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Fri, 16 Oct 2026 08:01:45 +0000 Message-ID: Date: Fri, 16 Oct 2026 16:01:33 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] sched/numa: Add per-process automatic NUMA balancing control To: Yafang Shao CC: Tim Chen , "David Hildenbrand (Red Hat)" , , Li Zhe , , , , , , , , , , , , , , , , , References: <20260908122446.56708-1-lizhe.67@bytedance.com> <807eb0e80c76c3ccb85024b360bd47ace201931b.camel@linux.intel.com> Content-Language: en-US From: "Chen, Yu C" In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SI2PR02CA0024.apcprd02.prod.outlook.com (2603:1096:4:195::18) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR11MB6020:EE_|SA3PR11MB722019:EE_ X-MS-Office365-Filtering-Correlation-Id: 259dff7d-b31a-45b3-48a8-08df2b5bb8d7 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|366016|1800799024|376014|23010399003|56012099006|4143699003|11063799006|10067099003|18002099003|22082099003; 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Enabling cache-aware for A1 and A2 might not help in this case. >> >> Suppose threads in A1 and threads in A2 belong to the same process Pa, >> this reminds me of the cgroup bpf NUMA balancing case: after enabling >> NUMA balancing for A1 but not setting it for A2, what would be the final >> NUMA balancing decision for process Pa, is it enabled or disabled? >> The NUMA balancing scan/invalid seems to be per process, so if we change >> the setting of its threads, the whole process will be impacted. Or maybe >> we should not enable NUMA balancing for threaded cgroups? Anyway I haven't >> digged into your cgroup bpf patch set yet, let me try to look at it. > > cgroup NUMAB works the same way: the setting is per cgroup and opt-in. > For Pa in your example, since its threads spread across A1 and A2, you > would enable it on both — enabling it on only one of them is not > meaningful. > I see. I haven't yet digged into your code, is there a per cgroup flag cgroup.numab.enabled? Would there be a logic in the kernel, when A1.numab.enabled is written to true, the kernel detects all the other cgroups {X} that contains threads share the same mm_struct as A1's threads/tasks, and then update {X}'s numab.enabled to the same value as A1, to keep consistency? In summary, if threads are spread cross different cgroups, when you set the enable flag for 1 cgroup, will the kernel iterates all the other cgroups to update their flags as well? Or leverage userspace to do that? thanks, Chenyu