That's because Windows forces you to use special userspace libraries that account for memory and let you create "reservations" for large regions, without actual

That's because Windows forces you to use special userspace libraries that account for memory and let you create "reservations" for large regions, without actually populating entries in the MMU (i.e. PML4t). Linux doesn't have that. You create reservations for large memory regions by allocating virtual memory, which of course doesn't become real (resident) until you use it. That's overcommit. But since there's no userspace libraries like WIN32 forced upon you on Linux, there's really no way for the kernel to know your intent when it comes to memory, because the abstractions for memory on Linux are so simple. Windows has a ridiculous byzantine system, which some people think is better. But people are really missing the point when they try to make an apples-to-apples comparison between the two systems of memory management. It's not a question of (a) overcommit good, vs. (b) overcommit bad. Anyone who thinks either is a fool. Linux is simply a system that requires a smart system administrator who understands your use cases and can tune sysctl accordingly when you want to push beyond the normal boundaries.