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

[Roman Zippel <zippel@linux-m68k.org>]

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
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