Comment by tomsmeding

I've been doing some benchmarking recently and I've observed that on certain workloads, my CPU cores are not equivalent. (And this is an Intel CPU from 5 years ago, all cores are the same on paper.) In a particular very bad case I have a reproducible 50% performance difference between (physical) core 0 and core 5.

You might want to taskset to particular cores too, especially if you are looking at computational code with many almost-but-not-quite-random memory accesses.