linux-kernel - Re: [PATCH v2 0/7] cpufreq: intel_pstate: Enable EAS on hybrid platforms without SMT

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Message-ID: <CAJZ5v0hx+Ra0V7PBNZRKJ1wV-9J-FV5MFhVAsqUzpvHkfdN76Q@mail.gmail.com>
Date: Mon, 30 Jun 2025 20:51:29 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Ibrahim Ansari <ansari.ibrahim1@...il.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Linux PM <linux-pm@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>, 
	Peter Zijlstra <peterz@...radead.org>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Morten Rasmussen <morten.rasmussen@....com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, 
	Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, 
	Pierre Gondois <pierre.gondois@....com>, Christian Loehle <christian.loehle@....com>, 
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v2 0/7] cpufreq: intel_pstate: Enable EAS on hybrid
 platforms without SMT

Hi,

On Sun, Jun 29, 2025 at 2:28 PM Ibrahim Ansari
<ansari.ibrahim1@...il.com> wrote:
>
> Hi,
>
> On 5/13/25 19:31, Rafael J. Wysocki wrote:
>
> > Finally, schedutil needs to be the cpufreq governor which requires
> > intel_pstate to operate in the passive mode (schedutil is the default
> > governor in that case).  The most straightforward way to switch it
> > into the passive mode is to write "passive" to
> > /sys/devices/system/cpu/intel_pstate/status (it may also be started in
> > the passive mode as described in
> > https://www.kernel.org/doc/html/latest/admin-guide/pm/intel_pstate.html).
>
> I'm curious if you intend to bring back support for EAS with
> intel_pstate in active mode down the line?

No plans as of today and this is somewhat technically questionable
because EAS requires the schedutil governor for cpufreq which is only
available in the passive mode.

It may be revisited in the future, though, if there's sufficient demand.

> That would get this working out of the box across distros, since
> `intel_pstate=active` is the default setup everywhere (and typically
> what users should prefer? as I understand from the documentation.)

It's generally hard to say what users should prefer because it depends
on what they need.

The active mode involves less complexity in the kernel code and so it
is the default.  It is also somewhat performance-oriented relative to
EAS.

Users who prefer EAS can append intel_pstate=passive to the default
kernel command line.

> Thanks for your work!

Anytime!