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Wed, 10 Dec 2025 14:06:02 +0000 Message-ID: <5613f6eb-7319-464e-9723-2d82ddaca0c9@intel.com> Date: Wed, 10 Dec 2025 23:05:33 +0900 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 09/23] sched/cache: Count tasks prefering destination LLC in a sched group 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 , References: <1eb6a231ec82b37483208983f0cf10eec823ec9d.1764801860.git.tim.c.chen@linux.intel.com> <20251210125233.GT3707891@noisy.programming.kicks-ass.net> Content-Language: en-US From: "Chen, Yu C" In-Reply-To: <20251210125233.GT3707891@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: KUZPR04CA0020.apcprd04.prod.outlook.com (2603:1096:d10:25::10) 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_|DM4PR11MB7373:EE_ X-MS-Office365-Filtering-Correlation-Id: 0ec5ea1e-c774-40e0-38a9-08de37f5408a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014; 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LLC0 has 3 tasks preferring LLC3, LLC1 has >> 2, and LLC2 has 1. LLC0, having the most tasks preferring LLC3, is >> selected as the busiest source to pick tasks from. >> >> Within a source LLC, the total number of tasks preferring a destination >> LLC is computed by summing counts across all CPUs in that LLC. For >> instance, if LLC0 has CPU0 with 2 tasks and CPU1 with 1 task preferring >> LLC3, the total for LLC0 is 3. >> >> These statistics allow the load balancer to choose tasks from source >> sched groups that best match their preferred LLCs. >> >> Signed-off-by: Tim Chen >> --- >> >> Notes: >> v1->v2: >> Convert nr_pref_llc array in sg_lb_stats to a single >> variable as only the dst LLC stat is needed. >> (K Prateek Nayak) >> >> kernel/sched/fair.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index b0e87616e377..4d7803f69a74 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -10445,6 +10445,9 @@ struct sg_lb_stats { >> unsigned int nr_numa_running; >> unsigned int nr_preferred_running; >> #endif >> +#ifdef CONFIG_SCHED_CACHE >> + unsigned int nr_pref_llc; >> +#endif > > At this point I have to note that rq->nr_pref_llc seems like a horrible > misnomer, for it being an array, and not an actual number like the > naming suggests. In the v2 it seems that rq->nr_pref_llc is not an array anymore, it indicates the number of tasks that want to be migrated to the env->dst_cpu (dst_llc), because these tasks' preferred LLC are env->dst_cpu(dst_llc). Maybe renaming it to rq->nr_pref_dst_llc? thanks, Chenyu