linux-kernel - Re: [PATCH] sched/fair: Revise comment about lb decision matrix

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Date:   Fri, 15 Apr 2022 01:27:08 +0800
From:   Tao Zhou <tao.zhou@...ux.dev>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: Revise comment about lb decision matrix

On Thu, Apr 14, 2022 at 12:33:06PM +0200,
Dietmar Eggemann wrote:
> On 03/04/2022 19:59, Tao Zhou wrote:
> > If busiest group type is group_misfit_task, the local
> > group type must be group_has_spare according to below
> > code in update_sd_pick_busiest():
> > 
> > if (sgs->group_type == group_misfit_task &&
> >     (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
> >      sds->local_stat.group_type != group_has_spare))
> >          return false;
> > 
> > group type imbalanced and overloaded and fully_busy are filtered in here.
> > misfit and asym are filtered before in update_sg_lb_stats().
> > So, change the decision matrix to:
> > 
> > busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
> > has_spare        nr_idle   balanced   N/A    N/A  balanced   balanced
> > fully_busy       nr_idle   nr_idle    N/A    N/A  balanced   balanced
> > misfit_task      force     N/A        N/A    N/A  *N/A*      *N/A*
> > asym_packing     force     force      N/A    N/A  force      force
> > imbalanced       force     force      N/A    N/A  force      force
> > overloaded       force     force      N/A    N/A  force      avg_load
> > ---
> >  kernel/sched/fair.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 5146163bfabb..5765d96202c7 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -9441,7 +9441,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
> >   * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
> >   * has_spare        nr_idle   balanced   N/A    N/A  balanced   balanced
> >   * fully_busy       nr_idle   nr_idle    N/A    N/A  balanced   balanced
> > - * misfit_task      force     N/A        N/A    N/A  force      force
> > + * misfit_task      force     N/A        N/A    N/A  N/A        N/A
> >   * asym_packing     force     force      N/A    N/A  force      force
> >   * imbalanced       force     force      N/A    N/A  force      force
> >   * overloaded       force     force      N/A    N/A  force      avg_load
> 
> You should put people you find in `./scripts/get_maintainer.pl
> kernel/sched/fair.c` on To/Cc to attract more attention.
> 
> Otherwise, LGTM.
> 
> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>

I will send based on latest rc version..

Thanks,
Tao