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    SubjectRe: [PATCH 2/9] mm: alloc_contig_freed_pages() added
    On Sun, Oct 23, 2011 at 09:05:05PM -0700, Michal Nazarewicz wrote:
    > > On Thu, Oct 06, 2011 at 03:54:42PM +0200, Marek Szyprowski wrote:
    > >> This commit introduces alloc_contig_freed_pages() function
    > >> which allocates (ie. removes from buddy system) free pages
    > >> in range. Caller has to guarantee that all pages in range
    > >> are in buddy system.
    > On Tue, 18 Oct 2011 05:21:09 -0700, Mel Gorman <> wrote:
    > > Straight away, I'm wondering why you didn't use
    > > mm/compaction.c#isolate_freepages()
    > Does the below look like a step in the right direction?
    > It basically moves isolate_freepages_block() to page_alloc.c (changing

    For the purposes of review, have a separate patch for moving
    isolate_freepages_block to another file that does not alter the
    function in any way. When the function is updated in a follow-on patch,
    it'll be far easier to see what has changed.

    page_isolation.c may also be a better fit than page_alloc.c

    As it is, the patch for isolate_freepages_block is almost impossible
    to read because it's getting munged with existing code that is already
    in page_alloc.c . About all I caught from it is that scannedp does
    not have a type. It defaults to unsigned int but it's unnecessarily

    > it name to isolate_freepages_range()) and changes it so that depending
    > on arguments it treats holes (either invalid PFN or non-free page) as
    > errors so that CMA can use it.

    I haven't actually read the function because it's too badly mixed with
    page_alloc.c code but this description fits what I'm looking for.

    > It also accepts a range rather then just assuming a single pageblock
    > thus the change moves range calculation in compaction.c from
    > isolate_freepages_block() up to isolate_freepages().
    > The change also modifies spilt_free_page() so that it does not try to
    > change pageblock's migrate type if current migrate type is ISOLATE or
    > CMA.

    This is fine. Later, the flags that determine what happens to pageblocks
    may be placed in compact_control.

    > ---
    > include/linux/mm.h | 1 -
    > include/linux/page-isolation.h | 4 +-
    > mm/compaction.c | 73 +++--------------------
    > mm/internal.h | 5 ++
    > mm/page_alloc.c | 128 +++++++++++++++++++++++++---------------
    > 5 files changed, 95 insertions(+), 116 deletions(-)

    I confess I didn't read closely because of the mess in page_alloc.c but
    the intent seems fine. Hopefully there will be a new version of CMA
    posted that will be easier to review.


    Mel Gorman
    SUSE Labs

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