Re: [PATCH] sched/topology: Allow EAS without schedutil for artificial Energy Models

[Lukasz Luba <lukasz.luba@arm.com>]

On 6/29/26 09:35, Lucas de Lima Nóbrega wrote:
> EAS currently refuses to enable energy-aware scheduling on a root
> domain unless schedutil is the active CPUFreq governor for all of its
> CPUs (cpufreq_ready_for_eas()). This requirement exists to protect the
> accuracy of the energy estimate: EAS predicts the OPP a CPU will run
> at from its utilization, which is only meaningful if the active
> governor actually requests OPPs that way, and schedutil is the only
> one that does.
> 
> That requirement does not apply to artificial Energy Models
> (EM_PERF_DOMAIN_ARTIFICIAL). An artificial EM is built from a
> get_cost() callback instead of real power numbers, and only encodes a
> cost ranking between CPUs (e.g. P-cores cost more than E-cores at a
> given utilization). It never claims to predict real energy use at any
> specific OPP, so there is no per-OPP accuracy for the governor
> requirement to protect, regardless of which governor is in control or
> whether it tracks utilization at all.
> 
> intel_pstate registers exactly this kind of artificial EM for hybrid
> (P/E-core) systems without SMT, regardless of whether it operates in
> active or passive mode. In active mode it never uses schedutil, since
> HWP picks frequency autonomously, so on these systems EAS never

When frequency is picked autonomously then EAS and energy estimations
don't make sense IMHO.

Do you have any data from experiments how it runs?

Regards,
Lukasz