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    SubjectRe: [PATCH 1/2] mm: Disable zone_reclaim_mode by default
    Hi,

    On 2014-04-07 23:34:27 +0100, Mel Gorman wrote:
    > zone_reclaim_mode causes processes to prefer reclaiming memory from local
    > node instead of spilling over to other nodes. This made sense initially when
    > NUMA machines were almost exclusively HPC and the workload was partitioned
    > into nodes. The NUMA penalties were sufficiently high to justify reclaiming
    > the memory. On current machines and workloads it is often the case that
    > zone_reclaim_mode destroys performance but not all users know how to detect
    > this. Favour the common case and disable it by default. Users that are
    > sophisticated enough to know they need zone_reclaim_mode will detect it.

    Unsurprisingly I am in favor of this.

    > Documentation/sysctl/vm.txt | 17 +++++++++--------
    > mm/page_alloc.c | 2 --
    > 2 files changed, 9 insertions(+), 10 deletions(-)

    But I think linux/topology.h's comment about RECLAIM_DISTANCE should be
    adapted as well.

    Thanks,

    Andres

    --
    Andres Freund http://www.2ndQuadrant.com/
    PostgreSQL Development, 24x7 Support, Training & Services


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