AMD Fast CPPC To Be Merged For Linux 6.11
As covered on Phoronix back in April, the AMD Fast CPPC functionality allows for better performance and power efficiency for some CPUs such as recent Ryzen (Zen 4) mobile processors. AMD Fast CPPC when supported by the CPU/platform allows for operating a tighter loop within the amd_pstate passive mode for more responsive CPU frequency / power state handling.
The Fast CPPC feature relies on architectural improvements with the processor to allow for higher performance at the same power level. The posted kernel patches allow the CPU frequency transition delay to be lowered from 1000 us to 600 us on systems with fast CPPC support. In turn depending upon the workload this can commonly lead to 0~2% better performance. On a performance-per-Watt basis some workloads can see as much as a 6% improvement. AMD's tests have been done for Fast CPPC using a Ryzen 7 7840HS APU. This Fast CPPC support on capable platforms is automatically utilized when upgrading to a kernel with the necessary support.
The AMD Fast CPPC support was submitted by AMD engineer Mario Limonciello for queuing in the power management "-next" branch ahead of the Linux 6.11 cycle. Not part of this pull request but separately are other AMD P-State driver improvements still pending such as improving support for heterogeneous CPU types that we're still waiting to see if will cross the finish line in time for the Linux 6.11 cycle too.
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