Re: January 2026 stabilization week

> 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.

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Olivier Certner