Enclosed is a spreadsheet (Excel 5.0) showing the memory problems when we
run the Classic Blend applet in Java Plugin 1.1 (JRE 1.1.6). When we run
the same applet in Internet Explorer's native Java VM, there are no memory
problems. The problem is very repeatable (ie happens every time) when
running the whole applet.

As I mentioned on the phone, we have written two large applications in
SmallTalk using Visual Works from ObjectShare. The Visual Works server
runs on a Sun Enterprise 3000 in our beta/preprod environment and an
Enterprise 4000 in production. In the Visual Works server image is the
Classic Blend product from Applied Reasoning. Classic Blend "scrapes" the
screen drawing commands off the Visual Works server and pipes them to their
Java applet that runs in Java Plugin 1.1's JRE. The Classic Blend product
uses a table drawing widget called JKIT from Instantiations Corp. which
uses AWT to draw tables. The table drawing appears to be the worst
offender in terms of eating up memory. In the spreadsheet you will find a
couple of rows where total memory allocated goes up by 5+ MBs with Java
Plugin and 0 MBs with IE's native VM. Those rows are where JKIT is drawing
tables.

I have created a testcase using the JKit example classes. Unfortunately,
I was not able to create a testcase without using the JKit classes, so
they are included. Fortunately, I was able to determine a starting point
that seems to be causing the problem. Hopefully the sun engineers can
checkpoint this message to watch the execution and determine the memory
usage.

The testcase is a simple Java applet that contains buttons that launch
various JKit examples.

The class and java files are included in the test.jar file. The html
files are included in html.zip.

I ran this test on Win NT4.0 SP3, 128MB memory. I used the FNord web
server to serve up the html and jar files.

Here is the case:

Start the NT Task Manager. Select the Performance tab. What we are
concerned with is the MEM Usage value. This indicates the total memory
used by the system. You will NOT see the memory usage by watching the
IEXPLORER process on the Processes tab.

Start IE4.0. Type in the URL for the testPI.html file (e.g.
http://yourwebserver/testPI.html ). This will start the Plug in.

The Java console should appear and display something like:


     Java(TM) Plug-in
     Using JRE version 1.1.6
     User home directory = C:\WINNT\Profiles\cnormand
     Proxy Configuration: Manual Configuration
          Proxy:
     http=208.206.247.233:8011;https=208.206.247.233:8011;ftp=208.206.247.233:8011

          Proxy Overrides:

     JAR cache enabled.
     Opening http://naomi/jkit/test.jar proxy=208.206.247.233:8011

The applet will contain some buttons. Press the button labeled LRC
(which stands for Large Rows and Columns). Something like the following
will appear in the Java Console:


     Button pressed: LRC
     About to init Applet
     Initializing Table
     Done Initializing
     Adding component
     test.VarSimple[panel3,0,0,0x0,invalid,layout=java.awt.BorderLayout]
     -> Center
     Resizing to: 400, 400
     Showing...
     Resizing to: 400, 398
     Validating...Thread[AWT-EventQueue-0,5,main] validatedOnce =
     false
     DONE Validating Thread[AWT-EventQueue-0,5,main]
     Orig total=4444152 free=1213864 Now total=6037496 free=1407840
     Memory used (negative means memory returned): 1399368
     Validating...Thread[AWT-EventQueue-0,5,main] validatedOnce =
     false
     DONE Validating Thread[AWT-EventQueue-0,5,main]
     Validating...Thread[AWT-EventQueue-0,5,main] validatedOnce =
     true
     Waiting 30 seconds...

At which point you will see a partially drawn window on the screen.
During the 30 second wait, record the total memory usage on the task
manager. Once the 30 second wait has completed, the following will
appear:


     Wait done. Performing second validation... Watch the total
     memory grow
     DONE Validating Thread[AWT-EventQueue-0,5,main]
     Resizing to: 400, 379

The window should be completely drawn and appear with a table widget and
a few buttons. Now examine the total memory usage from the task
manager. In most cases, my memory usage jumped 8 MB.

The method in question is TestExampleFrame.invalidate(). It is being
called 3 times (not normally a problem). The first two invokations
appear to be in the same call stack, since the 'validatedOnce' variable
is still false in the second invokation. The third invokation, however,
occurs in a separate call stack, since the 'validatedOnce' variable is
true. The method looks like:


     public void validate() {
          System.out.print("Validating..." +
     Thread.currentThread());
          System.out.println(" validatedOnce = " + validatedOnce);
          if (validatedOnce) {
               System.out.println("Waiting 30 seconds...");
               try { Thread.sleep(30000); } catch
     (InterruptedException ie) {}
               System.out.println("Wait done. Performing second
     validation... Watch the total memory grow");
          }
          super.validate();
          validatedOnce = true;
          System.out.println("DONE Validating " +
     Thread.currentThread());
     }

The memory increase occurs during the 3rd invokation of the validate
method.

The drastic memory increase does NOT appear when running this testcase in
IE4.0, without the Plug in (execute the html file 'test.html' instead of
'testPI.html' and follow the same steps).

An interesting point: when running in IE4.0 without the Plug in, the
validation method is only called twice. The window is completely drawn
after the 2nd invalidate.