linux-kernel - Re: [ck] Re: SD still better than CFS for 3d ?(was Re: 2.6.23-rc1)

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Message-ID: <20070731163646.GA15013@elte.hu>
Date:	Tue, 31 Jul 2007 18:36:46 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Miguel Figueiredo <elmig@...ianpt.org>
Cc:	ck@....kolivas.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [ck] Re: SD still better than CFS for 3d ?(was Re: 2.6.23-rc1)


* Miguel Figueiredo <elmig@...ianpt.org> wrote:

> > this is what CFS does:
> >
> >   static void yield_task_fair(struct rq *rq, struct task_struct *p)
> >   {
> >           struct cfs_rq *cfs_rq = task_cfs_rq(p);
> >           u64 now = __rq_clock(rq);
> >
> >           /*
> >            * Dequeue and enqueue the task to update its
> >            * position within the tree:
> >            */
> >           dequeue_entity(cfs_rq, &p->se, 0, now);
> >           enqueue_entity(cfs_rq, &p->se, 0, now);
> >   }
> >
> > 	Ingo
> 
> So the difference from mainline (2.6.22) is that now you removed 
> requeue_task(), is that it?

No - I renamed requeue_task() to current->sched_class->yield_task(), 
which does this for SCHED_OTHER:

           /*
            * Dequeue and enqueue the task to update its
            * position within the tree:
            */
           dequeue_entity(cfs_rq, &p->se, 0, now);
           enqueue_entity(cfs_rq, &p->se, 0, now);

and this for RT tasks:

           static void
           yield_task_rt(struct rq *rq, struct task_struct *p)
           {
                   requeue_task_rt(rq, p);
           }

a dequeue+enqueue _is_ a requeue ...

	Ingo
-
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