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From:   Tao Zhou <tao.zhou@linux.dev>
To:     linux-kernel@vger.kernel.org, tao.zhou@linux.dev
Subject: [PATCH] sched/fair: Revise comment about lb decision matrix
Date:   Mon,  4 Apr 2022 01:59:46 +0800
Message-Id: <20220403175946.7323-1-tao.zhou@linux.dev>
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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