linux-kernel - Re: [PATCH] sched: fair: drop useless cpumask_empty() in find_energy_efficient

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8f0c39e3-af68-4f01-94e5-e63ee52864df@linux.ibm.com>
Date: Thu, 11 Sep 2025 12:15:09 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH] sched: fair: drop useless cpumask_empty() in
 find_energy_efficient_cpu()

On 11/09/25 08:04, Yury Norov wrote:
> From: Yury Norov (NVIDIA) <yury.norov@...il.com>
> 
> cpumask_empty() call is O(N) and useless, because the previous
> cpumask_and() returns false for empty 'cpus'.
> 

LGTM

Reviewed-by: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>

Thanks,
Madadi Vineeth Reddy

> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>
> ---
>  kernel/sched/fair.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index b173a059315c..7229339cbb1b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8320,9 +8320,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
>  		int max_spare_cap_cpu = -1;
>  		int fits, max_fits = -1;
>  
> -		cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
> -
> -		if (cpumask_empty(cpus))
> +		if (!cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask))
>  			continue;
>  
>  		/* Account external pressure for the energy estimation */