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    SubjectRe: [PATCH] sched: fix lose fair sleeper bonus in switch_to_fair()
    On Tue, Sep 08, 2015 at 04:04:49PM +0800, Wanpeng Li wrote:
    > >>However, if se->vruntime -= cfs_rq->min_vruntime is positive, the
    > >>behavior is different after your patch. e.g. se->vruntime(the
    > >>relative vruntime in switched_to_fair()) < min_vruntime -
    > >>sysctl_sched_latency/2
    > >>
    > >>before your patch:
    > >>
    > >>se->vruntime = min_vruntime - sysctl_sched_latency/2 (place_entity())
    > >my patch is based on ff277d4 commit at tip/sched/core.
    > >
    > >there's no change between before and after.
    > >
    > >check it please.
    > >
    > >and this logic seems to be no problem to me. :(
    >
    > Your logic will lose fair sleeper bonus in the scenario which I pointed out.

    i mean in ff277d4 commit:

    se->vruntime += cfs->min_vruntime (switched_to_fair())
    se->vruntime = se->vruntime or bonused value (place_entity())

    after my patch:

    se->vruntime += cfs->min_vruntime (switched_to_fair())
    se->vruntime = se->vruntime or bonused value (place_entity())

    ---

    SAME!!!

    in addtion, se->vruntime already had a bonused value if eligible,
    when it was detached from cfs_rq.

    >
    > >
    > >>after your patch:
    > >>
    > >>se->vruntime += cfs->min_vruntime (switched_to_fair())
    > >>se->vruntime = se->vruntime (place_entity())
    > >>
    > >>
    > >>Regards,
    > >>Wanpeng Li
    > >>
    > >>--
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