linux-kernel - Re: [PATCH] sched/deadline: Derive root domain from active cpu in task's cpus

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Message-ID: <20250930090441.GJ4067720@noisy.programming.kicks-ass.net>
Date: Tue, 30 Sep 2025 11:04:41 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: Pingfan Liu <piliu@...hat.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>
Subject: Re: [PATCH] sched/deadline: Derive root domain from active cpu in
 task's cpus_ptr

On Tue, Sep 30, 2025 at 08:20:06AM +0100, Juri Lelli wrote:

> I actually wonder if we shouldn't make cppc_fie a "special" DEADLINE
> tasks (like schedutil [1]). IIUC that is how it is thought to behave
> already [2], but, since it's missing the SCHED_FLAG_SUGOV flag(/hack),
> it is not "transparent" from a bandwidth tracking point of view.
> 
> 1 - https://elixir.bootlin.com/linux/v6.17/source/kernel/sched/cpufreq_schedutil.c#L661
> 2 - https://elixir.bootlin.com/linux/v6.17/source/drivers/cpufreq/cppc_cpufreq.c#L198

Right, I remember that hack. Bit sad its spreading, but this CPPC thing
is very much like the schedutil one, so might as well do that I suppose.