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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 , "Oleksandr Natalenko" , Meng Li , Wyes Karny , Perry Yuan Subject: [PATCH V12 6/7] Documentation: amd-pstate: introduce amd-pstate preferred core Date: Tue, 5 Dec 2023 14:35:36 +0800 Message-ID: <20231205063537.872834-7-li.meng@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231205063537.872834-1-li.meng@amd.com> References: <20231205063537.872834-1-li.meng@amd.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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: DS3PEPF000099DB:EE_|LV3PR12MB9188:EE_ X-MS-Office365-Filtering-Correlation-Id: 9393f710-805d-4e63-45c6-08dbf55cd62a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: cFg2p5jH+GHpyNNroDt23A1+crrHhIDl3tLy3vrewCnkuQ4HBRJrSlPl3eYXLf/4MyDab0KN3h5nERv2EapXHU1MI5MCgcjk7nZGOrB4dTyADcFA3T9qmVjWssgI8aih8RDQ01LMEwjWmeLVuDu3nJCROX8H4mEq/u468yST8TXxeMxS1aDy3tisjXN2vNT+dSKrPaLZvNDDlbv9WfHjxCekPbwGCGTgXz1oBnDfHDXkW8M6RJdi9+4pdDpn/uJXTdpFWTbEiIm7vnnxVNfoI8xU9yww2awco5k7y1yRhqoAwlxkqUq4DM2aN9qu+grjELpptsM5pH9cfLAlbwltXL7+jC4jGHtTQ6f29m5myS6sUJxFrahghzzfhart7r/WPEtVWtsI/B3J2m9A5yDW7piVjYDNKjX/BBuHkA8WwNsEmJ5OM8GHl+nisp7XlOGWWMJ4oQbuyWoS0UZuTCyN7/rzBaoqwRTEtKSwoqddGx7uWRSC8Utvtw6YaYNW4s9HblJFF7rfbi0FhkZcsob41oP3cTqrhmuKjID7hhuTiJdG+Y9WS7RVnsAFMsuBW6czpjXi3nTFvgLXoBHu8FNfBIuEUwjG3Em388PseXeNA6YzcQ/gTCY5+rHWgf0s8lOJJD0WeOSf6DAovkoWXWdqhwWoLH4WIygV6VSgxPeMMPkmgEyR9nXuQZzmft6dCenCDmaJK7k3SJVznFG5wNQVu41msRZTILE5fyeOwdtDFq1dVYzPGRHkE4UfpMQtU45eDmeFocRR8JvjNMT//QqqkA== 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)(39860400002)(376002)(346002)(396003)(136003)(230922051799003)(186009)(64100799003)(82310400011)(1800799012)(451199024)(36840700001)(46966006)(40470700004)(7416002)(40480700001)(36860700001)(2906002)(110136005)(316002)(6636002)(54906003)(86362001)(70206006)(70586007)(36756003)(41300700001)(8676002)(8936002)(4326008)(356005)(47076005)(5660300002)(82740400003)(81166007)(83380400001)(478600001)(40460700003)(426003)(16526019)(336012)(26005)(1076003)(7696005)(6666004)(2616005)(36900700001); DIR:OUT; SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Dec 2023 06:38:48.0541 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9393f710-805d-4e63-45c6-08dbf55cd62a 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: DS3PEPF000099DB.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR12MB9188 Introduce amd-pstate preferred core. check preferred core state set by the kernel parameter: $ cat /sys/devices/system/cpu/amd-pstate/prefcore Tested-by: Oleksandr Natalenko Reviewed-by: Wyes Karny Reviewed-by: Mario Limonciello Reviewed-by: Huang Rui Reviewed-by: Perry Yuan Signed-off-by: Meng Li --- 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`` ===============================================