Hi, >I've got Tomcat 4.1.29 installed to run as a service >under JDK 1.4.1_05 on this Windows 2000 server. The >Tomcat memory settings on startup are -Xms64m and >-Xmx1024m. The server has 512MB of physical RAM
It's not a good idea to set -Xmx to a higher amount than the amount of physical RAM: the JVM will thrash once it reaches much less than 512MB. >My understanding is that Java's garbage collection >will reclaim heap-allocated memory to the JVM, but not >necessarily to the OS. Is this true? What this means >is that a Windoze server admin could look at the task >manager and see a large memory usage for Tomcat, but >that doesn't necessarily reflect Tomcat's current >usage. > >It's more like a high water mark on a pier: it'll show >the highest value that Tomcat has used, but the real >value will be lower if the garbage collector runs and >the tide goes out. If you read a lot of objects into >session you could end up with a big high water mark. Your understanding is good and correct on the above issues. >(1) Is my understanding of the interaction between the >JVM and OS memory management correct? >(2) Are there any other tuning settings for Tomcat >that I need to look at? Yes to 1, and likely yes to 2. Check out the different garbage collector implementations, and the directives for setting old and young generation sizes. Your case is a classic one for setting a small old generation size relative to the young generation size: maybe even a 10-1 or slightly less ratio of young size to old size. And there's the ever-present (which is why it's often forgotten) advice: you might want to get more physical RAM. It's pretty cheap, and 512MB isn't that much for a server nowadays. Yoav This e-mail, including any attachments, is a confidential business communication, and may contain information that is confidential, proprietary and/or privileged. This e-mail is intended only for the individual(s) to whom it is addressed, and may not be saved, copied, printed, disclosed or used by anyone else. If you are not the(an) intended recipient, please immediately delete this e-mail from your computer system and notify the sender. Thank you. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
