3.0 significantly slower than previous versions?

i have just upgrade to ci 3.0 for few days. (just copy old code to new ci 3.0 folder then re-config)
When running with same config, i found out ci 3.0 run slower than 2.2 versions 

In ver 2.2:
code execute < 100ms
   

ver 3.0:
code execute > 1100ms
   

All external files in 2 versions return same loading time (few percent difference)
But time to execute code in ver 3.0 is ten times slower than 2.2.


It's not worth upgrading, if website need 1 second more to execute
Can anybody help me, please?