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    Subject[PATCH 1/5 Against 2.6.31.4] page allocator: Always wake kswapd when restarting an allocation attempt after direct reclaim failed
    This is a version that applies against 2.6.31.4

    ==== CUT HERE ====
    page allocator: Always wake kswapd when restarting an allocation attempt after direct reclaim failed

    If a direct reclaim makes no forward progress, it considers whether it
    should go OOM or not. Whether OOM is triggered or not, it may retry the
    application afterwards. In times past, this would always wake kswapd as well
    but currently, kswapd is not woken up after direct reclaim fails. For order-0
    allocations, this makes little difference but if there is a heavy mix of
    higher-order allocations that direct reclaim is failing for, it might mean
    that kswapd is not rewoken for higher orders as much as it did previously.

    This patch wakes up kswapd when an allocation is being retried after a direct
    reclaim failure. It would be expected that kswapd is already awake, but
    this has the effect of telling kswapd to reclaim at the higher order as well.

    Signed-off-by: Mel Gorman <mel@csn.ul.ie>
    ---
    mm/page_alloc.c | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    index 0b3c6cb..239677a 100644
    --- a/mm/page_alloc.c
    +++ b/mm/page_alloc.c
    @@ -1763,6 +1763,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
    if (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
    goto nopage;

    +restart:
    wake_all_kswapd(order, zonelist, high_zoneidx);

    /*
    @@ -1772,7 +1773,6 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
    */
    alloc_flags = gfp_to_alloc_flags(gfp_mask);

    -restart:
    /* This is the last chance, in general, before the goto nopage. */
    page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist,
    high_zoneidx, alloc_flags & ~ALLOC_NO_WATERMARKS,
    --
    1.6.3.3


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