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Wed, 16 Jul 2025 15:56:39 +0000 Message-ID: <5e9789ae-9a2d-4c95-a1c3-db489d132559@intel.com> Date: Wed, 16 Jul 2025 23:56:30 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] sched/fair: bump sd->max_newidle_lb_cost when newidle balance fails To: Chris Mason , Chris Mason CC: , , , , , , kernel test robot References: <202507150846.538fc133-lkp@intel.com> <10abe013-98d6-4080-ac43-0f1e02aa41f9@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: SG2PR01CA0140.apcprd01.prod.exchangelabs.com (2603:1096:4:8f::20) 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_|CY5PR11MB6161:EE_ X-MS-Office365-Filtering-Correlation-Id: ff38cd15-1f0d-4b40-b91e-08ddc481599a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016; 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It seems that some workloads >> do not like newlyidle balance, like schbench, which is short duration >> task. While other workloads want the newidle balance to pull at its best >> effort, like unixbench shell test case. >> Just wonder if we can check the sched domain's average utilization to >> decide how hard we should trigger the newly idle balance, or can we check >> the overutilized flag to decide whether we should launch the >> new idle balance, something I was thinking of: > > Thanks for looking at this. > >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 9e24038fa000..6c7420ed484e 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -13759,7 +13759,8 @@ static int sched_balance_newidle(struct rq >> *this_rq, struct rq_flags *rf) >>         sd = rcu_dereference_check_sched_domain(this_rq->sd); >> >>         if (!get_rd_overloaded(this_rq->rd) || >> -           (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) { >> +           (sd && this_rq->avg_idle < sd->max_newidle_lb_cost && >> +            !READ_ONCE(this_rq->rd->overutilized))) { >> >>                 if (sd) >>                         update_next_balance(sd, &next_balance); >> > > > Looking at rd->overutilized, I think we only set it when > sched_energy_enabled(). I'm not sure if that's true often enough to use > as a fix for hackbench? > OK, overutilized is only used for EAS. I just had a try but can not reproduce this issue on a 240 CPUs system using unixbench: ./Run shell1 -i 30 -c 240 will need to double check with lkp/0day to figure out. thanks, Chenyu > -chris >