Hi, in an application of mine I start a long-running operation in a thread via forkIO so that the UI process doesn't get blocked. It just so happens, that the long-running process also takes the CPU to nearly 100% while it runs. During that time the run-time system does *not* switch back and forth between the UI-process and the long-running task, it seems that the UI process only gets woken up *after* the high CPU thread finishes completely. To the effect of course that it makes no difference at all to the UIs responsiveness whether I use forkIO or not. The long running process is pretty atomic, it's a single query to the database which takes up to a minute to complete so I don't see a chance to squeeze a "mainIteration" in there. What can I do? Günther