linux-kernel - Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable

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Message-ID: <d3a88afd-63c6-1091-cf4c-75cd10b7f547@arm.com>
Date:   Thu, 3 Oct 2019 17:02:11 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Qian Cai <cai@....pw>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Pavel Tatashin <pavel.tatashin@...rosoft.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in
 has_unmovable_pages()



On 10/03/2019 04:49 PM, Qian Cai wrote:
> 
> 
>> On Oct 3, 2019, at 5:32 AM, Anshuman Khandual <Anshuman.Khandual@....com> wrote:
>>
>> Even though page flags does contain reserved bit information, the problem
>> is that we are explicitly printing the reason for this page dump. In this
>> case it is caused by the fact that it is a reserved page.
>>
>> page dumped because: <reason>
>>
>> The proposed change makes it explicit that the dump is caused because a
>> non movable page with reserved bit set. It also helps in differentiating 
>> between reserved bit condition and the last one "if (found > count)".
> 
> Then, someone later would like to add a reason for every different page flags just because they *think* they are special.
> 

Ohh, never meant that the 'Reserved' bit is anything special here but it
is a reason to make a page unmovable unlike many other flags.