Text drawing is taking a lot on iPad using iOS 4.2 gm seed

I wrote an app which draws some text on the view using my own custom fonts, and the drawing takes about 200 ms on iPad with iOS 3.2, but after I installed iOS 4.2 BETA a month ago, it took more than 2 to 3 seconds to draw (10 - 15 times more), at that time I thought it's a BETA problem so I rolled back to iOS 3.2, then yesterday I installe开发者_开发知识库d the 4.2 GM Seed (which is considered as a final release) and the same problem happened,

Does anyone have an idea of what's going on?

Thank you for your help and good luck

Your best bet is to use the Sampler tool in Instruments.app (/Developer/Applications/Instruments.app) to determine where your time is being spent. Then you'll know what is actually slow, and you can optimize what you need to.