by the way, in case you haven't heard of it, http://mc4j.sourceforge.net/
mc4J can monitor tomcat4 and generate nice graphs. I haven't used it, but it looks nice. peter --- Michael Duffy <[EMAIL PROTECTED]> wrote: > > Hi Peter, > > Hiding in plain sight: > > http://jakarta.apache.org/tomcat/articles/performance.pdf > > I apologize for overlooking it for all this time. > I'll be sure to go through it right away. Thanks - > % > > > --- Peter Lin <[EMAIL PROTECTED]> wrote: > > > > 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. 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