Eclipse Helios periodically starts running a job which displays "Computing additional info". During this time, Eclipse is very sluggish, bordering on unusable. What does this job do? Can I shut it off?
I just hope that someone in the JDT team comes to sense and gets rid of it, make it go faster, or at the very least change it to something meaningful.
Maybe this bug is related: Bug 293856 - [Browser] "Computing additional info" lag during content assist executions
Other than that:
Disable the virus scanner for Eclipse files (projects and the folder where Eclipse is installed). On demand scanning can cause severe performance problems with Java's lazy loading.
Disable all plugins that you don't need.
Give Eclipse more RAM (512MB or more)
Put 4GB of RAM into your computer. Costs nothing (