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    SubjectRe: [PATCH 09/11] mm: vmscan: When reclaiming for compaction, ensure there are sufficient free pages available
    On 12/14/2011 10:41 AM, Mel Gorman wrote:
    > In commit [e0887c19: vmscan: limit direct reclaim for higher order
    > allocations], Rik noted that reclaim was too aggressive when THP was
    > enabled. In his initial patch he used the number of free pages to
    > decide if reclaim should abort for compaction. My feedback was that
    > reclaim and compaction should be using the same logic when deciding if
    > reclaim should be aborted.
    > Unfortunately, this had the effect of reducing THP success rates when
    > the workload included something like streaming reads that continually
    > allocated pages. The window during which compaction could run and return
    > a THP was too small.
    > This patch combines Rik's two patches together. compaction_suitable()
    > is still used to decide if reclaim should be aborted to allow
    > compaction is used. However, it will also ensure that there is a
    > reasonable buffer of free pages available. This improves upon the
    > THP allocation success rates but bounds the number of pages that are
    > freed for compaction.
    > Signed-off-by: Mel Gorman<>

    Reviewed-by: Rik van Riel<>

    All rights reversed

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