Firstly, remember, this is not the default. With the overcommit_memory tunable set to 2, the formula used to calculate the total (possibly overcommitted) available memory is as follows:
Total available memory = (RAM + swap) * (overcommit_ratio/100);
This formula only applies when vm.overcommit == 2.
On our Fedora 31 VM, with vm.overcommit == 2 and 2 GB each of RAM and swap, this yields the following (in gigabytes):
Total available memory = (2 + 2) * (50/100) = 4 * 0.5 = 2 GB
This value – the (over)commit limit – is also seen in /proc/meminfo as the CommitLimit field.
