linux-kernel - Re: [PATCH 2/2] x86/Documentation: Add documentation about cluster

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Date:   Tue, 11 Apr 2023 10:58:12 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     K Prateek Nayak <kprateek.nayak@....com>,
        linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, corbet@....net,
        jgross@...e.com, andrew.cooper3@...rix.com, peterz@...radead.org,
        Jason@...c4.com, thomas.lendacky@....com, puwen@...on.cn,
        x86@...nel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 2/2] x86/Documentation: Add documentation about cluster

On Mon, Apr 10, 2023 at 10:05:27PM +0530, K Prateek Nayak wrote:
> diff --git a/Documentation/x86/topology.rst b/Documentation/x86/topology.rst
> index 7f58010ea86a..35991d8cdef1 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 +91,27 @@ 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 1 or more threads. It does not matter whether the threads
> +are SMT- or CMT-type threads. All the threads of a cluster share the same L2
> +cache.
> +
> +Cluster-related topology information in the kernel:
> +
> +  - cluster_id:
> +
> +    A per-CPU variable containing:
> +
> +      - On Intel, the common upper bits of APIC ID of the list of CPUs sharing
> +        the L2 Cache with lower bits set to 0.
> +
> +      - On AMD, with Topology Extension, the common upper bits of the Extended
> +        APIC ID of the list of CPUs sharing the L2 Cache, left shifted to
> +        remove trailing 0s.
> +
> +
>  Cores
>  =====
>  A core consists of 1 or more threads. It does not matter whether the threads
> @@ -125,6 +147,11 @@ 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 +165,10 @@ 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

The doc LGTM, thanks!

Reviewed-by: Bagas Sanjaya <bagasdotme@...il.com>

-- 
An old man doll... just what I always wanted! - Clara

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