For JIT languages most of the code is dynamically generated, not available to be loaded back from the disk. Morealso, the allocations do happen at large chucks where the oom_killer also happens, so it's significantly less of an issue.

That doesn't necessarily improve matters. Now any code that gets JIT'd is also going to be permanently pinned in memory too, no matter whether it'll get used again, if you don't have swap.