Re: [Xen-devel] [PATCH v6 01/20] xen/sched: add code to sync scheduling of all vcpus of a sched unit

[Julien Grall <julien.grall@xxxxxxx>]

Hi Juergen,

On 10/2/19 2:56 PM, Jürgen Groß wrote:
> On 02.10.19 09:27, Juergen Gross wrote:
> > When switching sched units synchronize all vcpus of the new unit to be
> > scheduled at the same time.
> >
> > A variable sched_granularity is added which holds the number of vcpus
> > per schedule unit.
> >
> > As tasklets require to schedule the idle unit it is required to set the
> > tasklet_work_scheduled parameter of do_schedule() to true if any cpu
> > covered by the current schedule() call has any pending tasklet work.
> >
> > For joining other vcpus of the schedule unit we need to add a new
> > softirq SCHED_SLAVE_SOFTIRQ in order to have a way to initiate a
> > context switch without calling the generic schedule() function
> > selecting the vcpu to switch to, as we already know which vcpu we
> > want to run. This has the other advantage not to loose any other
> > concurrent SCHEDULE_SOFTIRQ events.
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
> > Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
> Julien gave is Acked-by via IRC.
FAOD, this is assuming patch #8 is going to be fixed to prevent a latent 
bug when context_switch() is returning (such as on Arm).
Cheers,

--
Julien Grall

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