Re: [PATCH v4 04/20] cpumask: Introduce cpu_preferred_mask

[Shrikanth Hegde]

Hi Yury.

> > +void set_cpu_preferred(unsigned int cpu, bool preferred)
> > +{
> > +	if (!IS_ENABLED(CONFIG_PREFERRED_CPU))
> > +		return;
> > +
> > +	assign_cpu((cpu), &__cpu_preferred_mask, (preferred));
> > +}
>
> set_cpu_xxx() is a macro on purpose - it improves code generation
> quite a lot. See 5c563ee90a22d. Can you keep set_cpu_preferred aligned
> with the other set_cpu(), i.e. make it a macro?

Ok. only reason was to avoid ifdeffery there.

you mean below?

#ifdef CONFIG_PREFERRED_CPU
#else
#endif


 
> > +
> >   /*
> >    * Activate the first processor.
> >    */
> > @@ -3164,6 +3177,7 @@ void __init boot_cpu_init(void)
> >   	/* Mark the boot cpu "present", "online" etc for SMP and UP case */
> >   	set_cpu_online(cpu, true);
> >   	set_cpu_active(cpu, true);
> > +	set_cpu_preferred(cpu, true);
> >   	set_cpu_present(cpu, true);
> >   	set_cpu_possible(cpu, true);
> >   
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 2f4530eb543f..9e16946c9d62 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -8685,6 +8685,9 @@ int sched_cpu_activate(unsigned int cpu)
> >   	 */
> >   	sched_set_rq_online(rq, cpu);
> >   
> > +	/* preferred is subset of active and follows its state */
> > +	set_cpu_preferred(cpu, true);
>
> Did you put it at the end of the function on purpose? If yes, please
> add a comment. If no, I'd prefer to have it immediately after
> set_cpu_active().

        /*
         * Put the rq online, if not already. This happens:
         *
         * 1) In the early boot process, because we build the real domains
         *    after all CPUs have been brought up.

         * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
         *    domains.
         */
        sched_set_rq_online(rq, cpu);


This was the reason. I wanted active related functionality to complete.

> > +
> >   	return 0;
> >   }
> >   
> > @@ -8698,6 +8701,8 @@ int sched_cpu_deactivate(unsigned int cpu)
> >   	if (ret)
> >   		return ret;
> >   
> > +	set_cpu_preferred(cpu, false);
> > +
> >   	/*
> >   	 * Remove CPU from nohz.idle_cpus_mask to prevent participating in
> >   	 * load balancing when not active
> > --
> > 2.47.3