[quotemstr]

I don't like it when programs rely on VM overcommit in such a way that they break on other systems. Even if you don't care about Windows (which is a strict accounting no-overcommit system), you should care about Linux, which can be configured to do strict accounting the way Windows does.

If you want to use the big address-space carve-out trick, you can, but the right way to do it is to PROT_NONE the parts of the address space you aren't using and install a signal handler to commit bits of your carveout as they're used.

[JoshTriplett]

Processing a signal and mapping memory via that signal is less efficient than letting the kernel do it for you.

You'll get better performance by using userfaultfd.

[quotemstr]

That too, but if you commit in big enough chunks, you amortize the signal handling overhead down to almost nothing.