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    SubjectRe: [PATCH 0/2] Synchronous Lumpy Reclaim V3
    On Thu, 2007-08-02 at 19:17 +0100, Andy Whitcroft wrote:
    > [This is a re-spin based on feedback from akpm.]
    > As pointed out by Mel when reclaim is applied at higher orders a
    > significant amount of IO may be started. As this takes finite time
    > to drain reclaim will consider more areas than ultimatly needed
    > to satisfy the request. This leads to more reclaim than strictly
    > required and reduced success rates.
    > I was able to confirm Mel's test results on systems locally.
    > These show that even under light load the success rates drop off far
    > more than expected. Testing with a modified version of his patch
    > (which follows) I was able to allocate almost all of ZONE_MOVABLE
    > with a near idle system. I ran 5 test passes sequentially following
    > system boot (the system has 29 hugepages in ZONE_MOVABLE):
    > 2.6.23-rc1 11 8 6 7 7
    > sync_lumpy 28 28 29 29 26
    > These show that although hugely better than the near 0% success
    > normally expected we can only allocate about a 1/4 of the zone.
    > Using synchronous reclaim for these allocations we get close to 100%
    > as expected.
    > I have also run our standard high order tests and these show no
    > regressions in allocation success rates at rest, and some significant
    > improvements under load.
    > Following this email are two patches, both should be considered as
    > bug fixes to lumpy reclaim for 2.6.23:
    > ensure-we-count-pages-transitioning-inactive-via-clear_active_flags:
    > this a bug fix for Lumpy Reclaim fixing up a bug in VM Event
    > accounting when it marks pages inactive, and
    > Wait-for-page-writeback-when-directly-reclaiming-contiguous-areas:
    > updates reclaim making direct reclaim synchronous when applied
    > at orders above PAGE_ALLOC_COSTLY_ORDER.
    > Patches against 2.6.23-rc1. Andrew please consider for -mm and
    > for pushing to mainline.

    Acked-by: Peter Zijlstra <>

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