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    SubjectRe: [patch 01/15] sched: (fixlet) dont update shares twice on on_rq parent
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    On Tue, 2011-05-10 at 16:14 +0900, Hidetoshi Seto wrote:
    > (2011/05/03 18:28), Paul Turner wrote:
    > > In dequeue_task_fair() we bail on dequeue when we encounter a parenting entity
    > > with additional weight. However, we perform a double shares update on this
    > > entity since we continue the shares update traversal from that point, despite
    > > dequeue_entity() having already updated its queuing cfs_rq.
    > >
    > > Avoid this by starting from the parent when we resume.
    > >
    > > Signed-off-by: Paul Turner <pjt@google.com>
    > > ---
    > > kernel/sched_fair.c | 4 +++-
    > > 1 file changed, 3 insertions(+), 1 deletion(-)
    > >
    > > Index: tip/kernel/sched_fair.c
    > > ===================================================================
    > > --- tip.orig/kernel/sched_fair.c
    > > +++ tip/kernel/sched_fair.c
    > > @@ -1355,8 +1355,10 @@ static void dequeue_task_fair(struct rq
    > > dequeue_entity(cfs_rq, se, flags);
    > >
    > > /* Don't dequeue parent if it has other entities besides us */
    > > - if (cfs_rq->load.weight)
    > > + if (cfs_rq->load.weight) {
    > > + se = parent_entity(se);
    > > break;
    > > + }
    > > flags |= DEQUEUE_SLEEP;
    > > }
    > >
    >
    > Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    >
    > This small fixlet can stand alone.
    > Peter, how about getting this into git tree first?

    tip 2f36825b176f67e5c5228aa33d828bc39718811f contains the below.

    /* Don't dequeue parent if it has other entities besides us */
    - if (cfs_rq->load.weight)
    + if (cfs_rq->load.weight) {
    + /*
    + * Bias pick_next to pick a task from this cfs_rq, as
    + * p is sleeping when it is within its sched_slice.
    + */
    + if (task_sleep && parent_entity(se))
    + set_next_buddy(parent_entity(se));
    break;
    + }
    flags |= DEQUEUE_SLEEP;
    }



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