Many people have already posted different kinds of microbenchmarking method for testing the size limits of various structures(e.g ROB, PRF). I recommend you to look at Henry Wong's blog post and also Maynard Handley's PDFs first. I got my idea from them and many others!

I found a slightly different variant based on them

Testing on Apple platform is always a hassle, and for my method we have to have a way to access the Performance counters directly in our microbenchmark. Dougall made a Kext for this purpose, basically what it does is to provide access to the configuration registers and so we can set the PMCs available for userspace access. And to make my life easier, I made a kext to pin the microbenchmark to