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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by CY4PEPF0000EE3B.mail.protection.outlook.com (10.167.242.14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9115.13 via Frontend Transport; Thu, 11 Sep 2025 06:45:07 +0000 Received: from satlexmb10.amd.com (10.181.42.219) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Wed, 10 Sep 2025 23:45:02 -0700 Received: from satlexmb07.amd.com (10.181.42.216) by satlexmb10.amd.com (10.181.42.219) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Wed, 10 Sep 2025 23:45:02 -0700 Received: from [172.31.178.191] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Wed, 10 Sep 2025 23:44:58 -0700 Message-ID: <1456057a-6289-491a-a776-84856226d97b@amd.com> Date: Thu, 11 Sep 2025 12:14:57 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] sched: fair: drop useless cpumask_empty() in find_energy_efficient_cpu() To: Yury Norov , Ingo Molnar , "Peter Zijlstra" , Juri Lelli , "Vincent Guittot" , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , References: <20250911023426.457745-1-yury.norov@gmail.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20250911023426.457745-1-yury.norov@gmail.com> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Sep 2025 06:45:07.5438 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 98fc312f-8270-44ea-2024-08ddf0febf2e X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000EE3B.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV5PR12MB9756 Hello Yury, On 9/11/2025 8:04 AM, Yury Norov wrote: > From: Yury Norov (NVIDIA) > > cpumask_empty() call is O(N) and useless, because the previous > cpumask_and() returns false for empty 'cpus'. I agree. Please feel free to include: Reviewed-by: K Prateek Nayak > > Signed-off-by: Yury Norov (NVIDIA) > --- > 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 */ -- Thanks and Regards, Prateek