[PATCH] sched/fair: Revise comment about lb decision matrix

[PATCH] sched/fair: Revise comment about lb decision matrix

[Tao Zhou]

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
-- 
2.35.1

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

[Dietmar Eggemann]

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@arm.com>

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

[Tao Zhou]

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@arm.com>

I will send based on latest rc version..

Thanks,
Tao