linux-kernel - Re: [PATCH] mm: cma: fix accounting of CMA pages placed in high memory

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Message-ID: <CAH9JG2VDOVv4-QrDs1FeyQNPzEDq+bf+qiSZ0snEqLGSed3PqA@mail.gmail.com>
Date:	Tue, 5 Feb 2013 08:52:02 +0900
From:	Kyungmin Park <kmpark@...radead.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, mgorman@...e.de
Subject: Re: [PATCH] mm: cma: fix accounting of CMA pages placed in high memory

Hi,

On Tue, Feb 5, 2013 at 8:43 AM, Minchan Kim <minchan@...nel.org> wrote:
> Hello,
>
> On Tue, Feb 05, 2013 at 08:29:26AM +0900, Kyungmin Park wrote:
>> On Tue, Feb 5, 2013 at 8:06 AM, Andrew Morton <akpm@...ux-foundation.org> wrote:
>> > On Mon, 04 Feb 2013 11:27:05 +0100
>> > Marek Szyprowski <m.szyprowski@...sung.com> wrote:
>> >
>> >> The total number of low memory pages is determined as
>> >> totalram_pages - totalhigh_pages, so without this patch all CMA
>> >> pageblocks placed in highmem were accounted to low memory.
>> >
>> > What are the end-user-visible effects of this bug?
>>
>> Even though CMA is located at highmem. LowTotal has more than lowmem
>> address spaces.
>>
>> e.g.,
>> lowmem  : 0xc0000000 - 0xdf000000   ( 496 MB)
>> LowTotal:         555788 kB
>>
>> >
>> > (This information is needed so that others can make patch-scheduling
>> > decisions and should be included in all bugfix changelogs unless it is
>> > obvious).
>>
>> CMA Highmem support is new feature. so don't need to go stable tree.
>
> I would like to clarify it because I remembered alloc_migrate_target have considered
> CMA pages could be highmem. Is it really new feature? If so, could you point out
> enabling patches for the new feature?
>
Here's related patch.
http://www.spinics.net/lists/arm-kernel/msg222369.html

Previous time, it's not fully tested and now we checked it with
highmem support patches.

Thank you,
Kyungmin Park
> struct page *alloc_migrate_target(struct page *page, unsigned long private,
>                                   int **resultp)
> {
>         gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
>
>         if (PageHighMem(page))
>                 gfp_mask |= __GFP_HIGHMEM;
>
>         return alloc_page(gfp_mask);
> }
>


> Thanks.
>
>>
>> Thank you,
>> Kyungmin Park
>> >
>> > --
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>>
>> --
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>
> --
> Kind regards,
> Minchan Kim
>
> --
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