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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 V8 6/7] Documentation: amd-pstate: introduce amd-pstate preferred core Date: Mon, 9 Oct 2023 10:49:31 +0800 Message-ID: <20231009024932.2563622-7-li.meng@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231009024932.2563622-1-li.meng@amd.com> References: <20231009024932.2563622-1-li.meng@amd.com> MIME-Version: 1.0 X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF0001AB51:EE_|PH7PR12MB8828:EE_ X-MS-Office365-Filtering-Correlation-Id: 0c90555f-8308-4450-d7b9-08dbc8728e76 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)(39860400002)(376002)(396003)(346002)(230922051799003)(64100799003)(1800799009)(82310400011)(451199024)(186009)(46966006)(40470700004)(36840700001)(2616005)(1076003)(16526019)(426003)(336012)(26005)(54906003)(70586007)(70206006)(110136005)(6636002)(2906002)(83380400001)(40460700003)(86362001)(36756003)(47076005)(36860700001)(7696005)(6666004)(478600001)(5660300002)(8676002)(8936002)(4326008)(316002)(41300700001)(81166007)(40480700001)(356005)(82740400003)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Oct 2023 02:50:54.4724 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0c90555f-8308-4450-d7b9-08dbc8728e76 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: BL6PEPF0001AB51.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB8828 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Introduce amd-pstate preferred core. check preferred core state set by the kernel parameter: $ cat /sys/devices/system/cpu/amd-pstate/prefcore Reviewed-by: Mario Limonciello Reviewed-by: Huang Rui Signed-off-by: Meng Li Reviewed-by: Wyes Karny --- Documentation/admin-guide/pm/amd-pstate.rst | 59 ++++++++++++++++++++- 1 file changed, 57 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index 1cf40f69278c..0b832ff529db 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -300,8 +300,8 @@ platforms. The AMD P-States mechanism is the more performance and energy efficiency frequency management method on AMD processors. -AMD Pstate Driver Operation Modes -================================= +``amd-pstate`` Driver Operation Modes +====================================== ``amd_pstate`` CPPC has 3 operation modes: autonomous (active) mode, non-autonomous (passive) mode and guided autonomous (guided) mode. @@ -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-pstate`` Preferred Core Switch +================================= +Kernel Parameters +----------------- + +``amd-pstate`` peferred 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 +427,19 @@ 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-pstate`` preferred core. + + "disabled" + Disable the ``amd-pstate`` preferred core + + + This attribute is read-only to check the state of preferred core set + by the kernel parameter. + ``cpupower`` tool support for ``amd-pstate`` ===============================================