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    SubjectRe: sched: tweak select_idle_sibling to look for idle threads
    On Mon, May 02, 2016 at 04:50:04PM +0200, Mike Galbraith wrote:

    > Order is one thing, but what the old behavior does first and foremost
    > is when the box starts getting really busy, only looking at target's
    > sibling shuts select_idle_sibling() down instead of letting it wreck
    > things. Once cores are moving, there are no large piles of anything
    > left to collect other than pain.

    > Anyway, the has_idle_cores business seems to shut select_idle_sibling()
    > down rather nicely when the the box gets busy. Forcing either core,
    > target's sibling or go fish turned in a top end win on 48 rq/socket.

    FWIW making the select_idle_core() thing iterate in the old style (start
    at target and wrap around) did bring an improvement, even in the face of
    has_idle_cores; it shrank the hole between OLD_IDLE and
    IDLE_CORES+IDLE_SMT (my variant of your #if 1 thing), but did not
    completely eliminate it (for sysbench-psql-oltp).

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