Notes about APERF and MPERF
本文将mark下Intel APERF(Actual Performance Frequency Clock Count)和MPERF(Maximum Performance Frequency Clock Count)的相关notes。
介绍
There are two model-specific registers (MSRs) on modern x86 CPUs called APERF and MPERF. Both can be thought of as a sort of time-stamp counter that increments as the CPU executes. MPERF increments at constant a rate proportional to the maximum frequency of the processor, while APERF increments at a variable rate proportional to the actual operating frequency. If aperf_change is the change in APERF over a given time period, and mperf_change is the change in MPERF over that same period, then the operating frequency can be approximated as:
1 | operating_freq = (max_freq * aperf_change) / mperf_change; |
总结
基于APERF和MPERF，可以测量CPU的实际频率。
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