java process on windows using less memory than specified in -xms?

Question

I'm starting my server with "java -xms 1280m -xmx 1280m" command. On Linux machines, this works fine and I see the process using almost the same amount of memory. On Windows machines, however, I see the java process using much less than 1280m - around 500-600m. I gathered this data from the windows task manager, if that matters. The two windows machines I checked are both Windows 2003 servers and have 2GB and 3GB RAMs respectively. I always thought that specifying the initial heap size with -xms will force java to use at least that much of memory. Am I wrong? Or, is this a peculiarity with java on Windows?

Answer 1

Look closer. The task manager is often misleading - by default it will not show how much memory a process has allocated. Rather what is shown as "memory used" is the amount of physical memory swapped in for that process. In the View menu, chose "Select columns" and add "Size of virtual memory". There's your memory. Your application obviously never really uses more than 500-600m, so its never swapped in.