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

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Date: Tue, 6 Feb 2024 13:24:18 -0800
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: kuiliang Shi <seakeel@...il.com>
Cc: Valentin Schneider <vschneid@...hat.com>, 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, sshegde@...ux.ibm.com
Subject: Re: [PATCH v3 1/4] sched/fair: add SD_CLUSTER in comments

On Tue, Feb 06, 2024 at 04:56:02PM +0800, kuiliang Shi wrote:
> 
> 
> On 2/6/24 10:46 AM, Ricardo Neri wrote:
> > On Fri, Feb 02, 2024 at 03:27:32PM +0100, Valentin Schneider wrote:
> >>
> >> 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 also thought of this, but I didn't want to suggest to repeat in topolog.c
> > what is described in sd_flags.h.
> > 
> > Maybe it is better to remove the descriptions of all flags here and instead
> > direct the reader to sd_flags.h?
> 
> yes, good idea for getting their meaning directly from the header file. 
> So is it fine for next sending?

Some tweaks below.

> 
>     sched/fair: remove duplicate comments for SD_ flags

      sched/topology: Remove duplicate descriptions from TOPOLOGY_SD_FLAGS
>     
>     Originally, it missed SD_CLUSTER flag description, but comparing to copy
>     the flags meaning from sd_flags.h, reader is better to get info from
>     there.

      These flags are already documented in include/linux/sched/sd_flags.h.

      Keep the comment on SD_ASYM_PACKING as it is a special case.
>     
>     Keep SD_ASYM_PACKING unchange for a point from another way.
>     
>     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>
> 
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 10d1391e7416..96a24bf954ad 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1551,11 +1551,7 @@ static struct cpumask            ***sched_domains_numa_masks;
>   *
>   * These flags are purely descriptive of the topology and do not prescribe
>   * behaviour. Behaviour is artificial and mapped in the below sd_init()
> - * function:
> - *
> - *   SD_SHARE_CPUCAPACITY   - describes SMT topologies
> - *   SD_SHARE_PKG_RESOURCES - describes shared caches
> - *   SD_NUMA                - describes NUMA topologies

Maybe only remove the descriptions but keep the enumeration?

> + * function, for details in include/linux/sched/sd_flags.h:

      function. For details, see include/linux/sched/sd_flags.h.