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JDK-6717198 : Cache: JVM very slow to load applets when disk cache is not empty

Details
Type:
Enhancement
Submit Date:
2008-06-20
Status:
Open
Updated Date:
2014-09-04
Project Name:
JDK
Resolved Date:
Component:
deploy
OS:
windows_xp
Sub-Component:
deployment_toolkit
CPU:
x86
Priority:
P2
Resolution:
Unresolved
Affected Versions:
6u10
Targeted Versions:
8u40

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Sub Tasks

Description
FULL PRODUCT VERSION :
java.runtime.version = 1.6.0_10-beta-b25

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
I develop applets.  All day long I make changes.  Each change requires me to rebuild the jar(s) and then go to the Java console and type "X" to clear the cache.  I then reload the applet to test my changes.

The longer I do this, the longer it takes for the initial load of the applet.

If I close the browser completely, and clear all temporary Internet Files via the Java control panel application (Start->Control Panel->Java->General tab->Temporary Internet Files->Settings...->Delete Files...->OK to Applications and Applets and Trace and Log Files), then restart my browser and start testing my applets again, they load super fast.  As stated previously, the longer I test, the slower the applet loads.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1) Create a jar with an applet.
2) Create a jsp file that references the applet and place on a web server.
3) Load the jsp using Internet Explorer.
4) Rebuild the applet jar file.
5) Open the plug-in console and type "X" to clear cache.
6) Reload the applet by clicking refresh in browser.
7) Repeat steps 4-7.  After 20 or 30 iterations, you will notice that step 6 takes a long time.
8) That's it.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Applets should load at the same speed regardless of local disk caching.
ACTUAL -
After clearing the cache in the plug-in console and reloading the same applet about 30 times, the applet loads very slowly.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.Graphics;
import java.util.Stack;
import java.util.Vector;
import java.awt.event.*;

/**  java demo code for CLSFractal.java from
* http://java.sun.com/applets/jdk/1.4/demo/applets/Fractal/example1.html
 * A (not-yet) Context sensitive L-System Fractal applet class.
 *
 * The rules for the Context L-system are read from the java.applet.Applet's
 * attributes and then the system is iteratively applied for the
 * given number of levels, possibly drawing each generation as it
 * is generated.  Note that the ContextLSystem class does not yet
 * handle the lContext and rContext attributes, although this
 * class is already designed to parse the '[' and ']' characters
 * typically used in Context sensitive L-Systems.
 *
 * @author 	Jim Graham
 * @version 	1.1f, 27 Mar 1995
 */
public class CLSFractal
    extends java.applet.Applet
    implements Runnable, MouseListener {
    Thread kicker;
    ContextLSystem cls;
    int fractLevel = 1;
    int repaintDelay = 50;
    boolean incrementalUpdates;
    float startAngle = 0;
    float rotAngle = 45;
    float Xmin;
    float Xmax;
    float Ymin;
    float Ymax;
    int border;
    boolean normalizescaling;

    public void init() {
	String s;
	cls = new ContextLSystem(this);
	s = getParameter("level");
	if (s != null) fractLevel = Integer.parseInt(s);
	s = getParameter("incremental");
	if (s != null) incrementalUpdates = s.equalsIgnoreCase("true");
	s = getParameter("delay");
	if (s != null) repaintDelay = Integer.parseInt(s);
	s = getParameter("startAngle");
	if (s != null) startAngle = Float.valueOf(s).floatValue();
	s = getParameter("rotAngle");
	if (s != null) rotAngle = Float.valueOf(s).floatValue();
	rotAngle = rotAngle / 360 * 2 * 3.14159265358f;
	s = getParameter("border");
	if (s != null) border = Integer.parseInt(s);
	s = getParameter("normalizescale");
	if (s != null) normalizescaling = s.equalsIgnoreCase("true");
	addMouseListener(this);
    }

    public void destroy() {
        removeMouseListener(this);
    }

    public void run() {
	Thread me = Thread.currentThread();
	boolean needsRepaint = false;
	while (kicker == me && cls.getLevel() < fractLevel) {
	    cls.generate();
	    if (kicker == me && incrementalUpdates) {
		repaint();
		try {Thread.sleep(repaintDelay);} catch (InterruptedException e){}
	    } else {
		needsRepaint = true;
	    }
	}
	if (kicker == me) {
	    kicker = null;
	    if (needsRepaint) {
		repaint();
	    }
	}
    }

    public void start() {
	kicker = new Thread(this);
	kicker.start();
    }

    public void stop() {
	kicker = null;
    }

      /*1.1 event handling */
    public void mouseClicked(MouseEvent e) {
    }

    public void mousePressed(MouseEvent e) {
    }

    public void mouseReleased(MouseEvent e) {
        cls = new ContextLSystem(this);
        savedPath = null;
        start();
        e.consume();
    }

    public void mouseEntered(MouseEvent e) {
    }

    public void mouseExited(MouseEvent e) {
    }

    String savedPath;

    public void paint(Graphics g) {
	String fractalPath = cls.getPath();
	if (fractalPath == null) {
	    super.paint(g);
	    return;
	}
	if (savedPath == null || !savedPath.equals(fractalPath)) {
	    savedPath = fractalPath;
	    render(null, fractalPath);
	}

	for (int i = 0; i < border; i++) {
	    g.draw3DRect(i, i, getSize().width - i * 2, getSize().height - i * 2,false);
	}
	render(g, fractalPath);
    }

    void render(Graphics g, String path) {
	Stack turtleStack = new Stack();
	CLSTurtle turtle;

	if (g == null) {
	    Xmin = 1E20f;
	    Ymin = 1E20f;
	    Xmax = -1E20f;
	    Ymax = -1E20f;
	    turtle = new CLSTurtle(startAngle, 0, 0, 0, 0, 1, 1);
	} else {
	    float frwidth = Xmax - Xmin;
	    if (frwidth == 0)
		frwidth = 1;
	    float frheight = Ymax - Ymin;
	    if (frheight == 0)
		frheight = 1;
	    float xscale = (getSize().width - border * 2 - 1) / frwidth;
	    float yscale = (getSize().height - border * 2 - 1) / frheight;
	    int xoff = border;
	    int yoff = border;
	    if (normalizescaling) {
		if (xscale < yscale) {
		    yoff += ((getSize().height - border * 2)
			     - ((Ymax - Ymin) * xscale)) / 2;
		    yscale = xscale;
		} else if (yscale < xscale) {
		    xoff += ((getSize().width - border * 2)
			     - ((Xmax - Xmin) * yscale)) / 2;
		    xscale = yscale;
		}
	    }
	    turtle = new CLSTurtle(startAngle, 0 - Xmin, 0 - Ymin,
				   xoff, yoff, xscale, yscale);
	}

	for (int pos = 0; pos < path.length(); pos++) {
	    switch (path.charAt(pos)) {
	    case '+':
		turtle.rotate(rotAngle);
		break;
	    case '-':
		turtle.rotate(-rotAngle);
		break;
	    case '[':
		turtleStack.push(turtle);
		turtle = new CLSTurtle(turtle);
		break;
	    case ']':
		turtle = (CLSTurtle) turtleStack.pop();
		break;
	    case 'f':
		turtle.jump();
		break;
	    case 'F':
		if (g == null) {
		    includePt(turtle.X, turtle.Y);
		    turtle.jump();
		    includePt(turtle.X, turtle.Y);
		} else {
		    turtle.draw(g);
		}
		break;
	    default:
		break;
	    }
	}
    }

    void includePt(float x, float y) {
	if (x < Xmin)
	    Xmin = x;
	if (x > Xmax)
	    Xmax = x;
	if (y < Ymin)
	    Ymin = y;
	if (y > Ymax)
	    Ymax = y;
    }

  public String getAppletInfo() {
    return "Title: CLSFractal 1.1f, 27 Mar 1995 \nAuthor: Jim Graham \nA (not yet) Context Sensitive L-System production rule. \nThis class encapsulates a production rule for a Context Sensitive\n L-System \n(pred, succ, lContext, rContext).  The matches() method, however, does not \n(yet) verify the lContext and rContext parts of the rule.";
  }

  public String[][] getParameterInfo() {
    String[][] info = {
      {"level", "int", "Maximum number of recursions.  Default is 1."},
      {"incremental","boolean","Whether or not to repaint between recursions.  Default is true."},
      {"delay","integer","Sets delay between repaints.  Default is 50."},
      {"startAngle","float","Sets the starting angle.  Default is 0."},
      {"rotAngle","float","Sets the rotation angle.  Default is 45."},
      {"border","integer","Width of border.  Default is 2."},
      {"normalizeScale","boolean","Whether or not to normalize the scaling.  Default is true."},
      {"pred","String","Initializes the rules for Context Sensitive L-Systems."},
      {"succ","String","Initializes the rules for Context Sensitive L-Systems."},
      {"lContext","String","Initializes the rules for Context Sensitive L-Systems."},
      {"rContext","String","Initializes the rules for Context Sensitive L-Systems."}
    };
    return info;
  }
}

/**
 * A Logo turtle class designed to support Context sensitive L-Systems.
 *
 * This turtle performs a few basic maneuvers needed to support the
 * set of characters used in Context sensitive L-Systems "+-fF[]".
 *
 * @author 	Jim Graham
 * @version 	1.1f, 27 Mar 1995
 */
class CLSTurtle {
    float angle;
    float X;
    float Y;
    float scaleX;
    float scaleY;
    int xoff;
    int yoff;

    public CLSTurtle(float ang, float x, float y,
		     int xorg, int yorg, float sx, float sy) {
	angle = ang;
	scaleX = sx;
	scaleY = sy;
	X = x * sx;
	Y = y * sy;
	xoff = xorg;
	yoff = yorg;
    }

    public CLSTurtle(CLSTurtle turtle) {
	angle = turtle.angle;
	X = turtle.X;
	Y = turtle.Y;
	scaleX = turtle.scaleX;
	scaleY = turtle.scaleY;
	xoff = turtle.xoff;
	yoff = turtle.yoff;
    }

    public void rotate(float theta) {
	angle += theta;
    }

    public void jump() {
	X += (float) Math.cos(angle) * scaleX;
	Y += (float) Math.sin(angle) * scaleY;
    }

    public void draw(Graphics g) {
	float x = X + (float) Math.cos(angle) * scaleX;
	float y = Y + (float) Math.sin(angle) * scaleY;
	g.drawLine((int) X + xoff, (int) Y + yoff,
		   (int) x + xoff, (int) y + yoff);
	X = x;
	Y = y;
    }
}

/**
 * A (non-)Context sensitive L-System class.
 *
 * This class initializes the rules for Context sensitive L-Systems
 * (pred, succ, lContext, rContext) from the given java.applet.Applet's attributes.
 * The generate() method, however, does not (yet) apply the lContext
 * and rContext parts of the rules.
 *
 * @author 	Jim Graham
 * @version 	1.1f, 27 Mar 1995
 */
class ContextLSystem {
    String axiom;
    Vector rules = new Vector();
    int level;

    public ContextLSystem(java.applet.Applet app) {
	axiom = app.getParameter("axiom");
	int num = 1;
	while (true) {
	    String pred = app.getParameter("pred"+num);
	    String succ = app.getParameter("succ"+num);
	    if (pred == null || succ == null) {
		break;
	    }
	    rules.addElement(new CLSRule(pred, succ,
					 app.getParameter("lContext"+num),
					 app.getParameter("rContext"+num)));
	    num++;
	}
	currentPath = new StringBuffer(axiom);
	level = 0;
    }

    public int getLevel() {
	return level;
    }

    StringBuffer currentPath;

    public synchronized String getPath() {
	return ((currentPath == null) ? null : currentPath.toString());
    }

    private synchronized void setPath(StringBuffer path) {
	currentPath = path;
	level++;
    }

    public void generate() {
	StringBuffer newPath = new StringBuffer();
	int pos = 0;
	while (pos < currentPath.length()) {
	    CLSRule rule = findRule(pos);
	    if (rule == null) {
		newPath.append(currentPath.charAt(pos));
		pos++;
	    } else {
		newPath.append(rule.succ);
		pos += rule.pred.length();
	    }
	}
	setPath(newPath);
    }

    public CLSRule findRule(int pos) {
	for (int i = 0; i < rules.size(); i++) {
	    CLSRule rule = (CLSRule) rules.elementAt(i);
	    if (rule.matches(currentPath, pos)) {
		return rule;
	    }
	}
	return null;
    }
}

/**
 * A Context sensitive L-System production rule.
 *
 * This class encapsulates a production rule for a Context sensitive
 * L-System (pred, succ, lContext, rContext).
 * The matches() method, however, does not (yet) verify the lContext
 * and rContext parts of the rule.
 *
 * @author 	Jim Graham
 * @version 	1.1f, 27 Mar 1995
 */
class CLSRule {
    String pred;
    String succ;
    String lContext;
    String rContext;

    public CLSRule(String p, String d, String l, String r) {
	pred = p;
	succ = d;
	lContext = l;
	rContext = r;
    }

    public boolean matches(StringBuffer sb, int pos) {
	if (pos + pred.length() > sb.length()) {
	    return false;
	}
	char cb[] = new char[pred.length()];
	sb.getChars(pos, pos + pred.length(), cb, 0);
	return pred.equals(new String(cb));
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Close the browser completely, and clear all temporary Internet Files via the Java control panel application (Start->Control Panel->Java->General tab->Temporary Internet Files->Settings...->Delete Files...->OK to Applications and Applets and Trace and Log Files), then restart browser.

                                    

Comments
EVALUATION

this should be addressed by the new plugin in 6u10, with the new option to disable classloader cache:

http://java.sun.com/javase/6/webnotes/6u10/plugin2/index.html#CLASS_LOADER_CACHING
                                     
2008-11-19



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