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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 V6 6/7] Documentation: amd-pstate: introduce amd-pstate preferred core Date: Fri, 8 Sep 2023 15:46:52 +0800 Message-ID: <20230908074653.2799055-7-li.meng@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230908074653.2799055-1-li.meng@amd.com> References: <20230908074653.2799055-1-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: CO1PEPF000044FC:EE_|SJ0PR12MB6829:EE_ X-MS-Office365-Filtering-Correlation-Id: 59f5bd56-b4f6-4972-a604-08dbb03feead 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)(396003)(346002)(39860400002)(376002)(136003)(186009)(1800799009)(82310400011)(451199024)(40470700004)(46966006)(36840700001)(7696005)(40460700003)(41300700001)(316002)(81166007)(82740400003)(36756003)(2906002)(478600001)(86362001)(356005)(110136005)(70206006)(54906003)(70586007)(6636002)(6666004)(40480700001)(83380400001)(2616005)(5660300002)(1076003)(47076005)(8936002)(4326008)(8676002)(16526019)(26005)(426003)(336012)(36860700001)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2023 07:48:03.5436 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 59f5bd56-b4f6-4972-a604-08dbb03feead 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: CO1PEPF000044FC.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB6829 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 | 58 ++++++++++++++++++++- 1 file changed, 56 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index 1cf40f69278c..b729bc6dabd8 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 +427,18 @@ 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-pstate`` preferred core. + + "disabled" + Disable the ``amd-pstate`` preferred core + + + This attribute is read-only to check the state of preferred core. + ``cpupower`` tool support for ``amd-pstate`` ===============================================