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

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Date: Sun, 4 Feb 2024 19:57:19 +0800
From: kuiliang Shi <seakeel@...il.com>
To: 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, ricardo.neri-calderon@...ux.intel.com,
 sshegde@...ux.ibm.com
Subject: Re: [PATCH v3 1/4] sched/fair: add SD_CLUSTER in comments



On 2/2/24 10:27 PM, 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 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

Double "shared", so could we use:
* SD_CLUSTER             - describes 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...

Uh, naming is a hard things. :)

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