Re: [PATCH 6/6] sched: disabled rt-bandwidth by default

Andi Kleen
2008-08-28T16:30:51Z

On Thu, Aug 28, 2008 at 06:25:48PM +0200, Ingo Molnar wrote:
>
> * Max Krasnyansky <maxk@qualcomm.com> wrote:
>
> > Andi Kleen wrote:
> >> On Thu, Aug 28, 2008 at 01:19:13PM +0200, Peter Zijlstra wrote:
> >>> On Thu, 2008-08-28 at 13:09 +0200, Andi Kleen wrote:
> >>>>> Even if the system has multiple CPUs, and even if just a single CPU is
> >>>>> fully utilized by an RT task, without the rt-limit the system will still
> >>>>> lock up in practice due to various other factors: workqueues and tasks
> >>>>> being 'stuck' on CPUs that host an RT hog.
> >>>> The load balancer will not notice that a particular CPU is busy
> >>>> with real time tasks?
> >>> Not currently, working on that though.
> >>
> >> I wonder if it would make sense to break affinities in extreme case?
> >> With that even the workqueues would work again.
> >
> > Please lets not break affinity :).
>
> correct, breaking affinity is a rather stupid idea.

Ok let's remove cpu hotunplug then. Probably nobody uses it anyways @)

Seriously cpu affinity on all non BP CPU is currently broken on every
suspend to RAM, doing it in a few more cases when it makes the system
more robust is unlikely to hurt anybody.

-Andi

--
ak@linux.intel.com