linux-kernel - Re: [PATCH v4 1/2] sched: Add per_cpu cluster domain info and cpus_share

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Message-ID: <47e3aafa-aae6-051d-99ec-528f7b609b38@huawei.com>
Date:   Fri, 10 Jun 2022 14:54:10 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Yicong Yang <yangyicong@...ilicon.com>, <peterz@...radead.org>,
        <mingo@...hat.com>, <juri.lelli@...hat.com>,
        <vincent.guittot@...aro.org>, <gautham.shenoy@....com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <dietmar.eggemann@....com>, <rostedt@...dmis.org>,
        <bsegall@...gle.com>, <bristot@...hat.com>,
        <prime.zeng@...wei.com>, <jonathan.cameron@...wei.com>,
        <ego@...ux.vnet.ibm.com>, <srikar@...ux.vnet.ibm.com>,
        <linuxarm@...wei.com>, <21cnbao@...il.com>,
        <guodong.xu@...aro.org>, <hesham.almatary@...wei.com>,
        <john.garry@...wei.com>, <shenyang39@...wei.com>
Subject: Re: [PATCH v4 1/2] sched: Add per_cpu cluster domain info and
 cpus_share_resources API

On 2022/6/10 6:28, Tim Chen wrote:
> On Thu, 2022-06-09 at 20:06 +0800, Yicong Yang wrote:
>>
>>  
>> +/*
>> + * Whether CPUs are share cache resources, which means LLC on non-cluster
>> + * machines and LLC tag or L2 on machines with clusters.
>> + */
>> +bool cpus_share_resources(int this_cpu, int that_cpu)
> 
> Suggest cpus_share_lowest_cache to be a bit more informative
> 
>> +{
>> +	if (this_cpu == that_cpu)
>> +		return true;
>> +
>> +	return per_cpu(sd_share_id, this_cpu) == per_cpu(sd_share_id, that_cpu);
>> +}
>> +
>>  static inline bool ttwu_queue_cond(int cpu, int wake_flags)
>>  {
>>  	/*
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index 01259611beb9..b9bcfcf8d14d 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -1753,7 +1753,9 @@ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
>>  DECLARE_PER_CPU(struct sched_domain __rcu *, sd_llc);
>>  DECLARE_PER_CPU(int, sd_llc_size);
>>  DECLARE_PER_CPU(int, sd_llc_id);
>> +DECLARE_PER_CPU(int, sd_share_id);
>>  DECLARE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
>> +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_cluster);
>>  DECLARE_PER_CPU(struct sched_domain __rcu *, sd_numa);
>>  DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
>>  DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
>> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
>> index 05b6c2ad90b9..0595827d481d 100644
>> --- a/kernel/sched/topology.c
>> +++ b/kernel/sched/topology.c
>> @@ -664,6 +664,8 @@ static void destroy_sched_domains(struct sched_domain *sd)
>>  DEFINE_PER_CPU(struct sched_domain __rcu *, sd_llc);
>>  DEFINE_PER_CPU(int, sd_llc_size);
>>  DEFINE_PER_CPU(int, sd_llc_id);
>> +DEFINE_PER_CPU(int, sd_share_id);
> 
> Some minor nits about the name of "sd_share_id".  
> It is not quite obvious what it is.  
> 
> Maybe something like sd_lowest_cache_id to denote
> it is the id of lowest shared cache domain between CPU. 
> 

Thanks for the suggestion! Since Vincent and Gautham have suggested this in v1 [1], I'd like
to wait a bit before changing to this to see if they have any comment.

> Otherwise the patch looks good to me.  You can add
> 
> Reviewed-by: Tim Chen <tim.c.chen@...ux.intel.com>
> 

Thanks.

[1] https://lore.kernel.org/lkml/CAKfTPtBKLDyNPXg7uLbQ3jUnEwppfC+E29=oJ1tWzzqHsNpApw@mail.gmail.com/