linux-kernel - Re: [PATCH 00/11] PM: EM: Add netlink support for the energy model.

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Message-ID: <94c5c8c7-be07-4c26-ac39-8123410b0402@arm.com>
Date: Mon, 2 Jun 2025 12:52:43 +0100
From: Lukasz Luba <lukasz.luba@....com>
To: Changwoo Min <changwoo@...lia.com>
Cc: christian.loehle@....com, tj@...nel.org, pavel@...nel.org,
 len.brown@...el.com, rafael@...nel.org, kernel-dev@...lia.com,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 00/11] PM: EM: Add netlink support for the energy model.

Hi Changwoo,

On 5/29/25 01:13, Changwoo Min wrote:
> There is a need to access the energy model from the userspace. One such
> example is the sched_ext schedulers [1]. The userspace part of the
> sched_ext schedules could feed the (post-processed) energy-model
> information to the BPF part of the scheduler.
> 
> Currently, debugfs is the only way to read the energy model from userspace;
> however, it lacks proper notification mechanisms when a performance domain
> and its associated energy model change.
> 
> This patch set introduces a generic netlink for the energy model, as
> discussed in [2]. It allows a userspace program to read the performance
> domain and its energy model. It notifies the userspace program when a
> performance domain is created or deleted or its energy model is updated
> through a multicast interface.
> 
> Specifically, it supports two commands:
>    - EM_GENL_CMD_PD_GET_ID: Get the list of information for all performance domains.
>    - EM_GENL_CMD_PD_GET_TBL: Get the energy model table of a performance domain.
> 
> Also, it supports three notification events:
>    - EM_GENL_EVENT_PD_CREATE: When a performance domain is created.
>    - EM_GENL_EVENT_PD_DELETE: When a performance domain is deleted.
>    - EM_GENL_EVENT_PD_UPDATE: When the energy model table of a performance domain is updated.
> 
> The userspace code example using the EM netlink interface is at [3].
> 
> [1] https://lwn.net/Articles/922405/
> [2] https://lore.kernel.org/lkml/a82423bc-8c38-4d57-93da-c4f20011cc92@arm.com/
> [3] https://github.com/multics69/em-netlink/tree/patch-v1

Thanks for the patch set and for the reference code in user-space.
I will give it a try and then do the review.

Regards,
Lukasz