Originally Posted by johnmccarthy
When the application ends the our RHEL 5 systems still run slow.
I doubt any real slow down lasts a significant time after the application ends.
I'm pretty sure you are misunderstanding memory statistics (seeing memory filled by buffers and cache) and expecting that to cause a slow down, and imagining the slow down you expect.
It is perfectly normal for buffers and cache to be filled up by some large applications. While there are ways to free that memory, freeing that memory will not improve system performance.
If you had interactive processes paused during the run of the big application, those will be slow to regain their memory after the big application ends. But they will be no faster (maybe even a little slower) at regaining their memory if you clear the cache at the end of running the big application.
Some commonly used applications might typically launch fast because their code is usually in cache. Running the big application might push those out of cache, so they launch slowly the next time they are run. Again, flushing cache after running the big application will not help (and might hurt).