Or, you could just make a logging serial queue that you send all log messages to; that way there's no risk of activity on the main thread slowing down your logging. In (Obj-)C:

    static queue_t queue;
    void log (NSString *message) {
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            queue = dispatch_queue_create("logging", DISPATCH_QUEUE_SERIAL);
        });
        dispatch_async(queue, ^{
            NSLog(message);
        });
    }