Re: [aus-dotnet] A Comparison of .NET and Java GC

[Joseph Cooney]

Re: GC and resource management.... A pedantic person would say that
Garbage Collection is just management of one particular kind of
resource (memory), and that the interaction between garbage collection
and management of other types of resources (database connections, file
handles etc) is often of interest to programmers so the two are not
unrelated.

On Wed, 7 Jul 2004 10:34:53 +0930 , Nick Lothian <nl@xxxxxxxxxxxxxxxx> wrote:
> 
> >
> > ".NET GC is Excellent - Better Than Java" -
> > http://weblogs.asp.net/pwilson/archive/2004/02/20/77448.aspx
> >
> > Ok, first 4 probably not exactly what you're after, but the
> > last one is an
> > interesting read. First 4 may give those asking about the GC
> > a bit more info
> > on it.
> 
> I don't know much about the .NET GC, but I do know the Java GC enough to
> know that this guy is confusing garbage collection and resource management.
> I guess that's a common enough confusion, but it isn't good to see it put
> around as a fact.
> 
> He says:
> 
> "As for the Dispose method, I learned that this pattern is commonly used and
> accepted as necessary in Java, but it was never officially made part of Java
> itself, which is one place .NET is actually better since they learned from
> Java's experience."
> 
> To a certain extend this is true - is you have a resource in Java that you
> need to clean up after user you need to use try {...} finally {} blocks.
> IDisposable is a nice piece of syntactic sugar that makes that a bit
> cleaner. A nice summary of this is at
> http://www.neward.net/ted/weblog/index.jsp?date=20040123
> 
> However, that has NOTHING to do with garbage collection - in fact it is the
> opposite. IDisposable or try {..} finally {} let you clean up resources that
> garbage collection do not manage (typical examples are things like managing
> pooled connections to something where you want to keep the connection
> objects, but close the network connection).
> 
> Back to Garbage Collection:
> 
> A good overview of the .NET GC is
> <http://msdn.microsoft.com/msdnmag/issues/1100/GCI/default.aspx> and
> <http://msdn.microsoft.com/msdnmag/issues/1200/GCI2/default.aspx>
> 
> There is probably more documentation available on Java GC, simply because it
> has been around longer and gone through more revisions. Start with
> http://java.sun.com/docs/hotspot/gc/index.html and
> http://java.sun.com/docs/hotspot/gc1.4.2/faq.html
> 
> I wrote a blog entry on tuning the Java GC with the Java Jvmstat tool, which
> includes some more links:
> <http://www.mackmo.com/nick/blog/java/?permalink=jvmstat.txt>. Note that the
> Java 1.5 VM (or Java 5 VM as it is now know) does more goal orientated self
> tuning of its GC algorithm (they call it garbage collector ergonomics). I
> haven't looked at this in a great deal of detail, but I'd consider it a good
> thing since GC tuning is currently something of a black art. See
> http://java.sun.com/j2se/1.5.0/docs/guide/vm/gc-ergonomics.html
> 
> If you are really interested in garbage collection I highly recommend
> running jvmstat against a Java program. It is quite amazing to see the
> generational GC working - you watch as objects get copied from the Eden
> space to the survivor pools, and then on to the old and permanent
> generations. You can see the difference the various GC algorithms make, too.
> 
> Nick
> 
> Nick
> 
> 
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