No more missing minutes in your profiling data! The tsc_freq_khz module provides a way to read the actual TSC frequency. This assumption is wrong on newer CPUs, and leads to improper time measurement. X-Ray uses the x86 Time Stamp Counter (TSC), a low-latency monotonically increasing clock, to measure event duration, and assumes that TSC frequency is equivalent to maximum clock speed. The tsc_freq_khz module also makes these tools more accurate on newer Intel processors.
No more “Unable to determine CPU frequency” errors! The tsc_freq_khz module enhances the performance of profiling and benchmarking tools like X-Ray in virtualized environments. We’ll take a quick but deep dive into x86 timers to explain the problem, but first, let’s get to the goods. Well, we’ve run into both situations, so we built a solution in the form of a Linux kernel module called tsc_freq_khz.
Or worse, have you profiled every function in an application, only to find the sum of all function runtimes accounted for ~15 minutes of a 20-minute run? Where did those five minutes go!? =65892=Unable to determine CPU frequency. Have you ever tried using LLVM’s X-Ray profiling tools to make some flame graphs, but gotten obscure errors like: =65892=Unable to determine CPU frequency for TSC accounting.
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