There are performance improvements, but the graph is actually pretty extreme. If you read the full discussion on twitter he reveals that it isn't a web server,

There are performance improvements, but the graph is actually pretty extreme. If you read the full discussion on twitter he reveals that it isn't a web server, but a server running CLI scripts constantly. It is entirely possible there was a performance improvement in one thing that was constantly running and it may not actually be an accurate representation of overall performance improvement in PHP 5.4.