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

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Message-Id: <7FA7CBE1-E0A9-40E2-B3CA-0896F6D491E5@lca.pw>
Date:   Thu, 3 Oct 2019 05:05:50 -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 4:10 AM, Anshuman Khandual <Anshuman.Khandual@....com> wrote:
> 
> Having unmovable pages on a given pageblock should be reported correctly
> when required with REPORT_FAILURE flag. But there can be a scenario where a
> reserved page in the page block will get reported as a generic "unmovable"
> reason code. Instead this should be changed to a more appropriate reason
> code like "Reserved page".

Isn’t this redundant as it dumps the flags in dump_page() anyway?

> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Pavel Tatashin <pavel.tatashin@...rosoft.com>
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> mm/page_alloc.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 15c2050c629b..fbf93ea119d2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8206,8 +8206,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
> 
>        page = pfn_to_page(check);
> 
> -        if (PageReserved(page))
> +        if (PageReserved(page)) {
> +            reason = "Reserved page";
>            goto unmovable;
> +        }
> 
>        /*
>         * If the zone is movable and we have ruled out all reserved
> -- 
> 2.20.1
>