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

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Message-ID: <ec3e1d37-1b96-4a28-a5d8-cc92f3103085@gmail.com>
Date: Wed, 7 Feb 2024 10:36:59 +0800
From: kuiliang Shi <seakeel@...il.com>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.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 2/7/24 5:24 AM, Ricardo Neri wrote:
> 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.
> 

Thanks for comments. will update in next version.
>