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    SubjectRe: [PATCH 1/2] mm: page allocator: Initialise ZLC for first zone eligible for zone_reclaim
    Hmmm... Maybe we can bypass the checks?

    Subject: [page allocator] Do not check watermarks if there is a page available on the per cpu freelists

    One should be able to grab a page from the per cpu freelists if available.
    The pages on the per cpu freelists are not accounted for in VM statistics
    so getting a page from there has no impact on reclaim.

    Check for this condition in get_page_from_freelist and short circuit
    to the call to buffered_rmqueue if so.

    Note that there is a race here. We may deplete the reserve pools by
    one page if either the process is rescheduled on a different processor
    or if another process grabs the last page from the per cpu freelist.

    Signed-off-by: Christoph Lameter <>

    mm/page_alloc.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    Index: linux-2.6/mm/page_alloc.c
    --- linux-2.6.orig/mm/page_alloc.c 2011-07-20 15:27:20.544825852 -0500
    +++ linux-2.6/mm/page_alloc.c 2011-07-20 15:30:05.314824797 -0500
    @@ -1666,6 +1666,16 @@ zonelist_scan:
    !cpuset_zone_allowed_softwall(zone, gfp_mask))
    goto try_next_zone;

    + /*
    + * Short circuit allocation if we have a usable object on
    + * the percpu freelist. Note that this can only be an
    + * optimization since there is no guarantee that we will
    + * be executing on the same cpu. Another process could also
    + * be scheduled and take the available page from us.
    + */
    + if (order == 0 && this_cpu_read(zone->pageset->pcp.count))
    + goto try_this_zone;
    if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
    unsigned long mark;

     \ /
      Last update: 2011-07-20 23:19    [W:0.023 / U:6.476 seconds]
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