Re: January 2026 stabilization week

On Thu, Jan 29, 2026, at 3:47 AM, Olivier Certner wrote:
> 
> For now, it's either CPPC or powerd(8) (as for Intel), and a priori I'd recommend switching to CPPC entirely (once we have finished with the potential problems here).  For pressing production issues, in the meantime you can set the 'machdep.hwpstate_amd_cppc_enable' tunable to 0 to force using the "manual" P-states that powerd(8) can manipulate.
> 

On Intel, and now on AMD, it seems that CPPC is far worse than powerd (*).  By that I mean that low power settings use the same amount of power as powerd when ramped down, but limit the performance when a server is busy.   Conversely, midrange settings use more power than powerd and provide less performance.  And high settings use more power.

(*) At Netflix, we use a modified powerd, similar to powerdxx that takes multi-core load into account.

So the ability to let software control frequency is something that I don't want to loose.

Drew