Re: [Xen-devel] [PATCH 0/3] xen/sched: use new idle scheduler for free cpus

[Juergen Gross <jgross@xxxxxxxx>]

On 13.08.19 17:51, Dario Faggioli wrote:
> On Fri, 2019-08-02 at 15:07 +0200, Juergen Gross wrote:
> > These three patches have been carved out from my core scheduling
> > series
> > as they are sufficiently independent to be applied even without the
> > big
> > series.
> >
> > Without this little series there are messages like the following to
> > be
> > seen on the console when booting with smt=0:
> >
> > (XEN) Adding cpu 1 to runqueue 0
> > (XEN) CPU 1 still not dead...
> > (XEN) CPU 1 still not dead...
> > (XEN) CPU 1 still not dead...
> > (XEN) CPU 1 still not dead...
> >
> > By assigning cpus to Cpupool-0 only after all cpus are up and by not
> > using the more complicated credit2 scheduler for cpus not in any
> > cpupool this situation can simply no longer happen, as parking the
> > not
> > to be started threads is done before.
> And this is not the only problem, solved by this series (or an
> equivalent approach).
>
> Right now, CPUs that are not in any pool, still belong to Pool-0's
> scheduler. This forces us to make, within the scheduler, extra effort
> to avoid actually running vCPUs on those.
>
> In the case of Credit1, this also cause issue to weights
> (re)distribution, as the number of CPUs available to the scheduler is
> wrong.
>
> So, we absolutely want something like this.
>
> This is described in the changelog of commit e7191920261d ("xen:
> credit2: never consider CPUs outside of our cpupool").
>
> Would it be possible to mention this in one of the changelogs of the
> series (patch 3 would be the best place, I think).
Okay.


Juergen

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