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Tue, 1 Sep 2026 21:14:04 +0000 Date: Tue, 1 Sep 2026 14:14:02 -0700 From: "Luck, Tony" To: Babu Moger CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v5 16/16] fs/resctrl: Add documentation on kernel_mode with example Message-ID: References: Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: SJ0PR03CA0166.namprd03.prod.outlook.com (2603:10b6:a03:338::21) To SJ1PR11MB6083.namprd11.prod.outlook.com (2603:10b6:a03:48a::9) 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: SJ1PR11MB6083:EE_|MW5PR11MB5883:EE_ X-MS-Office365-Filtering-Correlation-Id: ab03c6f8-4833-4a0f-509f-08df086df3ad X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|23010399003|7416014|376014|10067099003|22082099003|18002099003|56012099006|4143699003|11063799006; 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Tried out several of the examples in the documentation and the ones I tried all worked. > +c. Narrow the association to CPUs 0-3 > +:: > + > + # echo 0-3 > /sys/fs/resctrl/ctrl1/kmode_cpus_list > + # cat /sys/fs/resctrl/ctrl1/kmode_cpus > + f > + # cat /sys/fs/resctrl/ctrl1/kmode_cpus_list > + 0-3 > + > +The write reprograms the association: > + > +- CPUs added to the mask are enabled. > +- CPUs removed from the mask are disabled. More precise to say: PLZA is enabled on CPUs added to the mask. PLZA is disabled on CPUs removed from the mask. Or perhaps PLZA reverts to "inherit_user" mode on CPUs removed from the mask. > +- Offline CPUs in the mask are rejected. > +- An empty mask disables the association on all currently online CPUs, but > + later hotplug CPUs are still associated automatically. Is there a use case for only enabling PLZA on some subset of CPUs? The special case for: # echo "" > ctrl1/kmode_cpus seems particularly strange. It reads to me as: "I want this PLZA feature enabled, but don't use it on any CPUs". -Tony