thanks, by the way, the permanent generation is also collected by major gc? and what will trigger a gc in the permanent generation best regards
2010/11/24 Caldarale, Charles R <chuck.caldar...@unisys.com> > > From: xu cheng [mailto:xcheng....@gmail.com] > > Subject: the memory puzzle me.... > > > I oberved the heap of the jvm which runs tomcat without deploying > > any webapp. and it's some kind like this /|/|/|/|/|/| > > That's called a sawtooth pattern, and is what you should be seeing. > > > when the used heap goes up, there is a memory use of the heap, > > maybe allocation for the new class instances, and when it goes > > down , there is a gc, am I right? > > Yes; the GC you're seeing is very likely what's called a "minor GC", which > cleans out only the young generation, which is where nearly all objects are > created and the vast majority die. A major GC will process not only the > young generation, but also the tenured (old) and so-called permanent ones. > (Note that most things in the perm gen space are not actually permanent, > and not necessarily even long-lived.) > > > but I didn't deploy any app on the tomcat. I'm just wondering > > what is using the memory? > > Tomcat has numerous background threads doing such things as waiting for > connections from clients, checking for webapp deployments, monitoring > changes to deployed webapps, etc. All of these are creating a few objects > for very short periods, over and over. > > - 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 > >
