> 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
