The problem is with how make checks which files have changed and the related I/O latency, plus the fact that pretty much everybody uses recursive make. The over

The problem is with how make checks which files have changed and the related I/O latency, plus the fact that pretty much everybody uses recursive make. The overhead of recursive make initialization plus the forced serialisation of builds is the main cause of slow make. Consider the Linux kernel as a contrast, which doesn't suffer from slow make because a lot of investment was made into a non-recursive make system. The fact that makefile generators like CMake tend to generate recursive makefiles is a shame.