On Fri, 19 Jul 2019 at 15:22, Peter Zijlstra <pet...@infradead.org> wrote:
>
> On Fri, Jul 19, 2019 at 09:58:23AM +0200, Vincent Guittot wrote:
> > enum group_type {
> > - group_other = 0,
> > + group_has_spare = 0,
> > + group_fully_busy,
> > group_misfit_task,
> > + group_asym_capacity,
> > group_imbalanced,
> > group_overloaded,
> > };
>
> The order of this group_type is important, maybe add a few words on how
> this order got to be.
Yes, I will
>
> > static inline enum
> > -group_type group_classify(struct sched_group *group,
> > +group_type group_classify(struct lb_env *env,
> > + struct sched_group *group,
> > struct sg_lb_stats *sgs)
> > {
> > - if (sgs->group_no_capacity)
> > + if (group_is_overloaded(env, sgs))
> > return group_overloaded;
> >
> > if (sg_imbalanced(group))
> > @@ -7953,7 +7975,13 @@ group_type group_classify(struct sched_group *group,
> > if (sgs->group_misfit_task_load)
> > return group_misfit_task;
> >
> > - return group_other;
> > + if (sgs->group_asym_capacity)
> > + return group_asym_capacity;
> > +
> > + if (group_has_capacity(env, sgs))
> > + return group_has_spare;
> > +
> > + return group_fully_busy;
> > }
>
> OCD is annoyed that this function doesn't have the same / reverse order
> of the one in the enum.
I will reorder them
>
> > @@ -8070,7 +8111,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
> > */
> > if (sgs->group_type == group_misfit_task &&
> > (!group_smaller_max_cpu_capacity(sg, sds->local) ||
> > - !group_has_capacity(env, &sds->local_stat)))
> > + sds->local_stat.group_type != group_has_spare))
> > return false;
> >
> > if (sgs->group_type > busiest->group_type)
> > @@ -8079,11 +8120,18 @@ static bool update_sd_pick_busiest(struct lb_env
> > *env,
> > if (sgs->group_type < busiest->group_type)
> > return false;
>
> from reading the patch it wasn't obvious that at this point
I will add a comment to mention this
> sgs->group_type == busiest->group_type, and I wondered if
> busiest->avg_load below was pointing to garbage, it isn't.
>
> > - if (sgs->avg_load <= busiest->avg_load)
> > + /* Select the overloaded group with highest avg_load */
> > + if (sgs->group_type == group_overloaded &&
> > + sgs->avg_load <= busiest->avg_load)
> > + return false;
> > +
> > + /* Prefer to move from lowest priority CPU's work */
> > + if (sgs->group_type == group_asym_capacity && sds->busiest &&
> > + sched_asym_prefer(sg->asym_prefer_cpu,
> > sds->busiest->asym_prefer_cpu))
> > return false;
> >
> > if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
> > - goto asym_packing;
> > + goto spare_capacity;
> >
> > /*
> > * Candidate sg has no more than one task per CPU and
>
> Can we do a switch (sds->group_type) here? it seems to have most of them
> listed.
I will have a look but I'm afraid that the
if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
prevents us to get something readbale
