> From: Christopher Schultz [mailto:ch...@christopherschultz.net] > Subject: Re: tomcat memory question > > Check may (will?) correct me on this
-1 for spelling > I believe a full GC might be necessary to clear-out certain > resources such as completed Threads or other things that have > concrete OS-level counterparts. Not exactly; a full GC is necessary to clear out dead classes and any objects that have migrated into the tenured generation. The OS-level thread structures are gone as soon as the java.lang.Thread instance stops running (returns from the run() method), while the Java instance will hang around as long as there are references to it. Some OS resources will stay allocated until a GC happens *if* the program fails to explicitly close them before the corresponding Java object becomes unreachable (aka sloppy programming), but any kind of GC that discovers such a dead object will release the associated native resources. > If you are using a lot of (non-pooled) threads or socket > connections, the JVM may be performing full GCs to clean > up those resources. GC itself knows nothing about the relationship between Java objects and external resources; only the finalizer for such a class does. > Frequent full GCs might just mean that you are using a lot of your > memory. As long as you don't get any OutOfMemoryErrors, it appears > that your heap is adequate for the load you're experiencing. Assuming there are no memory leaks, it's an indication that the heap is undersized for the application, or that the application is behaving in an unexpected fashion with regard to expected object creation patterns. (An application that creates only long-lived objects, for example - but that's really hard to believe that could happen in a servlet container.) - 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.
