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    SubjectRe: [PATCH 2/2] sched/fair: Scale wakeup granularity relative to nr_running
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    On Tue, 2021-09-21 at 05:52 +0200, Mike Galbraith wrote:
    > On Mon, 2021-09-20 at 15:26 +0100, Mel Gorman wrote:
    >
    >
    > The scaled up tweakables on my little quad desktop box:
    > sched_nr_latency = 8
    > sched_wakeup_granularity = 4ms
    > sched_latency = 24ms
    >
    > Due to the FAIR_SLEEPERS feature, a task can only receive a max of
    > sched_latency/2 sleep credit, ie the delta between waking sleeper and
    > current is clipped to a max of 12 virtual ms, so the instant our
    > preempt threshold reaches 12.000ms, by human booboo or now 3 runnable
    > tasks with this change, wakeup preemption is completely disabled, or?

    I just dug up a now ancient artifact testcase allegedly distilled from
    a real application's control thread sometime back in the dark ages, and
    granularity >= latency/2 still does turn off wakeup preemption.

    -Mike

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