[senfiaj]

I think Windows also uses something similar to Linux memory overcommit (maybe call it "lazy page allocation"), but probably all the available virtual memory is backed by the page file, the OS has limit for the allocation size and all the edge cases are handled well under low memory conditions. For example, think about stack memory. Megabytes of stack space can be reserved for each thread, but since programs rarely use the whole stack, it's not rational to immediately allocate all the physical pages, it will waste a lot of memory (especially for multi-threaded programs). The stack grows on demand when the program hits a guard page.

In short, Windows partially does the same lazy thing but unlike Linux with its optimistic overcommit, it is stricter about commit/backing-budget reservation.

[0x1d7]

Windows will never overcommit. All pages are backed by physical memory or backing store.

[senfiaj]

Yes, that was my point. But Windows might still allocate pages lazily (i.e. reserve them and actually allocate only when the program writes into them). The difference from Linux is that it will only reserve if the allocation has a reasonable size and the total committed allocation doesn't exceed certain safe limits / quotas, so it will be possible to safely swap on disk later under low memory conditions.