linux-kernel - Re: [PATCH v2] PM: EM: Add inotify support when the energy model is updated.

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Message-ID: <90834b07-9261-4be6-a10b-88d3f5308e1e@igalia.com>
Date: Sat, 10 May 2025 14:07:45 +0900
From: Changwoo Min <changwoo@...lia.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Lukasz Luba <lukasz.luba@....com>
Cc: christian.loehle@....com, tj@...nel.org, pavel@...nel.org,
 kernel-dev@...lia.com, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, len.brown@...el.com
Subject: Re: [PATCH v2] PM: EM: Add inotify support when the energy model is
 updated.

Thank you, Rafael, for the pointer.

On 5/10/25 01:41, Rafael J. Wysocki wrote:
>>
>> I have discussed that with Rafael and we have similar view.
>> The EM debugfs is not the right interface for this purpose.
>>
>> A better design and mechanism for your purpose would be the netlink
>> notification. It is present in the kernel in thermal framework
>> and e.g. is used by Intel HFI
>> - drivers/thermal/intel/intel_hfi.c
>> - drivers/thermal/thermal_netlink.c
>> It's able to send to the user space the information from FW about
>> the CPUs' efficiency changes, which is similar to this EM modification.
> 
> In addition, after this patch
> 
> https://lore.kernel.org/linux-pm/3637203.iIbC2pHGDl@rjwysocki.net/
> 
> which is about to get into linux-next, em_dev_update_perf_domain()
> will not be the only place where the Energy Model can be updated.

I am curious about whether the energy mode is likely to be updated more
often with this change. How often the energy model is likely to be
updated is the factor to be considered for the interface and the model
to post-processing the eneergy model (in the BPF schedulers).

Regards,
Changwoo Min

> 
> Thanks!
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