Hello, Today I was doing some experiment with CPython and PyPy. I was very impressed by the performance of PyPy, when it’s doing operations in user space, it was almost 20 times faster than CPython. Then I decided to switch our Python CLI to PyPy and I run one of our major command in our CLI and results were worse than CPython. It got slower! Then I started to research it more. Our CLI’s characteristic is that it calls multiple other programs and read a lot of configuration data and create many files which mean all of those operations were related to sys calls. Then I run some simple test cases, tried to read and write millions of lines to a file or create and kill multiple processes. All of these operations were almost 5 times slower than CPython. I run my tests both MacOS and RHEL with latest version of PyPy3.7 My question is that, is that something known? Or can it be some improvement area that can be contributed? Best, Emre Yavuz