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

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Date:   Tue, 11 Apr 2023 16:27:50 +0530
From:   K Prateek Nayak <kprateek.nayak@....com>
To:     Bagas Sanjaya <bagasdotme@...il.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

Hello Bagas,

On 4/11/2023 9:28 AM, Bagas Sanjaya wrote:
> 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>

Thank you for reviewing the patch :)

--
Thanks and Regards,
Prateek