Linux – CPU/JVM/JBoss 7 slows down over time

I'm experiencing performance slow down on JBoss 7.1.1 Final. I wrote simple program that demostrates this behavior. I generate an array of 100,000 of random integers and run bubble sort on it.

   @Model
   public class PerformanceTest {

      public void proceed() {
                long now = System.currentTimeMillis();
                int[] arr = new int[100000];
                for(int i = 0; i < arr.length; i++) {
                          arr[i] = (int) (Math.random() * 200000);
                }
                long now2 = System.currentTimeMillis();
                System.out.println((now2 - now) + "ms took to generate array");
                now = System.currentTimeMillis();
                bubbleSort(arr);
                now2 = System.currentTimeMillis();
                System.out.println((now2 - now) + "ms took to bubblesort array");
      }

      public void bubbleSort(int[] arr) {
                boolean swapped = true;
                int j = 0;
                int tmp;
                while (swapped) {
                          swapped = false;
                          j++;
                          for (int i = 0; i < arr.length - j; i++) {
                                    if (arr[i] > arr[i + 1]) {
                                              tmp = arr[i];
                                              arr[i] = arr[i + 1];
                                              arr[i + 1] = tmp;
                                              swapped = true;
                                    }
                          }
                }
      }

}

Just after I start the server, it takes approximately 22 seconds to run this code. After few days of JBoss 7.1.1. running, it takes 330 sec to run this code. In both cases, I launch the code when the CPU utilization is very low (say, 1%). Any ideas why? I run the server with following arguments:

-Xms1280m -Xmx2048m -XX:MaxPermSize=2048m -Djava.net.preferIPv4Stack=true -Dorg.jboss.resolver.warning=true -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true -Duser.timezone=UTC -Djboss.server.default.config=standalone-full.xml -Xrunjdwp:transport=dt_socket,address=8787,server=y,suspend=n

I'm running it on Linux 2.6.32-279.11.1.el6.x86_64 with java version "1.7.0_07".

It's within J2EE applicaiton. I use CDI so I have a button on JSF page that will call method "proceed" on @RequestScoped component PerformanceTest. I deploy this as separate war file and even if I undeploy other applications, it doesn't change the performance.

It's a virtual machine that is sharing CPUs with another machine but that one doesn't consume anything.

Here's yet another observation: when the server is after fresh start and I run the bubble sort, It utilizes 100% of one processor core. It never switches to another core or drops utilization below 95%. However after some time the server is running and I'm experiencing the performance problems, the method above is utilizing CPU core usually 100%, however I just found out from htop that this task is being switched very often to other cores. That is, at the beginning it's running on core #1, after say 2 seconds it's running on #5 then after say 2 seconds #8 etc. Furthermore, the utilization is not kept at 100% at the core but sometimes drops to 80% or even lower.

For the server after fresh start, even though If I simulate a load, it never switches the task to another core.