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

Ingo Molnar
2007-07-31T16:37:41Z

* Miguel Figueiredo <elmig@debianpt.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