linux-kernel - Re: [PATCH v3 6/7] x86/smpboot: introduce per-cpu variable for HT siblings

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Message-ID: <fb445f4b-e415-d92b-4ca6-f104cb5fc9cb@oracle.com>
Date:   Thu, 27 Jun 2019 18:06:47 -0700
From:   Subhra Mazumdar <subhra.mazumdar@...cle.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, steven.sistare@...cle.com,
        dhaval.giani@...cle.com, daniel.lezcano@...aro.org,
        vincent.guittot@...aro.org, viresh.kumar@...aro.org,
        tim.c.chen@...ux.intel.com, mgorman@...hsingularity.net
Subject: Re: [PATCH v3 6/7] x86/smpboot: introduce per-cpu variable for HT
 siblings


On 6/26/19 11:54 PM, Thomas Gleixner wrote:
> On Thu, 27 Jun 2019, Thomas Gleixner wrote:
>
>> On Wed, 26 Jun 2019, subhra mazumdar wrote:
>>
>>> Introduce a per-cpu variable to keep the number of HT siblings of a cpu.
>>> This will be used for quick lookup in select_idle_cpu to determine the
>>> limits of search.
>> Why? The number of siblings is constant at least today unless you play
>> silly cpu hotplug games. A bit more justification for adding yet another
>> random storage would be appreciated.
>>
>>> This patch does it only for x86.
>> # grep 'This patch' Documentation/process/submitting-patches.rst
>>
>> IOW, we all know already that this is a patch and from the subject prefix
>> and the diffstat it's pretty obvious that this is x86 only.
>>
>> So instead of documenting the obvious, please add proper context to justify
>> the change.
> Aside of that the right ordering is to introduce the default fallback in a
> separate patch, which explains the reasoning and then in the next one add
> the x86 optimized version.
OK. I will also add the extra optimization for other architectures.

Thanks,
Subhra
>
> Thanks,
>
> 	tglx