From: Russell Haley <yumpusamongus@gmail.com>
To: Shashank Balaji <shashank.mahadasyam@sony.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Jonathan Corbet <corbet@lwn.net>
Cc: linux-pm@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org,
Shinya Takumi <shinya.takumi@sony.com>
Subject: Re: [PATCH] cpufreq, docs: (userspace governor) add that actual freq is >= scaling_setspeed
Date: Thu, 22 May 2025 03:50:55 -0500 [thread overview]
Message-ID: <15871c67-0d18-430f-935e-261b2cda855b@gmail.com> (raw)
In-Reply-To: <20250522-userspace-governor-doc-v1-1-c8a038e39084@sony.com>
On 5/22/25 3:05 AM, Shashank Balaji wrote:
> The userspace governor does not have the CPUFREQ_GOV_STRICT_TARGET flag, which
> means the requested frequency may not strictly be followed. This is true in the
> case of the intel_pstate driver with HWP enabled. When programming the
> HWP_REQUEST MSR, the min_perf is set to `scaling_setspeed`, and the max_perf
> is set to the policy's max. So, the hardware is free to increase the frequency
> beyond the requested frequency.
>
> This behaviour can be slightly surprising, given the current wording "allows
> userspace to set the CPU frequency". Hence, document this.
>
In my opinion, the documentation is correct, and it is the
implementation in intel_pstate that is wrong. If the user wanted two
separate knobs that control the minimum and maximum frequencies, they
could leave intel_pstate in "active" mode and change scaling_min_freq
and scaling_max_freq.
If the user asks for the frequency to be set from userspace, the
frequency had damn well better be set from userspace.
- Russell
next prev parent reply other threads:[~2025-05-22 8:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-22 8:05 [PATCH] cpufreq, docs: (userspace governor) add that actual freq is >= scaling_setspeed Shashank Balaji
2025-05-22 8:50 ` Russell Haley [this message]
2025-05-22 9:46 ` Shashank Balaji
2025-05-22 9:56 ` Rafael J. Wysocki
2025-05-22 11:15 ` Russell Haley
2025-05-22 9:47 ` Rafael J. Wysocki
2025-05-22 11:15 ` Russell Haley
2025-05-22 11:54 ` Rafael J. Wysocki
2025-05-23 18:57 ` Rafael J. Wysocki
2025-05-23 4:25 ` Shashank Balaji
2025-05-23 19:06 ` Rafael J. Wysocki
2025-05-23 21:47 ` Russell Haley
2025-05-27 8:21 ` Shashank Balaji
2025-05-27 12:00 ` Rafael J. Wysocki
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=15871c67-0d18-430f-935e-261b2cda855b@gmail.com \
--to=yumpusamongus@gmail.com \
--cc=corbet@lwn.net \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=rafael@kernel.org \
--cc=shashank.mahadasyam@sony.com \
--cc=shinya.takumi@sony.com \
--cc=viresh.kumar@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).