Re: [ANNOUNCE/RFC] Really Simple Really Fair Scheduler

Roman Zippel
2007-09-03T19:55:16Z

Hi,

On Mon, 3 Sep 2007, Ingo Molnar wrote:

> My next question then is about this code of yours in the wakeup path:
>
> +static void
> +enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
> +{
> + kclock_t min_time;
> +
> + verify_queue(cfs_rq, cfs_rq->curr != se, se);
> + min_time = get_time_avg(cfs_rq) - se->req_weight_inv;
> + if ((kclock_t)(se->time_norm - min_time) < 0)
> + se->time_norm = min_time;
>
> why do you only use the "min_time" if the pre-sleep time_norm is smaller
> than the min_time? Here 'min_time' is close to the current average.

It's a variation of the sleeper bonus. Let's assume two running tasks
which have been running for 95ms and 105ms and a time slice of 10ms, the
average is thus 100ms. If the new task has been sleeping for a while it
starts at 90ms, if the task had been running lately it doesn't get this
bonus again.

> Shouldnt here the woken up task be set to the average time, like i did
> it in the crude prototype:
>
> + se->exec_runtime = avg_exec_runtime(cfs_rq);

That would be equivalent to simply clearing wait_runtime in CFS.

bye, Roman