Re: [PATCH 11/39] autonuma: CPU follow memory algorithm

[Rik van Riel]

On 03/26/2012 02:25 PM, Peter Zijlstra wrote:
> On Mon, 2012-03-26 at 19:45 +0200, Andrea Arcangeli wrote:
> > @@ -3220,6 +3214,8 @@ need_resched:
> >
> >          post_schedule(rq);
> >
> > +       sched_autonuma_balance();
> > +
> >          sched_preempt_enable_no_resched();
> >          if (need_resched())
> >                  goto need_resched;
>
> I already told you, this isn't ever going to happen. You do _NOT_ put a
> for_each_online_cpu() loop in the middle of schedule().

Agreed, it looks O(N), but because every CPU will be calling
it its behaviour will be O(N^2) and has the potential to
completely break systems with a large number of CPUs.

Finding a lower overhead way of doing the balancing does not
seem like an unsurmountable problem.

> You also do not call stop_one_cpu(migration_cpu_stop) in schedule to
> force migrate the task you just scheduled to away from this cpu. That's
> retarded.
>
> Nacked-by: Peter Zijlstra<a.p.zijlstra@xxxxxxxxx>


--
All rights reversed
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/