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    SubjectRe: [PATCH 0/4] big chunk memory allocator v4
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    On Fri, Nov 19, 2010 at 10:56 PM, Andrew Morton
    <akpm@linux-foundation.org> wrote:
    > On Fri, 19 Nov 2010 17:10:33 +0900
    > KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
    >
    >> Hi, this is an updated version.
    >>
    >> No major changes from the last one except for page allocation function.
    >> removed RFC.
    >>
    >> Order of patches is
    >>
    >> [1/4] move some functions from memory_hotplug.c to page_isolation.c
    >> [2/4] search physically contiguous range suitable for big chunk alloc.
    >> [3/4] allocate big chunk memory based on memory hotplug(migration) technique
    >> [4/4] modify page allocation function.
    >>
    >> For what:
    >>
    >>   I hear there is requirements to allocate a chunk of page which is larger than
    >>   MAX_ORDER. Now, some (embeded) device use a big memory chunk. To use memory,
    >>   they hide some memory range by boot option (mem=) and use hidden memory
    >>   for its own purpose. But this seems a lack of feature in memory management.

    Actually, now that's not needed any more by using memblock:
    http://article.gmane.org/gmane.linux.ports.arm.omap/44978

    >>   This patch adds
    >>       alloc_contig_pages(start, end, nr_pages, gfp_mask)
    >>   to allocate a chunk of page whose length is nr_pages from [start, end)
    >>   phys address. This uses similar logic of memory-unplug, which tries to
    >>   offline [start, end) pages. By this, drivers can allocate 30M or 128M or
    >>   much bigger memory chunk on demand. (I allocated 1G chunk in my test).
    >>
    >>   But yes, because of fragmentation, this cannot guarantee 100% alloc.
    >>   If alloc_contig_pages() is called in system boot up or movable_zone is used,
    >>   this allocation succeeds at high rate.
    >
    > So this is an alternatve implementation for the functionality offered
    > by Michal's "The Contiguous Memory Allocator framework".
    >
    >>   I tested this on x86-64, and it seems to work as expected. But feedback from
    >>   embeded guys are appreciated because I think they are main user of this
    >>   function.
    >
    > From where I sit, feedback from the embedded guys is *vital*, because
    > they are indeed the main users.
    >
    > Michal, I haven't made a note of all the people who are interested in
    > and who are potential users of this code.  Your patch series has a
    > billion cc's and is up to version 6.  Could I ask that you review and
    > test this code, and also hunt down other people (probably at other
    > organisations) who can do likewise for us?  Because until we hear from
    > those people that this work satisfies their needs, we can't really
    > proceed much further.

    As I've explained before, a contiguous memory allocator would be nice,
    but on ARM many drivers not only need contiguous memory, but
    non-cacheable, and this requires removing the memory from normal
    kernel mapping in early boot.

    Cheers.

    --
    Felipe Contreras
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