alt Hacker NewsWhat about an architecture, where there are pages and access permissions, but no translation (virtual address is always equal to physical)? fork() would become impossible, but Windows is fine without it anyway.
What about an architecture, where there are pages and access permissions, but no translation (virtual address is always equal to physical)? fork() would become impossible, but Windows is fine without it anyway.
You are describing a memory protection unit (MPU). Those are common in low-resource contexts that are too simple to afford a full memory management unit (MMU). The problem with scaling that up, especially in general-purpose environments with dynamic process creation, is fragmentation of the shared address space.
You need a contiguous chunk for whatever object you are allocating. Other allocations fragment the address space, so there might be adequate space in total, but no individual contiguous chunk is large enough. You need to move around the backing storage, but then that makes your linear addresses non-stable. You solve that by adding a indirection layer mapping your "address", which is really a key/ID, to the backing storage. At that point you are basically back to a MMU.