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Wysocki" , Huang Rui CC: , , , , Shuah Khan , , "Nathan Fontenot" , Deepak Sharma , Alex Deucher , Mario Limonciello , Shimmer Huang , "Perry Yuan" , Xiaojian Du , Viresh Kumar , Borislav Petkov , Meng Li Subject: [PATCH V4 6/7] Documentation: amd-pstate: introduce AMD Pstate Preferred Core Date: Tue, 29 Aug 2023 14:43:39 +0800 Message-ID: <20230829064340.1136448-7-li.meng@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230829064340.1136448-1-li.meng@amd.com> References: <20230829064340.1136448-1-li.meng@amd.com> MIME-Version: 1.0 X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF000044F2:EE_|IA1PR12MB6331:EE_ X-MS-Office365-Filtering-Correlation-Id: da167f23-97c8-4002-1e91-08dba85b7105 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230031)(4636009)(136003)(376002)(396003)(346002)(39860400002)(451199024)(1800799009)(186009)(82310400011)(36840700001)(40470700004)(46966006)(356005)(81166007)(82740400003)(8936002)(6666004)(110136005)(70206006)(70586007)(478600001)(7696005)(54906003)(6636002)(316002)(41300700001)(40460700003)(36756003)(26005)(16526019)(8676002)(1076003)(5660300002)(83380400001)(2906002)(2616005)(86362001)(47076005)(36860700001)(40480700001)(426003)(336012)(4326008)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Aug 2023 06:44:49.2989 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: da167f23-97c8-4002-1e91-08dba85b7105 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF000044F2.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6331 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Introduce AMD Pstate Preferred Core. check preferred core state: $ cat /sys/devices/system/cpu/amd-pstate/prefcore Signed-off-by: Meng Li --- Documentation/admin-guide/pm/amd-pstate.rst | 54 +++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index 1cf40f69278c..400264d52007 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -353,6 +353,48 @@ is activated. In this mode, driver requests minimum and maximum performance level and the platform autonomously selects a performance level in this range and appropriate to the current workload. +AMD Pstate Preferred Core +================================= + +The core frequency is subjected to the process variation in semiconductors. +Not all cores are able to reach the maximum frequency respecting the +infrastructure limits. Consequently, AMD has redefined the concept of +maximum frequency of a part. This means that a fraction of cores can reach +maximum frequency. To find the best process scheduling policy for a given +scenario, OS needs to know the core ordering informed by the platform through +highest performance capability register of the CPPC interface. + +``AMD Pstate Preferred Core`` enables the scheduler to prefer scheduling on +cores that can achieve a higher frequency with lower voltage. The preferred +core rankings can dynamically change based on the workload, platform conditions, +thermals and ageing. + +The priority metric will be initialized by the AMD Pstate driver. The AMD Pstate +driver will also determine whether or not ``AMD Pstate Preferred Core`` is +supported by the platform. + +AMD Pstate driver will provide an initial core ordering when the system boots. +The platform uses the CPPC interfaces to communicate the core ranking to the +operating system and scheduler to make sure that OS is choosing the cores +with highest performance firstly for scheduling the process. When AMD Pstate +driver receives a message with the highest performance change, it will +update the core ranking and set the cpu's priority. + +AMD Preferred Core Switch +================================= +Kernel Parameters +----------------- + +``AMD Pstate Preferred Core`` has two states: enable and disable. +Enable/disable states can be chosen by different kernel parameters. +Default enable ``AMD Pstate Preferred Core``. + +``amd_prefcore=disable`` + +for systems that support ``AMD Pstate Preferred Core``, the core rankings will +always be advertised by the platform. But OS can choose to ignore that via the +kernel parameter ``amd_prefcore=disable``. + User Space Interface in ``sysfs`` - General =========================================== @@ -385,6 +427,18 @@ control its functionality at the system level. They are located in the to the operation mode represented by that string - or to be unregistered in the "disable" case. +``prefcore`` + Preferred Core state of the driver: "enabled" or "disabled". + + "enabled" + Enable the AMD Preferred Core. + + "disabled" + Disable the AMD Preferred Core + + + This attribute is read-only to check the state of Preferred Core. + ``cpupower`` tool support for ``amd-pstate`` ===============================================