linux-kernel - Re: [PATCH RFC 3/4] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype

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Date:   Fri, 18 Sep 2020 09:30:54 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Wei Yang <richard.weiyang@...ux.alibaba.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-hyperv@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-acpi@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Rapoport <rppt@...nel.org>,
        Scott Cheloha <cheloha@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH RFC 3/4] mm/page_alloc: always move pages to the tail of
 the freelist in unset_migratetype_isolate()

On 18.09.20 04:29, Wei Yang wrote:
> On Wed, Sep 16, 2020 at 08:34:10PM +0200, David Hildenbrand wrote:
>> Page isolation doesn't actually touch the pages, it simply isolates
>> pageblocks and moves all free pages to the MIGRATE_ISOLATE freelist.
>>
>> We already place pages to the tail of the freelists when undoing
>> isolation via __putback_isolated_page(), let's do it in any case
>> (e.g., if order == pageblock_order) and document the behavior.
>>
>> This change results in all pages getting onlined via online_pages() to
>> be placed to the tail of the freelist.
> 
> I am sorry to not follow again. unset_migratetype_isolate() is used in
> __offline_pages if my understanding is correct. How does it contribute on
> online_pages? 

See -next / -mm, that should make it clearer.

-- 
Thanks,

David / dhildenb