Looks like you are following my instructions for graphing the GC data, but you incorrectly added the "after" and "millis" data points to the graph. When adding the extra data points, be sure to select the entire column and to place that selection in the "Y Values" box, and leave the "X Values" box blank. I suspect you switched the values of these two boxes. Based on the current graphs, I don't think that 1GB is a sufficient heap size, try 1.5GB. and increase the young gen size to 500MB. As to the response time differences, it could be the major GC time, but as I noted, the graphs are not correctly plotted so I cannot tell what the GC times are. You could, of course, scan the GC times for the major collections to see about how long each one takes. How many processors/cores are on your system? If you have several, you might try the CMS collection. Are you running a 32-bit or 64-bit JVM? View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4258646#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...