On Fri, 2011-12-09 at 06:52 -0800, Martin O'Shea wrote: > Thanks for this Chuck. I realise now what is happening. I thought the > PermGen space was used in the heap when now I see it as just storing class > definitions. So I could reduce it below 128Mb if I choose. Is there a > default value?
This is a useful article which describes many of the common JVM options and their defaults. http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html It lists "-XX:MaxPermSize" as a default of 64M with the following exceptions: "[5.0 and newer: 64 bit VMs are scaled 30% larger; 1.4 amd64: 96m; 1.3.1 -client: 32m.]". If I connect to a Java process on my Linux system with a 64-bit JVM, I see a max of roughly 64M + 30% (i.e. about 83M). Dan > > As to setting Xms and Xmx to the same, I will do that. A job hung earlier > and I wonder if memory was to blame although there is nothing in the system > or server logs to say so. > > -----Original Message----- > From: Caldarale, Charles R [mailto:chuck.caldar...@unisys.com] > Sent: 09 Dec 2011 14 46 > To: Tomcat Users List > Subject: RE: Tomcat memory allocation > > > From: Martin O'Shea [mailto:app...@dsl.pipex.com] > > Subject: Tomcat memory allocation > > > Following advice found elsewhere on the internet > > Always to be taken with large chunks of salt. > > > set JAVA_OPTS=%JAVA_OPTS% -Xms128m -Xmx512m -XX:MaxPermSize=128m > > You would be better off using CATALINA_OPTS, since setting JAVA_OPTS > pointlessly affects the shutdown script as well as the startup one. > > > I know that settings: > > Xms128m -Xmx512m > > > Control the initial heap size and what it can expand to. > > In a server environment, you normally want Xms and Xmx set to the same value > to avoid heap thrashing. The exact size is completely dependent on what > your webapps need. > > > But what exactly is: > > -XX:MaxPermSize=128m > > It's the amount of space to which the so-called permanent generation can > expand. PermGen holds primarily instances of java.lang.Class, so it only > needs to be specified if you have a large number of classes in your > environment. > > > Should it be set to an addition of the other settings, or the other > > settings to an addition of it? > > What does that question mean? PermGen size is completely independent of the > heap size. > > Make sure you have enough RAM available on the system to support the Xmx + > PermGen + a_lot_of_other_stuff. Monitor the system to make sure you're not > getting into paging. > > - Chuck > > > THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY > MATERIAL and is thus for use only by the intended recipient. If you received > this in error, please contact the sender and delete the e-mail and its > attachments from all computers. > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org >
