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    Subjectnewidle balancing in NUMA domain?

    I wonder why it was decided to do newidle balancing in the NUMA
    domain? And with newidle_idx == 0 at that.

    This means that every time the CPU goes idle, every CPU in the
    system gets a remote cacheline or two hit. Not very nice O(n^2)
    behaviour on the interconnect. Not to mention trashing our
    NUMA locality.

    And then I see some proposal to do ratelimiting of newidle
    balancing :( Seems like hack upon hack making behaviour much more

    One "symptom" of bad mutex contention can be that increasing the
    balancing rate can help a bit to reduce idle time (because it
    can get the woken thread which is holding a semaphore to run ASAP
    after we run out of runnable tasks in the system due to them
    hitting contention on that semaphore).

    I really hope this change wasn't done in order to help -rt or
    something sad like sysbench on MySQL.

    And btw, I'll stay out of mentioning anything about CFS development,
    but it really sucks to be continually making significant changes to
    domains balancing *and* per-runqueue scheduling at the same time :(
    It makes it even difficult to bisect things.


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      Last update: 2009-11-23 12:25    [W:0.036 / U:130.576 seconds]
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