2018-04-25 MRI, the standard Ruby interpreter, has a serious problem with memory bloat in large Rails apps. It’s quite common for me to see Sidekiq processes which are 1-2GB in RSS or even larger! It turns out that a large part of this memory usage is due to memory fragmentation: MRI uses the OS’s memory allocator by default (on Linux, almost always GNU glibc), which seems to work poorly with Ruby