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Fri, 10 Apr 2026 06:31:04 +0000 Message-ID: <1519bccf-205c-4687-88ba-8aa601d1a086@intel.com> Date: Fri, 10 Apr 2026 14:30:50 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [Patch v4 01/22] sched/cache: Introduce infrastructure for cache-aware load balancing To: Peter Zijlstra , Tim Chen CC: Ingo Molnar , K Prateek Nayak , "Gautham R . Shenoy" , Vincent Guittot , Juri Lelli , "Dietmar Eggemann" , Steven Rostedt , Ben Segall , Mel Gorman , "Valentin Schneider" , Madadi Vineeth Reddy , Hillf Danton , Shrikanth Hegde , Jianyong Wu , Yangyu Chen , Tingyin Duan , Vern Hao , Vern Hao , Len Brown , Aubrey Li , Zhao Liu , Chen Yu , Adam Li , Aaron Lu , Tim Chen , Josh Don , Gavin Guo , Qais Yousef , Libo Chen , References: <6269a53221b9439b9ca00d18a9d1946fb64d8cff.1775065312.git.tim.c.chen@linux.intel.com> <20260409124110.GA3126523@noisy.programming.kicks-ass.net> <71b4ddab042b805a225eef92b0a9404b20aa2b98.camel@linux.intel.com> <20260409230004.GV2872@noisy.programming.kicks-ass.net> Content-Language: en-US From: "Chen, Yu C" In-Reply-To: <20260409230004.GV2872@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SG2PR04CA0187.apcprd04.prod.outlook.com (2603:1096:4:14::25) 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_|IA1PR11MB8151:EE_ X-MS-Office365-Filtering-Correlation-Id: e259f453-ef68-466c-0cde-08de96cabdb9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016|18002099003|56012099003|22082099003; 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The comment just states we are (doh), but utterly fails to >>> explain why. >> >> The thought was that for a single thread, we will tend to place it >> in same LLC as it was previously running with cache hot. Incurring >> the added cost of tracking its residency in LLC is uneeded. > > Not sure -- the moment it gets migrated away, it will stay away. There > is no force to pull it back, while with cache aware it will try and come > back for a short while -- until it's build an occupancy on the new llc. > Besides Tim's scenario, in the original design, I thought the beneficiary of cache-aware scheduling was mainly multi-threaded processes, where threads share data with each other. Single-threaded processes normally exhibit no data sharing. This check was also introduced to prevent a single process from concentrating excessively on one LLC. Nevertheless, we can omit this check if the user provides hints for such single-threaded workloads, either via prctl or other interfaces in the future. > Anyway, if you want to do this, it needs to be a separate patch. OK, we will move this check into a separate one. thanks, Chenyu