I think I agree with you, but would like to add that from reading the blog post, it sounds like Windows is actually doing this better than both Linux and Solari

I think I agree with you, but would like to add that from reading the blog post, it sounds like Windows is actually doing this better than both Linux and Solaris (but my knowledge is a bit limited in this area). I don't quite like the overcommit approach nor the "all address space must be reserved in swap" approach, because both can fail badly in some reasonable scenarios. I think having a separate system call to commit/uncommit memory like Windows seems to have is probably a better approach than just having mmap()/munmap() system calls (without a way of communicating with the kernel about which parts of the allocated space you are using), because then you can have the advantages of sparse address space usage while not having the drawbacks of having the OS kill innocent processes. This would also have the advantage that in fork(), the kernel would just need to reserve swap space for the amount of committed memory, not the amount of allocated address space, the latter of which could be much larger (by orders of magnitude).