多线程文本处理的成本/收益

I am working on a real-time syntax highlighter for the iPhone and I have created a custom UIView that takes a string, parses it and then highlights it in its drawRect: method. I've also implemented a blinking cursor. However, it is starting to get a little slow and I think that when I implement multi-line processing and chunk-processing, it will slow it down more. However, I tried placing the I am working on a real-time syntax highlighter