Consider appropriate hardware counters. (Note that multiplexing to measure more then three(?) at once can be misleading.) At least for serial code on x86, the

Consider appropriate hardware counters. (Note that multiplexing to measure more then three(?) at once can be misleading.) At least for serial code on x86, there's "top-down performance analysis". Some tools (I know Maqao) suggest how to address bottlenecks.