Most major linux distros default to "heuristic overcommit", aka vm.overcommit_memory=0. The intent being to refuse obviously excessive allocations without sticking to a strict limit.

You can also enable behaviour like you describe by setting overcommit_memory=2 and some ratio overcommit_ratio (default 50) or exact number of kbytes overcommit_kbytes

Source: https://www.kernel.org/doc/Documentation/vm/overcommit-accou... https://www.kernel.org/doc/Documentation/sysctl/vm.txt