linux-kernel - Re: [PATCH] sched/topology: Align group flags when removing degenerate domain

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Date:   Thu, 13 Jul 2023 14:35:17 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     Chen Yu <yu.c.chen@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ingo Molnar <mingo@...hat.com>
CC:     <yangyicong@...ilicon.com>, Ricardo Neri <ricardo.neri@...el.com>,
        Tim Chen <tim.c.chen@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/topology: Align group flags when removing
 degenerate domain

On 2023/7/13 9:31, Chen Yu wrote:
> The flags of the child of a given scheduling domain are used to initialize
> the flags of its scheduling groups. When the child of a scheduling domain
> is degenerated, the flags of its local scheduling group need to be updated
> to align with the flags of its new child domain.
> 
> The flag SD_SHARE_CPUCAPACITY was aligned in
> Commit bf2dc42d6beb ("sched/topology: Propagate SMT flags when removing degenerate domain").
> Further generalize this alignment so other flags can be used later, such as
> in cluster-based task wakeup. [1]

Currently I only update the cluster flags on my current testing branch. It'll be even better to
align all flags for possible usage. Will rebase on this one.

> 
> Link: https://lore.kernel.org/lkml/20230530115527.GC156198@hirez.programming.kicks-ass.net #1
> Suggested-by: Ricardo Neri <ricardo.neri@...el.com>
> Reported-by: Yicong Yang <yangyicong@...wei.com>
> Closes: https://lore.kernel.org/lkml/ce714341-af58-2522-69a8-321f02c82893@huawei.com/
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>

Reviewed-by: Yicong Yang <yangyicong@...ilicon.com>

> ---
>  kernel/sched/topology.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index d3a3b2646ec4..ff02d7deec0c 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -722,8 +722,7 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
>  
>  			if (parent->parent) {
>  				parent->parent->child = tmp;
> -				if (tmp->flags & SD_SHARE_CPUCAPACITY)
> -					parent->parent->groups->flags |= SD_SHARE_CPUCAPACITY;
> +				parent->parent->groups->flags = tmp->flags;
>  			}
>  
>  			/*
>