Some tips for benchmarking

Rafael EspĂ­ndola via llvm-commits llvm-commits at
Wed Oct 19 19:39:39 PDT 2016

After much pain I decided that instead of just running tests many
times I should put some effort in figuring out why perf numbers were
so hard to reproduce on my machine.

I was already disabling address space randomization and setting the
scaling_governor to performance. Other things I found

* Use to reserve a cpu for just
the program you are benchmarking.
* Disable the SMP pair (echo 0 > /sys/devices/system/cpu/cpuX/online)
of the cpu you will use for the benchmark.
* disable turbo mode (echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo).

The results are pretty awesome:

3.012355647 seconds time elapsed         ( +-  0.01% )



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