Re: Permanent Generation and garbage collection

From:

Lew <noone@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 12 Aug 2009 16:41:09 -0400

Message-ID:

<h5v9d6$7b5$1@news.albasani.net>

Patricia Shanahan <pats@acm.org> writes:

I wonder whether it would be possible to use
java.lang.ref.WeakReference and a ReferenceQueue to see whether any of
the ClassLoader and Class objects are being freed?

Tassilo Horn wrote:

For the custom ClassLoader I do count object creations and finalizations
now. And indeed, after I dropped the last reference to some class
loader (at least in my code, dunno if there are references to it in the
JVM internals), the finalize() method isn't called. So I guess, there
are still references to the classes it loaded, or to objects of those
classes.

Finalizers make life worse for GC. Patricia's suggestions will allow you to
monitor that things are released without the overhead of finalize().

For one thing, having a non-trivial finalize() guarantees that a dead object
will need a minimum of two collection cycles to release. If you are using
lots of heap with finalizable objects, the collector might not be able to gain
enough in one collection to avoid OOME.

--
Lew