linux-kernel - Re: [ANNOUNCE/RFC] Really Simple Really Fair Scheduler

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Message-ID: <20070903192050.GA29049@elte.hu>
Date:	Mon, 3 Sep 2007 21:20:50 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Roman Zippel <zippel@...ux-m68k.org>
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org,
	Mike Galbraith <efault@....de>
Subject: Re: [ANNOUNCE/RFC] Really Simple Really Fair Scheduler


* Roman Zippel <zippel@...ux-m68k.org> wrote:

> On Mon, 3 Sep 2007, Ingo Molnar wrote:
> 
> > If this basic model is correct, we can look further.
> 
> The basic model is correct insofar I use an absolute time instead of a 
> relative time, but it's not the essence of my math, so I don't quite 
> understand the point of this exercise.

thanks. (and i did not claim nor do i want to claim this to be the 
essence of your efforts - it is very clear from your mails where your 
focus is.)

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. 
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);

(and lets again only consider the special case of only having nice-0 
tasks.)

Or is it set in a similar way as my prototype does, and i missed some 
detail why that branch is there?

	Ingo
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