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

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Message-Id: <983E7EA4-A022-448C-B11D-8C10441A2E07@lca.pw>
Date:   Thu, 3 Oct 2019 07:50:31 -0400
From:   Qian Cai <cai@....pw>
To:     Anshuman Khandual <Anshuman.Khandual@....com>
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 Oct 3, 2019, at 7:31 AM, Anshuman Khandual <Anshuman.Khandual@....com> wrote:
> 
> 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.

But dump_page() is used everywhere, and it is better to reserve “reason” to indicate something more important rather than duplicating the page flags.

Especially, it is trivial enough right now for developers look in the page flags dumping from has_unmovable_pages(), and figure out the exact branching in the code.