I just ran a quick benchmark and he's right. Here's what I got running stock downloads of each on the same PHP version, and both with XDebug running using Apache Bench with the following command
.
And here's the results that I got:
* CI 2.2.1 - 120.23 requests per second
* CI 3.0-RC3 - 65.07 requests per second.
What is causing it? Not sure yet - ran it through a quick profiler but it will take time to dig into things and find improvements. My guess is that we won't find too many improvements until after 3.0 is released since it's going out the door any day now.
Thanks for pointing this out, though.