On my OS X, if I load a couple hundred modules into ghci as bytecode, text entry gets balky and laggy. So e.g. if I hold down a key, the letters will stream in but have frequent hiccups. This seems to adversely affect haskeline as well, such that, using vi mode, sometimes ^[ to move to command mode will be lost, or it will spontaneously go to insert mode, or ^[ followed by 'h' will be just beep and remain in insert mode. If I load most of the modules compiled, this doesn't happen, or at least is not nearly so bad. It doesn't seem to be due to background work by ghci or anything, because it doesn't matter how long I wait after loading the modules. My previous random guess was that increased memory use made the GC work more, and my pauses were due to major collections. But when I try on linux, ghci remains responsive no matter how many modules I load, so maybe it's an OS X only problem. Do any other OS X users see this effect?