Hi, I downloaded this and it seems to have potential. Unfortunately I cant work out where to get the heap sizing information which is one of the more important things to us. Anyway used it and can point me in the right direction.
Ta Matt -----Original Message----- From: Peter Lin [mailto:[EMAIL PROTECTED] Sent: 10 June 2004 03:15 To: Tomcat Users List Subject: RE: Memory Settings On Tomcat 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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