Or: Hey, keeping the CPU busy for a given amount of time should be easy?

Welcome back to my blog. Last week, I showed you how to profile your Cloudfoundry application, and the week before, how I made the CPU-time profiler a tiny bit better by removing redundant synchronization. This week’s blog post will be closer to the latter, trying to properly waste CPU.

As a short backstory, my profiler needed a test to check that the queue size of the sampler really increased dynamically (see Java 25’s new CPU-Time Profiler: Queue Sizing (3)), so I needed a way to let a thread spend a pre-defined number of seconds running natively on the CPU. You can find the test case in its hopefully final form here, but be aware that writing such cases is more complicated than it looks.

So here we are: In need to essentially properly waste CPU-time, preferably in user-land, for a fixed amount of time. The problem: There are only a few scant resources online, so I decided to create my own. I’ll show you seven different ways to implement a simple

void my_wait(int seconds);

method, and you’ll learn far more about this topic than you ever wanted to. That works both on Mac OS and Linux. All the code is MIT licensed; you can find it on GitHub in my waste-cpu-experiments, alongside some profiling results.

As another tangent: Apparently, my Java 25’s new CPU-Time Profiler (1) blog post blew up on Hacker News. Fun times.