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Fri, 15 May 2026 12:29:38 +0000 Message-ID: Date: Fri, 15 May 2026 20:29:28 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/4] sched/fair: Check CPU capacity before comparing group types during load balance To: Ricardo Neri CC: "Rafael J. Wysocki" , Len Brown , Dietmar Eggemann , Juri Lelli , Vincent Guittot , , , Steven Rostedt , Ben Segall , Valentin Schneider , Mel Gorman , Tim C Chen , Christian Loehle , Peter Zijlstra , Ingo Molnar , "Barry Song" References: <20260514-rneri-fix-cas-clusters-v3-0-0037869554bd@linux.intel.com> <20260514-rneri-fix-cas-clusters-v3-1-0037869554bd@linux.intel.com> Content-Language: en-US From: "Chen, Yu C" In-Reply-To: <20260514-rneri-fix-cas-clusters-v3-1-0037869554bd@linux.intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: TPYP295CA0006.TWNP295.PROD.OUTLOOK.COM (2603:1096:7d0:9::16) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR11MB6020:EE_|SJ0PR11MB4960:EE_ X-MS-Office365-Filtering-Correlation-Id: e9649a72-a0ef-4283-8114-08deb27da163 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|1800799024|22082099003|18002099003|56012099003|11063799003|4143699003; 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> > + /* > + * Candidate sg has no more than one task per CPU and has higher > + * per-CPU capacity. Migrating tasks to less capable CPUs may harm > + * throughput. Maximize throughput, power/energy consequences are not > + * considered. > + * > + * Systems with SMT are unaffected, as asymmetric capacity is not set > + * in such cases. > + */ Does "SMT" here imply that group_smt_balance is unaffected? Regardless of whether we move the check earlier, this seems to already be guaranteed by the fact that the check only applies to sgs->group_type <= group_fully_busy, which does not include group_smt_balance. In other words, SD_ASYM_CPUCAPACITY is not the only gatekeeper. Other than that, the change looks good to me,Reviewed-by: Chen Yu thanks, Chenyu > + if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && > + (sgs->group_type <= group_fully_busy) && > + (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu)))) > + return false; > +