linux-kernel - Re: [PATCH v2 3/3] docs: cgroup-v1: clarify that domain levels are system-specific

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Date: Mon, 1 Apr 2024 09:35:44 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Vitalii Bursov <vitaly@...sov.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira
 <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] docs: cgroup-v1: clarify that domain levels are
 system-specific



On 3/31/24 9:31 PM, Vitalii Bursov wrote:
> Add a clarification that domain levels are system-specific
> and where to check for system details.
> 
> Add CPU clusters to the scheduler domain levels table.
> 
> Signed-off-by: Vitalii Bursov <vitaly@...sov.com>
> ---
>  Documentation/admin-guide/cgroup-v1/cpusets.rst | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/admin-guide/cgroup-v1/cpusets.rst b/Documentation/admin-guide/cgroup-v1/cpusets.rst
> index 7d3415eea..d16a3967d 100644
> --- a/Documentation/admin-guide/cgroup-v1/cpusets.rst
> +++ b/Documentation/admin-guide/cgroup-v1/cpusets.rst
> @@ -568,19 +568,25 @@ on the next tick.  For some applications in special situation, waiting
>  
>  The 'cpuset.sched_relax_domain_level' file allows you to request changing
>  this searching range as you like.  This file takes int value which
> -indicates size of searching range in levels ideally as follows,
> +indicates size of searching range in levels approximately as follows,
>  otherwise initial value -1 that indicates the cpuset has no request.
>  
>  ====== ===========================================================
>    -1   no request. use system default or follow request of others.
>     0   no search.
>     1   search siblings (hyperthreads in a core).
> -   2   search cores in a package.
> -   3   search cpus in a node [= system wide on non-NUMA system]
> -   4   search nodes in a chunk of node [on NUMA system]
> -   5   search system wide [on NUMA system]
> +   2   search cpu clusters
> +   3   search cores in a package.
> +   4   search cpus in a node [= system wide on non-NUMA system]
> +   5   search nodes in a chunk of node [on NUMA system]
> +   6   search system wide [on NUMA system]

I think above block of documentation need not change. SD_CLUSTER is a software 
construct, not a sched domain per se. 

IMO the next paragraph that is added is good enough and the above change can be removed.

>  ====== ===========================================================
>  
> +Not all levels can be present and values can change depending on the
> +system architecture and kernel configuration. Check
> +/sys/kernel/debug/sched/domains/cpu*/domain*/ for system-specific
> +details.
> +
>  The system default is architecture dependent.  The system default
>  can be changed using the relax_domain_level= boot parameter.
>