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Hi all, The LLVM benchmarking system produces very noisy results even on quiet machines. One of the sources of inaccuracy is the timing tool we are using. Because it is a user-space tool, the OS can context switch it and we will get an outlier result. Perf stat uses SW_TASK_CLOCK counter in kernel to measure time, therefore more accurate. It also does not get context switched. I've implemented a wrapper script over perf stat which mimics the behaviour of timeit tool in test suite, so that nothing else needs to be modified. The script is not yet feature complete as time...

...> The LLVM benchmarking system produces very noisy results even on >> quiet >> machines. One of the sources of inaccuracy is the timing tool we are >> using. Because it is a user-space tool, the OS can context switch it >> and we will get an outlier result. Perf stat uses SW_TASK_CLOCK >> counter in kernel to measure time, therefore more accurate. It also >> does not get context switched. >> >> I've implemented a wrapper script over perf stat which mimics the >> behaviour of timeit tool in test suite, so that nothing else needs to >> be mod...

...oduces very noisy results even on >> >> quiet >> >> machines. One of the sources of inaccuracy is the timing tool we are >> >> using. Because it is a user-space tool, the OS can context switch it >> >> and we will get an outlier result. Perf stat uses SW_TASK_CLOCK >> >> counter in kernel to measure time, therefore more accurate. It also >> >> does not get context switched. >> >> >> >> I've implemented a wrapper script over perf stat which mimics the >> >> behaviour of timeit tool in test suite,...