> All `ps` is doing is reading files in proc. The memory info it prints is in `/proc/$pid/status`. Ruby can trivially read `/proc/self/status` to get that very naive view of how much memory it's using.

Yep, great point, I am simply wrong about this.

> I believe she meant the operating system's copy-on-write of memory. Forking a copy of a process is actually very cheap because it's copy-on-write. That has nothing to do with ruby or its version and has been true in linux for as long as linux has existed.

Re: Copy on write the way Ruby implements GC in < 2.0 screws this up:

> The way ruby creates objects, the GC flag or reserved bit is stored in the object itself. So, as you would have guessed by now, when the GC runs in one of the processes, the GC flag would be modified in all the objects even if they are present in the shared pool. Now, the OS would sense this and trigger a copy-on-write making private copies of the objects in each child’s memory space.

https://medium.com/@rcdexta/whats-the-deal-with-ruby-gc-and-...