I think in that case overcommit will happily say the allocation worked. Unless you also zero the entire chunk of memory and then get OOM killed on the write.
I suppose you can try to reliable target "seriously wild allocation fails" without leaving too much memory on the table.
0: Heuristic overcommit handling. Obvious overcommits of
address space are refused. Used for a typical system. It
ensures a seriously wild allocation fails while allowing
overcommit to reduce swap usage. root is allowed to
allocate slightly more memory in this mode. This is the
default.
I suppose you can try to reliable target "seriously wild allocation fails" without leaving too much memory on the table.
https://www.kernel.org/doc/Documentation/vm/overcommit-accou...Running in an environent without overcommit would allow you to handle it gracefully though, although bringing its own zoo of nasty footguns.
See this recent discussion on what can happen when turning off overcommit:
https://news.ycombinator.com/item?id=46300411