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Subject: Re: [PATCH v3 5/7] sched/fair: Employ capacity_greater() throughout
 load_balance()
To:     Valentin Schneider <valentin.schneider@arm.com>,
        linux-kernel@vger.kernel.org
Cc:     Qais Yousef <qais.yousef@arm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Quentin Perret <qperret@google.com>,
        Pavan Kondeti <pkondeti@codeaurora.org>,
        Rik van Riel <riel@surriel.com>
References: <20210311120527.167870-1-valentin.schneider@arm.com>
 <20210311120527.167870-6-valentin.schneider@arm.com>
From:   Chandra Sekhar Lingutla <clingutla@codeaurora.org>
Message-ID: <3f5c3f78-0d0d-af89-56d7-cb9a91b98898@codeaurora.org>
Date:   Wed, 31 Mar 2021 17:05:06 +0530
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Hi Valentin,

The reduced margin is helping our platforms, Please feel free to add my 
tested-by tag:

Tested-by:  Lingutla Chandrasekhar <clingutla@codeaurora.org>

On 3/11/2021 5:35 PM, Valentin Schneider wrote:
> While at it, replace group_smaller_{min, max}_cpu_capacity() with
> comparisons of the source group's min/max capacity and the destination
> CPU's capacity.
>
> Reviewed-by: Qais Yousef <qais.yousef@arm.com>
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
> ---
>   kernel/sched/fair.c | 33 ++++-----------------------------
>   1 file changed, 4 insertions(+), 29 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index ddb2ab3edf6d..1e8a242cd1f7 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8350,26 +8350,6 @@ group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
>   	return false;
>   }
>   
> -/*
> - * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller
> - * per-CPU capacity than sched_group ref.
> - */
> -static inline bool
> -group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
> -{
> -	return fits_capacity(sg->sgc->min_capacity, ref->sgc->min_capacity);
> -}
> -
> -/*
> - * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller
> - * per-CPU capacity_orig than sched_group ref.
> - */
> -static inline bool
> -group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
> -{
> -	return fits_capacity(sg->sgc->max_capacity, ref->sgc->max_capacity);
> -}
> -
>   static inline enum
>   group_type group_classify(unsigned int imbalance_pct,
>   			  struct sched_group *group,
> @@ -8518,15 +8498,10 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>   	if (!sgs->sum_h_nr_running)
>   		return false;
>   
> -	/*
> -	 * Don't try to pull misfit tasks we can't help.
> -	 * We can use max_capacity here as reduction in capacity on some
> -	 * CPUs in the group should either be possible to resolve
> -	 * internally or be covered by avg_load imbalance (eventually).
> -	 */
> +	/* Don't try to pull misfit tasks we can't help */
>   	if (static_branch_unlikely(&sched_asym_cpucapacity) &&
>   	    sgs->group_type == group_misfit_task &&
> -	    (!group_smaller_max_cpu_capacity(sg, sds->local) ||
> +	    (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
>   	     sds->local_stat.group_type != group_has_spare))
>   		return false;
>   
> @@ -8610,7 +8585,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>   	 */
>   	if (sd_has_asym_cpucapacity(env->sd) &&
>   	    (sgs->group_type <= group_fully_busy) &&
> -	    (group_smaller_min_cpu_capacity(sds->local, sg)))
> +	    (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
>   		return false;
>   
>   	return true;
> @@ -9410,7 +9385,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
>   		 * average load.
>   		 */
>   		if (sd_has_asym_cpucapacity(env->sd) &&
> -		    capacity_of(env->dst_cpu) < capacity &&
> +		    !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
>   		    nr_running == 1)
>   			continue;
>