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Date:   Fri, 13 Dec 2019 10:43:29 +0530
From:   Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To:     Cheng Jian <cj.chengjian@huawei.com>
Cc:     mingo@kernel.org, peterz@infradead.org,
        linux-kernel@vger.kernel.org, chenwandun@huawei.com,
        xiexiuqi@huawei.com, liwei391@huawei.com, huawei.libin@huawei.com,
        bobo.shaobowang@huawei.com, juri.lelli@redhat.com,
        vincent.guittot@linaro.org
Subject: Re: [PATCH v2] sched/fair: Optimize select_idle_cpu
Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
References: <20191213024530.28052-1-cj.chengjian@huawei.com>
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* Cheng Jian <cj.chengjian@huawei.com> [2019-12-13 10:45:30]:

> Fixes: 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()")
> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
> ---
>  kernel/sched/fair.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 08a233e97a01..d48244388ce9 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5828,6 +5828,7 @@ static inline int select_idle_smt(struct task_struct *p, int target)
>   */
>  static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
>  {
> +	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
>  	struct sched_domain *this_sd;
>  	u64 avg_cost, avg_idle;
>  	u64 time, cost;
> @@ -5859,11 +5860,11 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
>  
>  	time = cpu_clock(this);
>  
> -	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
> +	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
> +
> +	for_each_cpu_wrap(cpu, cpus, target) {
>  		if (!--nr)
>  			return si_cpu;
> -		if (!cpumask_test_cpu(cpu, p->cpus_ptr))
> -			continue;
>  		if (available_idle_cpu(cpu))
>  			break;
>  		if (si_cpu == -1 && sched_idle_cpu(cpu))
Looks good to me.

Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

-- 
Thanks and Regards
Srikar Dronamraju