Messages in this thread | | | Subject | Re: [PATCH 2/2] sched/fair: Scale wakeup granularity relative to nr_running | From | Mike Galbraith <> | Date | Tue, 21 Sep 2021 07:50:07 +0200 |
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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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