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    Subject[PATCH 4/6] cpuset write vmscan
    Direct reclaim: cpuset aware writeout

    During direct reclaim we traverse down a zonelist and are carefully
    checking each zone if its a member of the active cpuset. But then we call
    pdflush without enforcing the same restrictions. In a larger system this
    may have the effect of a massive amount of pages being dirtied and then either

    A. No writeout occurs because global dirty limits have not been reached


    B. Writeout starts randomly for some dirty inode in the system. Pdflush
    may just write out data for nodes in another cpuset and miss doing
    proper dirty handling for the current cpuset.

    In both cases dirty pages in the zones of interest may not be affected
    and writeout may not occur as necessary.

    Fix that by restricting pdflush to the active cpuset. Writeout will occur
    from direct reclaim the same way as without a cpuset.

    Signed-off-by: Christoph Lameter <>
    Acked-by: Ethan Solomita <>


    Patch against 2.6.23-rc4-mm1

    diff -uprN -X 0/Documentation/dontdiff 3/mm/vmscan.c 4/mm/vmscan.c
    --- 3/mm/vmscan.c 2007-09-11 14:41:56.000000000 -0700
    +++ 4/mm/vmscan.c 2007-09-11 14:50:41.000000000 -0700
    @@ -1301,7 +1301,8 @@ unsigned long do_try_to_free_pages(struc
    if (total_scanned > sc->swap_cluster_max +
    sc->swap_cluster_max / 2) {
    - wakeup_pdflush(laptop_mode ? 0 : total_scanned, NULL);
    + wakeup_pdflush(laptop_mode ? 0 : total_scanned,
    + &cpuset_current_mems_allowed);
    sc->may_writepage = 1;

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