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    SubjectRe: [PATCH 13/63] sched: numa: Mitigate chance that same task always updates PTEs
    On 10/07/2013 06:28 AM, Mel Gorman wrote:
    > From: Peter Zijlstra <peterz@infradead.org>
    >
    > With a trace_printk("working\n"); right after the cmpxchg in
    > task_numa_work() we can see that of a 4 thread process, its always the
    > same task winning the race and doing the protection change.
    >
    > This is a problem since the task doing the protection change has a
    > penalty for taking faults -- it is busy when marking the PTEs. If its
    > always the same task the ->numa_faults[] get severely skewed.
    >
    > Avoid this by delaying the task doing the protection change such that
    > it is unlikely to win the privilege again.

    > Signed-off-by: Peter Zijlstra <peterz@infradead.org>
    > Signed-off-by: Mel Gorman <mgorman@suse.de>

    Reviewed-by: Rik van Riel <riel@redhat.com>

    --
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