Re: [PATCH] Call get_time() only when necessary in run_hrtimer_queue

Eric Dumazet
2006-03-28T17:39:14Z

Dimitri Sivanich a écrit :
>
> The hrtimer work in -mm does improve on the situation, although there
> appears to be some occasional cache line contention for xtime. The
> following patch (which is similiar to my previously submitted patch)
> is applicable to 2.6.16-mm1 and does take care of at least a good
> portion of that.

I am not sure your patch is correct.

>
> Index: linux/kernel/hrtimer.c
> ===================================================================
> --- linux.orig/kernel/hrtimer.c 2006-03-27 09:43:40.000000000 -0600
> +++ linux/kernel/hrtimer.c 2006-03-27 12:35:47.416054373 -0600
> @@ -604,14 +604,17 @@ int hrtimer_get_res(const clockid_t whic
> */
> static inline void run_hrtimer_queue(struct hrtimer_base *base)
> {
> - struct rb_node *node;
> + struct rb_node *node = base->first;
> +
> + if (!node)
> + return;
>
> if (base->get_softirq_time)
> base->softirq_time = base->get_softirq_time();
>
> spin_lock_irq(&base->lock);
>
> - while ((node = base->first)) {
> + while (node) {

Are you sure of this change ?

base->first may have changed just before you locked the base->lock
(spin_lock_irq(&base->lock);)

Eric