I have fairly consistently suffered huge slow downs in Eclipse when it tries to validate JSF pages. I'm not sure exactly what the problem is or what triggers it but once Eclipse starts validating JSF it grinds to a near halt and strats throwing OOMEs my way. The quickest fix for this problem I have found is just to turn off validation. Right click on the project. Select preferences. Select Validation. Uncheck pretty much everything the important one being JSP. Enjoy a new faster Eclipse.