AMD P-State Linux Driver Updated With Precision Boost Control, Other Fixes

Back in Linux 5.17 the AMD P-State "amd_pstate" driver was introduced for Ryzen and EPYC systems as an alternative to the ACPU CPUFreq frequency scaling driver with an emphasis on delivering better power efficiency for modern AMD Zen 2 and newer systems. Since the mainlining there hasn't been too much change to this driver but now a new patch series has been sent out with some updates.

Earlier this year AMD made it easier to enable amd_pstate and there has been a few patches here and there, but no major improvements to AMD P-State since its mainline arrival. Meanwhile, ACPI CPUFreq has tended to perform better still in benchmarks when it comes to raw performance / throughput.

Out today though is a new patch series from AMD with updates to this CPU power management driver. First up, the new patches add support for the Precision Boost hardware control with AMD processors. AMD Precision Boost is the fine-grained frequency control mechanism for optimizing power/performance. (There is Precision Boost Overdrive - PBO - as an extension to that for allowing optionally exceeding the rated power specifications of the platform.)

With the patches sent out today, the AMD Precision Boost support can be controlled when using amd-pstate by way of the /sys/devices/system/cpu/cpufreq/boost sysfs interface for monitoring the status or forcing it on/off in real-time.

In addition to the AMD Precision Boost control, the patch series also fixes an issue around the wrong lowest performance value reading, shortening the frequency transition delay time, and other fixes/clean-ups.

The updated patch series can be found on the mailing list for review. I'll be running some tests shortly of these new AMD P-State patches.