linux-kernel - Re: [PATCH v4 03/10] sched/topology: Provide cfs_overload

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Message-ID: <42abaaa5-6e3e-7362-7622-565f98e9629f@arm.com>
Date:   Sat, 8 Dec 2018 18:33:19 +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 v4 03/10] sched/topology: Provide cfs_overload_cpus bitmap

On 07/12/2018 22:35, Steven Sistare wrote:
[...]
>>> +	if (!sds->cfs_overload_cpus) {
>>> +		mask = sparsemask_alloc_node(nr_cpu_ids, 3, flags, nid);
>>                                              ^^^^^^^^^^ ^^^
>>                                                  (1)    (2)
>>
>> (1): Is this necessary? Wouldn't cpumask_weight(span) suffice?
> 
> weight does not work because the ids are not consecutive.  As a future 
> optimization I have a patch that computes a local CPU id within the LLC
> and uses that as the bitmap index, and that uses weight.  For this first
> series I am keeping things simple.
> 

Oh, duh, non-contiguous spans strike again. Fair enough!

[...]