Messages in this thread | | | Date | Mon, 16 Jan 2023 11:11:44 +0100 | Subject | Re: [PATCH] sched/idle: Make idle poll dynamic per-cpu | From | Daniel Bristot de Oliveira <> |
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On 1/16/23 10:51, Vincent Guittot wrote: > On Mon, 16 Jan 2023 at 10:28, Ingo Molnar <mingo@kernel.org> wrote: >> >> >> * Ingo Molnar <mingo@kernel.org> wrote: >> >>>> Urgh, can we please make this a cpuidle governor thing or so? So that >>>> we don't need to invent new interfaces and such. >>> >>> I think the desired property here would be to make this interface on top >>> of pretty much any governor. Ie. have a governor, but also a way to drop >>> any CPU into idle-poll, overriding that. >> >> ... with the goal of having the best governor for power efficiency by >> default - but also the ability to drop a handful of CPUs into the highest >> performance / lowest latency idle mode. >> >> It's a special kind of nested policy, for workload exceptions. > > User can set per cpu latency constraint with > /sys/devices/system/cpu/cpu*/power/pm_qos_resume_latency_us > Which is then used by cpuidle governor when selecting an idle state. > The cpuidle governor should then select the idle state that matches > with the wakeup latency for those CPUs but select the most power > efficient for others. Setting a low value should filter all idle > states except the polling one
Yep, that is a possibility, but it does not always work as expected. For example, on virtual machines the vCPU gets scheduled out, even with this option set :-/.
-- Daniel
> Regards > Vincent >> >> Thanks, >> >> Ingo
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