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    SubjectRe: [patch 6/8] pull RT tasks
    Hi Steven,

    > When a pull RT is initiated, all overloaded runqueues are examined for
    > a RT task that is higher in prio than the highest prio task queued on the
    > target runqueue. If another runqueue holds a RT task that is of higher
    > prio than the highest prio task on the target runqueue is found it is pulled
    > to the target runqueue.

    I think, 2 things should be accomplished here :

    (1) be sure to pull the _highest_ prio task ;

    i.e. the _highest_ prio task amongst all runnable (but not running) RT
    tasks across all the run-queues which is capable of running on
    this_cpu ;

    (2) don't pull more than 1 task at once.

    that said, just pull the highest prio task and run it.

    ---

    why (2)? Just to avoid situations when tasks are being pulled/pushed
    back and forth between run-queues.

    Let's say we have 4 cpu system:

    0: task(10) , task(92)
    1: task(10), task(91)
    2: task(10), task(90)
    3: task(10)

    when task(10) on cpu#3 is inactive, we pull task(92), task(91),
    task(90) and then run task(90)... in the mean time, some of cpu[0..2]
    becomes inactive and pull task(91) and task(92) back and run them...
    that may repeat again and again depending on when/how long task(10)
    run on their corresponding cpus...

    so it seems to me that the more optimal behavior would be "don't pull
    more than you can run at the moment -- that's 1".

    to this goal, something like find_lock_highest_rq() would be necessary.

    and I guess, {get,put}_task_struct() should be used in pull_rt_task()
    for the 'next' in a similar way as it's done in push_rt_task() .


    >
    > [ ... ]
    >

    --
    Best regards,
    Dmitry Adamushko
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