linux-kernel - Re: [PATCH v3] sched/topology: remove sysctl_sched_energy

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Date:   Thu, 14 Sep 2023 18:21:27 +0200
From:   Valentin Schneider <vschneid@...hat.com>
To:     Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>, mingo@...hat.com,
        peterz@...radead.org, vincent.guittot@...aro.org
Cc:     sshegde@...ux.vnet.ibm.com, dietmar.eggemann@....com,
        linux-kernel@...r.kernel.org, ionela.voinescu@....com,
        quentin.perret@....com, srikar@...ux.vnet.ibm.com,
        mgorman@...hsingularity.net, mingo@...nel.org,
        pierre.gondois@....com, yu.c.chen@...el.com,
        tim.c.chen@...ux.intel.com
Subject: Re: [PATCH v3] sched/topology: remove sysctl_sched_energy_aware
 depending on the architecture

On 13/09/23 17:18, Shrikanth Hegde wrote:
> sysctl_sched_energy_aware is available for the admin to disable/enable
> energy aware scheduling(EAS). EAS is enabled only if few conditions are
> met by the platform. They are, asymmetric CPU capacity, no SMT,
> valid cpufreq policy, frequency invariant load tracking. It is possible
> platform when booting may not have EAS capability, but can do that after.
> For example, changing/registering the cpufreq policy.
>
> At present, though platform doesn't support EAS, this sysctl is still
> present and it ends up calling rebuild of sched domain on write to 1 and
> NOP when writing to 0. That is confusing and un-necessary.
>

But why would you write to it in the first place? Or do you mean to use
this as an indicator for userspace that EAS is supported?