linux-kernel - Re: [PATCH v3 1/4] sched/fair: add SD

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Date: Fri, 02 Feb 2024 15:27:32 +0100
From: Valentin Schneider <vschneid@...hat.com>
To: alexs@...nel.org, 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>, Daniel Bristot de Oliveira
 <bristot@...hat.com>, linux-kernel@...r.kernel.org,
 ricardo.neri-calderon@...ux.intel.com, sshegde@...ux.ibm.com
Cc: Alex Shi <alexs@...nel.org>
Subject: Re: [PATCH v3 1/4] sched/fair: add SD_CLUSTER in comments


Subject nit: the prefix should be sched/topology

On 01/02/24 19:54, alexs@...nel.org wrote:
> From: Alex Shi <alexs@...nel.org>
>
> The description of SD_CLUSTER is missing. Add it.
>
> Signed-off-by: Alex Shi <alexs@...nel.org>
> To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> To: Valentin Schneider <vschneid@...hat.com>
> To: Vincent Guittot <vincent.guittot@...aro.org>
> To: Juri Lelli <juri.lelli@...hat.com>
> To: Peter Zijlstra <peterz@...radead.org>
> To: Ingo Molnar <mingo@...hat.com>
> ---
>  kernel/sched/topology.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 10d1391e7416..8b45f16a1890 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1554,6 +1554,7 @@ static struct cpumask		***sched_domains_numa_masks;
>   * function:
>   *
>   *   SD_SHARE_CPUCAPACITY   - describes SMT topologies
> + *   SD_CLUSTER             - describes CPU Cluster topologies

So I know this is the naming we've gone for the "Cluster" naming, but this
comment isn't really explaining anything.

include/linux/sched/sd_flags.h has a bit more info already:
 * Domain members share CPU cluster (LLC tags or L2 cache)

I had to go through a bit of git history to remember what the CLUSTER thing
was about, how about this:

* SD_CLUSTER             - describes shared shared caches, cache tags or busses
* SD_SHARE_PKG_RESOURCES - describes shared LLC cache

And looking at this it would make sense to:
  rename SD_CLUSTER into SD_SHARE_PKG_RESOURCES
  rename SD_SHARE_PKG_RESOURCES into SD_SHARE_LLC
but that's another topic...

>   *   SD_SHARE_PKG_RESOURCES - describes shared caches
>   *   SD_NUMA                - describes NUMA topologies
>   *
> --
> 2.43.0