New kernel patches by AMD for the Linux kernel provide "frequency sensitivity feedback" for the powersave bias in cpufreq
. This hardware feedback feature is to be introduced on future AMD processors.
This patch-set allows the system to make more power conscious frequency changing decisions based upon hardware feedback. The hardware bits are to be found on "AMD Family 16h" processors and above, which is the forthcoming AMD "Jaguar"
product. AMD provided the original Linux kernel support
for "Family 16h" at the end of 2012.
Jacob Shin of AMD explains this new power-saving capability, "Hardware feedback tells software how 'sensitive' to frequency changes the workloads are. CPU-bound workloads will be more sensitive -- they will perform better as frequency increases. Memory/IO-bound workloads will be less sensitive -- they will not necessarily perform better as frequency increases. This patchset was compared against ondemand governor without powersave bias and did not show any performance degradation on CPU-bound workloads such as kernbench and unixbench. While saving power on Memory-bound workloads such as stream."
This AMD-specific powersave bias will likely be merged into the Linux 3.10 kernel. The patch series can be found on the kernel mailing list
. Too bad AMD doesn't have any Radeon graphics power management improvements for their open-source driver.