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    SubjectRe: [discussion]sched: a rough proposal to enable power saving in scheduler
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    On 21 August 2012 02:58, Alex Shi <alex.shi@intel.com> wrote:
    > On 08/20/2012 11:36 PM, Vincent Guittot wrote:
    >
    >>> > What you want it to keep track of a per-cpu utilization level (inverse
    >>> > of idle-time) and using PJTs per-task runnable avg see if placing the
    >>> > new task on will exceed the utilization limit.
    >>> >
    >>> > I think some of the Linaro people actually played around with this,
    >>> > Vincent?
    >> Sorry for the late reply but I had almost no network access during last weeks.
    >>
    >> So Linaro also works on a power aware scheduler as Peter mentioned.
    >>
    >> Based on previous tests, we have concluded that main drawback of the
    >> (now removed) old power scheduler was that we had no way to make
    >> difference between short and long running tasks whereas it's a key
    >> input (at least for phone) for deciding to pack tasks and for
    >> selecting the core on an asymmetric system.
    >
    >
    > It is hard to estimate future in general view point. but from hack
    > point, maybe you can add something to hint this from task_struct. :)
    >

    per-task load tracking patchsets give you a good view of the last dozen of ms

    >> One additional key information is the power distribution in the system
    >> which can have a finer granularity than current sched_domain
    >> description. Peter's proposal was to use a SHARE_POWERLINE flag
    >> similarly to flags that already describe if a sched_domain share
    >> resources or cpu capacity.
    >
    >
    > Seems I missed this. what's difference with current SD_SHARE_CPUPOWER
    > and SD_SHARE_PKG_RESOURCES.

    SD_SHARE_CPUPOWER is set in a sched domain at SMT level (sharing some
    part of the physical core)
    SD_SHARE_PKG_RESOURCES is set at MC level (sharing some resources like
    cache and memory access)

    >
    >>
    >> With these 2 new information, we can have a 1st power saving scheduler
    >> which spread or packed tasks across core and package
    >
    >
    > Fine, I like to test them on X86, plus SMT and NUMA :)
    >
    >>
    >> Vincent
    >
    >


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