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    SubjectRe: [PATCH 03/11] mm: mmzone: introduce zone_pfn_same_memmap()
    Date
    From
    > On Fri, Nov 18, 2011 at 05:43:10PM +0100, Marek Szyprowski wrote:
    >> From: Michal Nazarewicz <mina86@mina86.com>
    >> diff --git a/mm/compaction.c b/mm/compaction.c
    >> index 6afae0e..09c9702 100644
    >> --- a/mm/compaction.c
    >> +++ b/mm/compaction.c
    >> @@ -111,7 +111,10 @@ skip:
    >>
    >> next:
    >> pfn += isolated;
    >> - page += isolated;
    >> + if (zone_pfn_same_memmap(pfn - isolated, pfn))
    >> + page += isolated;
    >> + else
    >> + page = pfn_to_page(pfn);
    >> }

    On Mon, 12 Dec 2011 15:19:53 +0100, Mel Gorman <mel@csn.ul.ie> wrote:
    > Is this necessary?
    >
    > We are isolating pages, the largest of which is a MAX_ORDER_NR_PAGES
    > page. [...]

    This is not true for CMA.

    > That said, everywhere else managed to avoid checks like this by always
    > scanning in units of pageblocks. Maybe this should be structured
    > the same way to guarantee pfn_valid is called at least per pageblock
    > (even though only once per MAX_ORDER_NR_PAGES is necessary).

    I'll look into that.

    --
    Best regards, _ _
    .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
    ..o | Computer Science, Michał “mina86” Nazarewicz (o o)
    ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo--
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