linux-kernel - Re: [PATCH v2 2/3] mm/memory_hotplug: document why shuffle

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Message-ID: <d8b744d8-ad42-cdbc-f136-2798d68dd049@redhat.com>
Date:   Wed, 24 Jun 2020 11:31:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v2 2/3] mm/memory_hotplug: document why shuffle_zone() is
 relevant

On 23.06.20 23:15, Dan Williams wrote:
> On Mon, Jun 22, 2020 at 12:28 AM David Hildenbrand <david@...hat.com> wrote:
>>
>> On 20.06.20 03:41, Dan Williams wrote:
>>> On Fri, Jun 19, 2020 at 6:00 AM David Hildenbrand <david@...hat.com> wrote:
>>>>
>>>> It's not completely obvious why we have to shuffle the complete zone, as
>>>> some sort of shuffling is already performed when onlining pages via
>>>> __free_one_page(), placing MAX_ORDER-1 pages either to the head or the tail
>>>> of the freelist. Let's document why we have to shuffle the complete zone
>>>> when exposing larger, contiguous physical memory areas to the buddy.
>>>>
>>>
>>> How about?
>>>
>>> Fixes: e900a918b098 ("mm: shuffle initial free memory to improve
>>> memory-side-cache utilization")
>>>
>>> ...just like Patch1 since that original commit was missing the proper
>>> commentary in the code?
>>
>> Hmm, mixed feelings. I (working for a distributor :) ) prefer fixes tags
>> for actual BUGs, as described in
>>
>> Documentation/process/submitting-patches.rst: "If your patch fixes a bug
>> in a specific commit, e.g. you found an issue using ``git bisect``,
>> please use the 'Fixes:' tag with the first 12 characters" ...
>>
>> So unless there are strong feelings, I'll not add a fixes tag (although
>> I agree, that it should have been contained in the original commit).
> 
> It doesn't need to be "Fixes", but how about at least mentioning the
> original commit as a breadcrumb so that some future "git blame"
> archaeology effort is streamlined.
> 

Makes sense, I'll mention it as

It's not completely obvious why we have to shuffle the complete zone (
introduced in commit e900a918b098 ("mm: shuffle initial free memory to
...

thanks!

-- 
Thanks,

David / dhildenb