RE: HOW TO: How do I allocate memory in JVM for extra virtual hos ts

["Takaoglu, Uzay" <ut...@syscom.com>]

 There are several things you can do (on 1.3.1 and after):

 1. Make sure your global and local class parms are explicitly set to null
after the work is being completed
 2. Heavily used classes should provide their own finalize methods
 3. You will need to call JVM to run finalization and recommend JVM to run
the GC. (System.runFinalization() and System.gc() ). However, be very
careful with these methods since specially System.runFinalization() might
clean up the objects that you still need. 
 4. Use -server option for HotSpot since it's GC is much better than regular
GC
 5. If all above does not work, then try using java.lang.ref.Reference
package to explicitly define your reference types so they would easily be
collected by the GC (weak references, unreachable object etc.)
 6. do NOT set Xmx and Xms to "same" value
 7. Look at -XX options of the JVM and do more reading abouts eden, young,
old generations. Some options are XX:SurvivorRatio and
XX:SoftRefLRUPolicyMSPerMB 

-----Original Message-----
From: Donie Kelly
To: 'Tomcat Users List'
Sent: 9/27/02 6:12 AM
Subject: HOW TO: How do I allocate memory in JVM for extra virtual hosts

Hi all
I am running tomcat 4.0.1 with virtual hosting and was wondering how
much
memory to allocate to each additional host. By default, we use 64M for
one
host but adding another 64M for second host seems excessive considering
it's
the same tomcat instance.
However, if we add a lot the JVM will use more memory before garbage
collection and we've seen a 30 second (!!!) delay when using 1G Ram on
JVM
as it just kept using memory until it ran out. It then had almost 1G of
ram
to garbage collect. How can I force garbage collection to be more
aggressive
and do it more often when garbage is small enough not to cause a
problem?
As we need this to run in a production environment we cannot possible
allow
a JVM to go for a garbage break for 30 seconds!!!!
Any insight or help is greatly appreciated.
Donie


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