_sub(hrtimer_get_expires(timer),

I might be missing something, but this code only looks at the leftmost
timer, and we're indexed on the hard expire time, which might be rather
far to the right of here.

This means that esp for those timers for which we can save most we're
least likely to do so because we'll plain not see them.



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