You might want to look at the VM performance numbers in my Performance article. The link is listed on the tomcat resources page. Generally, tweaking the generations takes time. for something, like XML, tweaking generation ratio doesn't help. peter
Michael Duffy <[EMAIL PROTECTED]> wrote: Hi Yoav, > 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. I've never checked this page out before, but at your prompting I found it today: http://java.sun.com/docs/hotspot/VMOptions.html I believe the docs are telling me that the default value of XX:NewRatio=12 for Intel. Is that correct? If that's true, should I just leave the default? I have no experience with setting any of these values. I've always used the JVM right out of the box (my ignorance). What would be a minimum set of parameters to span this space? Thanks - % --- "Shapira, Yoav" wrote: > > 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] > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------- Do you Yahoo!? Friends. Fun. Try the all-new Yahoo! Messenger
