file: /proc/sys/vm/user_reserve_kbytes
variable: vm.user_reserve_kbytes
Official reference

When overcommit_memory is set to 2, “never overcommit” mode, reserve min(3% of current process size, user_reserve_kbytes) of free memory. This is intended to prevent a user from starting a single memory hogging process, such that they cannot recover (kill the hog).

user_reserve_kbytes defaults to min(3% of the current process size, 128MB).

If this is reduced to zero, then the user will be allowed to allocate all free memory with a single process, minus admin_reserve_kbytes. Any subsequent attempts to execute a command will result in “fork: Cannot allocate memory”.

Changing this takes effect whenever an application requests memory.