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Subject: Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in
 has_unmovable_pages()
To:     Qian Cai <cai@lca.pw>
Cc:     linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Oscar Salvador <osalvador@suse.de>,
        Mel Gorman <mgorman@techsingularity.net>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Pavel Tatashin <pavel.tatashin@microsoft.com>,
        linux-kernel@vger.kernel.org
References: <37b43978-5652-576c-8990-451e751b7c67@arm.com>
 <285C0297-BF27-4095-87B6-AFC88C1F3C0F@lca.pw>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <d3a88afd-63c6-1091-cf4c-75cd10b7f547@arm.com>
Date:   Thu, 3 Oct 2019 17:02:11 +0530
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On 10/03/2019 04:49 PM, Qian Cai wrote:
> 
> 
>> On Oct 3, 2019, at 5:32 AM, Anshuman Khandual <Anshuman.Khandual@arm.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.