blur computation costs

[mgutz]

I'm tweaking blur settings. What are the computational costs of each setting in descending order? Am I right in thinking that passes is 1 and size is 2? What about others?

[vaxerski]

passes will exponentially cost performance when the blur is redrawn (either background changes, e.g. your wallpaper or you have a floating window)

size will linearly cost performance.