[acon]

Saying that fork forces overcommit is strange. Fork is just one of the things that allocates memory. If you don't want overcommit fork should simply fail with ENOMEM if there isn't enough memory to back a copy of all the writable memory in the process.

[MichaelGG]

I meant the practical considerations of fork means overcommitment is needed in many cases where it otherwise wouldn't be needed. If you fork a 2GB process but the child only uses 1MB, you don't want to commit another 2GB for no reason.