Ashish,
It could be a couple of things. First, we’ve released a quickfix for 3.8.2 to fix a problem with the JSP Indexer. If you’re CPU is at 100% and you see a message in the bottom right corner of the window that says “JSP Indexing”, then the fix will help.
i have P3 512 MB ram Win 2K system and used to work pretty well with previous version
What was the “previous version”? Eclipse 2.0? If so, Eclipse 3.0 takes substantially more RAM on its own and yes, the heap does grow over time. I find the same issue with my workspace where I work on the MyEclipse plugins, so it doesn’t have MyEclipse installed. Personally, I simply restart Eclipse about once a day or so to reset the RAM. In MyEclipse, we’ve added a garbage collection menu item off the MyEclipse menu on the main menubar that you can run manually instead.