Adobe has posted (link no longer works) a ColdFusion 9 Performance Brief, outlining several performance improvements over ColdFusion 7 and 8. The brief reports a 40% performance improvement over ColdFusion 8, and a 500% improvement over ColdFusion 7, running CanvasWiki.
If you heavily use CFC's, or the CreateUUID function you should see some significant performance improvements. Here's a summary of some of the more significant improvements:
- CFC Object Creation - 700% improvement over CF8
- CFC Method Invocation - 200% improvement over CF8
- Flash Remoting - 800% improvement over CF8
- UUID key generator / CreateUUID - 10,000% improvement over CF8
- IIS Connector Performance Improvement - 100% improvement over CF8. When a connector receives a request in ColdFusion 9, it picks the native thread from its thread pool and returns the IIS worker thread with IO Completion (the request will be in IO block state). Once the IIS request is freed from the request, it is immediately available to handle the next request and to serve pages of other content types. Once the request is completed by ColdFusion, the connector thread is returned to its native thread pool.
Another improvement of note is the Cache Template in Request setting, which the report claims can boost performance 50x when enabled. This feature works like trusted cache for the life of the request, so it won't check file timestamps for updates more than once for the same file during a request when enabled. If you have trusted cache turned on, I don't expect there to be any additional performance gains from enabling this feature. It is enabled by default in CF9.