Collaborative Processor Performance Control (CPPC) CPPC defined in the ACPI spec describes a mechanism for the OS to manage theperformance of a logical processor on a contigious and abstract performancescale. CPPC exposes a set of registers to describe abstract performance scale,to request performance levels and to measure per-cpu delivered performance. For more details on CPPC please refer to the ACPI specification at: http://uefi.org/specifications Some of the CPPC registers are exposed via sysfs under: /sys/devices/system/cpu/cpuX/acpi_cppc/ for each cpu X -------------------------------------------------------------------------------- $ ls -lR  /sys/devices/system/cpu/cpu0/acpi_cppc//sys/devices/system/cpu/cpu0/acpi_cppc/:total 0-r--r--r-- 1 root root 65536 Mar  5 19:38 feedback_ctrs-r--r--r-- 1 root root 65536 Mar  5 19:38 highest_perf-r--r--r-- 1 root root 65536 Mar  5 19:38 lowest_freq-r--r--r-- 1 root root 65536 Mar  5 19:38 lowest_nonlinear_perf-r--r--r-- 1 root root 65536 Mar  5 19:38 lowest_perf-r--r--r-- 1 root root 65536 Mar  5 19:38 nominal_freq-r--r--r-- 1 root root 65536 Mar  5 19:38 nominal_perf-r--r--r-- 1 root root 65536 Mar  5 19:38 reference_perf-r--r--r-- 1 root root 65536 Mar  5 19:38 wraparound_time -------------------------------------------------------------------------------- * highest_perf : Highest performance of this processor (abstract scale).* nominal_perf : Highest sustained performance of this processor (abstract scale).* lowest_nonlinear_perf : Lowest performance of this processor with nonlinear  power savings (abstract scale).* lowest_perf : Lowest performance of this processor (abstract scale). * lowest_freq : CPU frequency corresponding to lowest_perf (in MHz).* nominal_freq : CPU frequency corresponding to nominal_perf (in MHz).  The above frequencies should only be used to report processor performance in  freqency instead of abstract scale. These values should not be used for any  functional decisions. * feedback_ctrs : Includes both Reference and delivered performance counter.  Reference counter ticks up proportional to processor's reference performance.  Delivered counter ticks up proportional to processor's delivered performance.* wraparound_time: Minimum time for the feedback counters to wraparound (seconds).* reference_perf : Performance level at which reference performance counter  accumulates (abstract scale). -------------------------------------------------------------------------------- 		Computing Average Delivered Performance Below describes the steps to compute the average performance delivered by takingtwo different snapshots of feedback counters at time T1 and T2. T1: Read feedback_ctrs as fbc_t1    Wait or run some workloadT2: Read feedback_ctrs as fbc_t2 delivered_counter_delta = fbc_t2[del] - fbc_t1[del]reference_counter_delta = fbc_t2[ref] - fbc_t1[ref] delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta