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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Apr 2023 03:18:02.2347 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 53753226-852a-42c4-8af8-08db3c96db2a 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: BN8NAM11FT010.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ1PR12MB6361 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org x86 processors map cluster to the L2 cache. Add documentation stating the same, and provide more information on the values and API related to CPU clusters exposed by the kernel. Suggested-by: Dave Hansen # cluster_id description Signed-off-by: K Prateek Nayak --- o v2->v2.1 - Reword the cluster_id description based on Dave's suggestions. o v1->v2 - Reworded the definition of cluster on x86 based on Peter's suggestion. - Fixed double spacing before and after the cluster section. --- Documentation/x86/topology.rst | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/Documentation/x86/topology.rst b/Documentation/x86/topology.rst index 7f58010ea86a..9de14f3f7783 100644 --- a/Documentation/x86/topology.rst +++ b/Documentation/x86/topology.rst @@ -33,6 +33,7 @@ historical nature and should be cleaned up. The topology of a system is described in the units of: - packages + - cluster - cores - threads @@ -90,6 +91,22 @@ Package-related topology information in the kernel: Cache. In general, it is a number identifying an LLC uniquely on the system. +Clusters +======== +A cluster consists of threads of one or more cores sharing the same L2 cache. + +Cluster-related topology information in the kernel: + + - cluster_id: + + A per-CPU variable containing: + + - Upper bits extracted from the APIC ID. CPUs which have the same value + in these bits share an L2 and have the same cluster_id. + + CPUs for which cluster information is unavailable will show 65535 + (BAD_APICID) as the cluster_id. + Cores ===== A core consists of 1 or more threads. It does not matter whether the threads @@ -125,6 +142,11 @@ Thread-related topology information in the kernel: The number of online threads is also printed in /proc/cpuinfo "siblings." + - topology_cluster_cpumask(): + + The cpumask contains all online threads in the cluster to which a thread + belongs. + - topology_sibling_cpumask(): The cpumask contains all online threads in the core to which a thread @@ -138,6 +160,10 @@ Thread-related topology information in the kernel: The physical package ID to which a thread belongs. + - topology_cluster_id(); + + The ID of the cluster to which a thread belongs. + - topology_core_id(); The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo -- 2.34.1