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Later it may be > marked as non-preferred depending on steal time values with > STEAL_MONITOR enabled. > > Signed-off-by: Shrikanth Hegde > --- > include/linux/cpumask.h | 22 ++++++++++++++++++++++ > kernel/cpu.c | 6 ++++++ > kernel/sched/core.c | 5 +++++ > 3 files changed, 33 insertions(+) > > diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h > index 80211900f373..80c5cc13b8ad 100644 > --- a/include/linux/cpumask.h > +++ b/include/linux/cpumask.h > @@ -1296,6 +1296,28 @@ static __always_inline bool cpu_dying(unsigned int cpu) > > #endif /* NR_CPUS > 1 */ > > +/* > + * All related wrappers kept together to avoid too many ifdefs > + * See Documentation/scheduler/sched-arch.rst for details > + */ > +#ifdef CONFIG_PARAVIRT > +extern struct cpumask __cpu_preferred_mask; > +#define cpu_preferred_mask ((const struct cpumask *)&__cpu_preferred_mask) > +#define set_cpu_preferred(cpu, preferred) assign_cpu((cpu), &__cpu_preferred_mask, (preferred)) > + > +static __always_inline bool cpu_preferred(unsigned int cpu) > +{ > + return cpumask_test_cpu(cpu, cpu_preferred_mask); > +} > +#else > +static __always_inline bool cpu_preferred(unsigned int cpu) > +{ > + return true; > +} This doesn't look consistent, probably not correct. What if I pass an offline CPU here? Is it still preferred? Later you say that preferred CPU is online + STEAL-approved one. So in non-paravirtualized case, I believe, you should consider that only online CPUs are preferred. What about dying CPUs? Can they be preferred too? At least, please run cpumask_check() on the argument. There's a top-comment describing all the system cpumasks. Except for cpu_dying, it's nice and complete. Can you describe your new creature there? Finally, I don't think that __cpu_preferred_mask should depend on PARAVIRT config. Consider cpu_present_mask. It mirrors cpu_possible_mask if hotplug is disabled, but it's still a real mask even in that case. The way you're doing it, you spread CONFIG_PARAVIRT ifdefery pretty much anywhere where people might want to use this new mask for anything except for testing a bit. Thanks, Yury > +static __always_inline void set_cpu_preferred(unsigned int cpu, bool preferred) { } > +#endif > + > #define cpu_is_offline(cpu) unlikely(!cpu_online(cpu)) > > #if NR_CPUS <= BITS_PER_LONG > diff --git a/kernel/cpu.c b/kernel/cpu.c > index bc4f7a9ba64e..2d4d037680d4 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -3137,6 +3137,12 @@ void set_cpu_online(unsigned int cpu, bool online) > if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask)) > atomic_dec(&__num_online_cpus); > } > + > + /* > + * An online CPU is by default assumed to be preferred > + * Unitl STEAL_MONITOR changes it > + */ > + set_cpu_preferred(cpu, online); > } > > /* > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index f351296922ac..7ea05a7a717b 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -11228,3 +11228,8 @@ void sched_change_end(struct sched_change_ctx *ctx) > p->sched_class->prio_changed(rq, p, ctx->prio); > } > } > + > +#ifdef CONFIG_PARAVIRT > +struct cpumask __cpu_preferred_mask __read_mostly; > +EXPORT_SYMBOL(__cpu_preferred_mask); > +#endif > -- > 2.47.3