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    SubjectRe: [PATCH 6/8] Add __GFP_OTHER_NODE flag
    On Mon, 21 Feb 2011, Andi Kleen wrote:

    > From: Andi Kleen <>
    > Add a new __GFP_OTHER_NODE flag to tell the low level numa statistics
    > in zone_statistics() that an allocation is on behalf of another thread.
    > This way the local and remote counters can be still correct, even
    > when background daemons like khugepaged are changing memory
    > mappings.
    > This only affects the accounting, but I think it's worth doing that
    > right to avoid confusing users.

    This makes the accounting worse, NUMA_LOCAL is defined as "allocation from
    local node," meaning it's local to the allocating cpu, not local to the
    node being targeted.

    Further, preferred_zone has taken on a much more significant meaning other
    than just statistics: it impacts the behavior of memory compaction and how
    long congestion timeouts are, if a timeout is taken at all, depending on
    the I/O being done on behalf of the zone.

    A better way to address the issue is by making sure preferred_zone is
    actually correct by using the appropriate zonelist to be passed into the
    allocator in the first place.

    > I first tried to just pass down the right node, but this required
    > a lot of changes to pass down this parameter and at least one
    > addition of a 10th argument to a 9 argument function. Using
    > the flag is a lot less intrusive.

    And adding a branch to every successful page allocation for statistics
    isn't intrusive?

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      Last update: 2011-02-22 22:45    [W:0.022 / U:17.820 seconds]
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