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

[Lucas Lima]

Em seg., 29 de jun. de 2026 às 11:05, Lukasz Luba
<lukasz.luba@xxxxxxx> escreveu:
>
>
>
> 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

Through my testings, HWP does seem follow an strictly non decreasing
duty-cycle to freq curve, with or without frequency clamping and turbo
boost activated. For me, that feels enough to justify the use of the
simplified energy model already implemented.