linux-kernel - Re: [PATCH v3 03/10] sched/topology: Provide cfs_overload

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Date:   Tue, 20 Nov 2018 12:52:18 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Steven Sistare <steven.sistare@...cle.com>, mingo@...hat.com,
        peterz@...radead.org
Cc:     subhra.mazumdar@...cle.com, dhaval.giani@...cle.com,
        daniel.m.jordan@...cle.com, pavel.tatashin@...rosoft.com,
        matt@...eblueprint.co.uk, umgwanakikbuti@...il.com,
        riel@...hat.com, jbacik@...com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, quentin.perret@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 03/10] sched/topology: Provide cfs_overload_cpus bitmap



On 19/11/2018 17:32, Steven Sistare wrote:
> On 11/9/2018 12:38 PM, Valentin Schneider wrote:
>> Hi Steve,
>>
>> On 09/11/2018 12:50, Steve Sistare wrote:
>> [...]
>>> @@ -482,6 +484,10 @@ static void update_top_cache_domain(int cpu)
>>>  	dirty_sched_domain_sysctl(cpu);
>>>  	destroy_sched_domains(tmp);
>>>  
>>> +	sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
>>> +	cfs_overload_cpus = (sd ? sd->shared->cfs_overload_cpus : NULL);
>>> +	rcu_assign_pointer(rq->cfs_overload_cpus, cfs_overload_cpus);
>>> +
>>
>> Why not do this in update_top_cache_domain() where we also look for the
>> highest SD_SHARE_PKG_RESOURCES and setup shortcut pointers?
> 
> My snippet needs rq which is currently referenced in cpu_attach_domain() but
> not in update_top_cache_domain().  I could just as easily do it in 
> update_top_cache_domain().  Either way is fine with me.
> 

I think having this in update_top_cache_domain() makes more sense - it's
where all the domain shortcuts are set, and we already play with LLC there.

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