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    SubjectRe: [discussion]sched: a rough proposal to enable power saving in scheduler
    On 08/15/2012 10:24 PM, Rakib Mullick wrote:

    > On 8/13/12, Alex Shi <alex.shi@intel.com> wrote:
    >> Since there is no power saving consideration in scheduler CFS, I has a
    >> very rough idea for enabling a new power saving schema in CFS.
    >>
    >> It bases on the following assumption:
    >> 1, If there are many task crowd in system, just let few domain cpus
    >> running and let other cpus idle can not save power. Let all cpu take the
    >> load, finish tasks early, and then get into idle. will save more power
    >> and have better user experience.
    >>
    > This assumption indirectly point towards the scheme when performance
    > is enabled, isn't it? Cause you're trying to spread the load equally
    > amongst all the CPUs.


    It is.

    >
    >>
    >> select_task_rq_fair()
    >> {

    int powersaving = 0;

    >> for_each_domain(cpu, tmp) {
    >> if (policy == power && tmp_has_capacity &&
    >> tmp->flags & sd_flag) {
    >> sd = tmp;
    >> //It is fine to got cpu in the domain

    powersaving = 1;

    >> break;
    >> }
    >> }
    >>
    >> while(sd) {
    if (policy == power && powersaving == 1)
    >> find_busiest_and_capable_group()
    >
    > I'm not sure what find_busiest_and_capable_group() would really be, it
    > seems it'll find the busiest and capable group, but isn't it a
    > conflict with the first assumption you proposed on your proposal?


    This pseudo code missed a power saving workable flag , adding it into
    above code should solved your concern.

    >
    > Thanks,
    > Rakib.




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