Matlab to slow for arduino ?

Hello everybody. I make small project in matlab-simulink program with arduino board. I made self balancing robot with accelerometer and two dc motor but. The simulink is too slow as i guess cause it doesent work well. how can i make faster my program ? and also read value from accelerometer as fast as its possible. 2.I also tried use encoder but also simulink can't read as fast as i need simulink lose a lot of impulses. Anybody can help me with this problem ?