Date: Thu, 29 Jan 2026 22:09:47 +0100 From: Olivier Certner <olce@freebsd.org> To: Gleb Smirnoff <glebius@freebsd.org>, Drew Gallatin <gallatin@freebsd.org> Cc: freebsd-current@freebsd.org, src-committers@freebsd.org, ShengYi Hung <aokblast@freebsd.org> Subject: Re: January 2026 stabilization week Message-ID: <8518827.G18vQ0XA4d@ravel> In-Reply-To: <6197e075-212f-4260-b437-902e06d1002b@app.fastmail.com> References: <aXctKTNm_CEau0yB@cell.glebi.us> <2329920.sMrx5ctUpN@ravel> <6197e075-212f-4260-b437-902e06d1002b@app.fastmail.com>
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[-- Attachment #1 --] > On Intel, and now on AMD, it seems that CPPC is far worse than powerd (*). That must depend on workloads and objectives then, since I've had the opposite experience on laptops in terms of latency. > (...) And high settings use more power. But providing better performance, or not? > So the ability to let software control frequency is something that I don't want to loose. I certainly don't have plans to remove that. When talking about recommending CPPC, I was thinking about the default value we wanted to have for the new 'machdep.hwpstate_amd_cppc_enable' tunable, but not about removing it. IMO, this tunable is here to stay (it might just change form at some point). I also encourage you to give a shot at the patch in PR 292615, in order to see how the new knobs (min & max performance, desired performance) can affect your observations, even if after what you reported that may look unlikely. For the future, we should probably eye at teaching powerd(8) about working with CPPC, so that instead of trying to set frequencies directly (which cannot really work with and basically defeats the point of CPPC) it would instead tune the desired performance value (and possibly the min and max ones as well). Perhaps with that combination we could get the best of both worlds (software + hardware tuning), at least for some workloads. -- Olivier Certner [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- iQIzBAABCQAdFiEEmNCxHjkosai0LYIujKEwQJceJicFAml7zJwACgkQjKEwQJce JiderA//ag+G3V0bCU0s8VLLDaM5HFJ0M09NgK+ThVFi2dkA0W8Xn19bKYc+DdXp 0mqkCrmoYQfSOsl1gM1pm7GUvSc6tJMQPVweNCz5VoxMR+nr3V+DPBMej/+mbPS7 n+nEI6b9kWTeN2YiuIg3P61Mj2frxgHOfGgA+a8ACQN7NVvSDIWsEIckLL+pLPQP K5olc9SBnmKTRrng5OBPykZJlV/zLIwmNT+CuWk9YAdk9jGxVJHSUlt0o7H/r7WC /axL01gDVBNqK4jAv9aSrVoHmuelpjBczezhtR9HlBxhm0sAqvizqjH1XufEQux7 xLcClOzno33Uri/YP7r4jybpwx9zgQ+HqTWqOB/Bz7wJX49Y8W47GNmkZx2wLaWP vTdCQMOcnCkiyL9xK1nCnKtwCKg9u7PJGXIHngNklprcov59wLFiNY2IS9cmNUEH FmHB3KyBTnqt5+R0fXgz+xg6ttZGggYld7e8CZ+YtNfnq5JU8rEgIT7F2qp64SyP x6AnhzxJstBvIeQETJhO1I7RgQrIsFRJgzQ5QD9PRltM66St0ww/y5/xwfhXfDkC kAJ9VJCDkEQz/jqweo4WGUMcdzTVSQTNDqKu6fCnsnZUoZuYEJNfpMmPjaS4bIoT VnxRoXjH/uXP676BZEh147l5RJL7vXKZ7EvJ9Xruy1Cy7KA7Tw8= =vGnR -----END PGP SIGNATURE-----home | help
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