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

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Message-ID: <20130204234358.GB2610@blaptop>
Date:	Tue, 5 Feb 2013 08:43:58 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Kyungmin Park <kmpark@...radead.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

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?

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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