benchmarking - Linux: CPU benchmark requiring longer time and different CPU utilization levels

Question

For my research I need a CPU benchmark to do some experiments on my Ubuntu laptop (Ubuntu 15.10, Memory 7.7 GiB, Intel Core i7-4500U CPU @ 1.80HGz x 4, 64bit). In an ideal world, I would like to have a benchmark satisfying the following:

1. The CPU should be an official benchmark rather than created by my own for transparency purposes.
2. The time needed to execute the benchmark on my laptop should be at least 5 minutes (the more the better).
3. The benchmark should result in different levels of CPU throughout execution. For example, I don't want a benchmark which permanently keeps the CPU utilization level at around 100% - so I want a benchmark which will make the CPU utilization vary over time.

Especially points 2 and 3 are really key for my research. However, I couldn't find any suitable benchmarks so far. Benchmarks I found so far include: sysbench, CPU Fibonacci, CPU Blowfish, CPU Cryptofish, CPU N-Queens. However, all of them just need a couple of seconds to complete and the utilization level on my laptop is at 100% constantly.

Question: Does anyone know about a suitable benchmark for me? I am also happy to hear any other comments/questions you have. Thank you!

Answer 1

To choose a benchmark, you need to know exactly what you're trying to measure. Your question doesn't include that, so there's not much anyone can tell you without taking a wild guess.

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If you're trying to measure how well Turbo clock speed works to make a power-limited CPU like your laptop run faster for bursty workloads (e.g. to compare Haswell against Skylake's new and improved power management), you could just run something trivial that's 1 second on, 2 seconds off, and count how many loop iterations it manages.

The duty cycle and cycle length should be benchmark parameters, so you can make plots. e.g. with very fast on/off cycles, Skylake's faster-reacting Turbo will ramp up faster and drop down to min power faster (leaving more headroom in the bank for the next burst).

The speaker in that talk (the lead architect for power management on Intel CPUs) says that Javascript benchmarks are actually bursty enough for Skylake's power management to give a measurable speedup, unlike most other benchmarks which just peg the CPU at 100% the whole time. So maybe have a look at Javascript benchmarks, if you want to use well-known off-the-shelf benchmarks.

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If rolling your own, put a loop-carried dependency chain in the loop, preferably with something that's not too variable in latency across microarchitectures. A long chain of integer adds would work, and Fibonacci is a good way to stop the compiler from optimizing it away. Either pick a fixed iteration count that works well for current CPU speeds, or check the clock every 10M iterations.

Or set a timer that will fire after some time, and have it set a flag that you check inside the loop. (e.g. from a signal handler). Specifically, alarm(2) may be a good choice. Record how many iterations you did in this burst of work.