Chris, Sorry about the long delay, Exchange took a break this morning.
>-----Original Message----- >From: Christopher Schultz [mailto:ch...@christopherschultz.net] >Subject: Re: memory question - heap size and windows process > >Leo, > >On 1/24/2011 10:30 AM, Leo Donahue - PLANDEVX wrote: >> Is there a correlation between the heap size Tomcat is using and the >memory allocated to the Tomcat process running as a windows service - >depicted in task manager, or are these not related to one another? > >Well, one would expect that as heap size increases, so does the total >amount of memory allocated to the process, but I'm guessing you were >hoping for something more helpful :) > >> Tomcat 6.0.29 - windows service - 512MB initial and max memory > >So you are trying to get a fixed heap size: okay. > >> Tomcat as listed in windows task manager: 312,664k > >That seems strange: I would expect the JVM to pre-allocate the entire >heap (512MiB) plus allocate everything else it might need (PermGen, >stack space, native heap, etc.) so you should exceed 512MiB as soon as >the process launches. > >Which number are you observing in the Windows Task Manager? It can show >you a lot of different memory numbers. > Memory Usage, not Memory Usage Delta. >> >> Tomcat as listed in jvisualvm: >> >> Heap >> Size: 518,979,584 B Used: 175,853,040 B >> Max: 518,979,584 B > >That looks right. > >> PermGen >> Size: 33,816,576 B Used: 33,771,424 B >> Max: 67,108,864 B > >Okay, so you have 512MiB of Java heap and 30MiB of PermGen so your >process should take at minimum 542MiB of space. I'd be shocked if you >had less than a 300MiB virtual size, though the memory might not >actually be used at this point, so Microsoft Windows might not report >it. > >I don't know much about Microsoft Windows, but I know that Linux doesn't >even allocate memory to you until you actually write to it, so the >actual amount of memory allocated to a JVM can be quite modest compared >to the amount you expected to use upon JVM launch. Perhaps Microsoft >Windows does something similar... though that would have to be a >relatively new improvement (Vista/7?). > Using Windows Server 2003 Standard R2 > >Were you hoping to get an answer to a specific question? > Yes, but asking the right question is the hardest part.
