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Mon, 19 Oct 2026 15:44:39 +0000 Date: Mon, 19 Oct 2026 23:31:40 +0800 From: Chen Yu To: Tony Luck CC: Fenghua Yu , Reinette Chatre , Maciej Wieczor-Retman , Peter Newman , James Morse , Babu Moger , "Drew Fustini" , Dave Martin , "David E Box" , , Christoph Hellwig , , Subject: Re: [PATCH v13 10/25] fs/resctrl: Remove redundant calls to resctrl_mon_capable() Message-ID: References: <20260928221509.68002-1-tony.luck@intel.com> <20260928221509.68002-11-tony.luck@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260928221509.68002-11-tony.luck@intel.com> X-ClientProxiedBy: SG2P153CA0001.APCP153.PROD.OUTLOOK.COM (2603:1096::11) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR11MB6020:EE_|IA1PR11MB8786:EE_ X-MS-Office365-Filtering-Correlation-Id: e8c73b89-05d1-43ec-0c56-08df2df7e2bd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|23010399003|1800799024|6133799003|10067099003|22082099003|18002099003|4143699003|5023799004|11063799006|56012099006; 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It does this by scanning all resources. > > Redundant calls to resctrl_mon_capable() in hot code paths should > be eliminated. There are two prime examples: > > 1) mbm_handle_overflow() > This function is called once per second from worker threads running on > each L3 domain. resctrl_mon_capable() is clearly redundant because worker > threads are only created if the MBM monitoring feature is enabled. > > 2) is_rmid_match() > This is called for every task on the system so making it less expensive is > appealing. Nit: since patch 7 turns resctrl_mon_capable() into a resource scan and this patch then drops it, would it be worth moving this patch before patch 7 so there's no intermediate window between these two commits where these callers pay the extra cost? thanks, Chenyu > resctrl_mon_capable() is redundant because the function also > checks "r->type == RDTMON_GROUP" and this type of group can only be created > on systems that support monitoring. > > Remove the call to resctrl_mon_capable() from each of these functions. > > Signed-off-by: Tony Luck