linux-kernel - Re: [PATCH 0/3] pmdomain: Improve idlestate selection for CPUs

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Message-ID: <20251006-barnacle-of-pragmatic-faith-e6ca0d@sudeepholla>
Date: Mon, 6 Oct 2025 16:36:06 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Sudeep Holla <sudeep.holla@....com>, Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Maulik Shah <quic_mkshah@...cinc.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] pmdomain: Improve idlestate selection for CPUs

On Fri, Oct 03, 2025 at 05:02:42PM +0200, Ulf Hansson wrote:
> Platforms using the genpd governor for CPUs are relying on it to find the most
> optimal idlestate for a group of CPUs. Although, observations tells us that
> there are some significant improvement that can be made around this.
> 
> These improvement are based upon allowing us to take pending IPIs into account
> for the group of CPUs that the genpd governor is in control of. If there is
> pending IPI for any of these CPUs, we should not request an idlestate that
> affects the group, but rather pick a shallower state that affects only the CPU.
>

Thinking about this further, I’m not sure this issue is really specific to
pmdomain. In my view, the proposed solution could apply equally well to
platforms that don’t use pmdomain for cpuidle. Also, I don’t see why the
solution needs to be architecture-specific.

Thoughts ?

I understand it won’t handle all IPI cases, but generic helpers like
local_softirq_pending() and irq_work_needs_cpu()
should already cover some of them in a platform-independent way.

-- 
Regards,
Sudeep