Description Samantha Chan 2008-06-03 15:47:53 EDT

1.  Our products have many logical structures.
2.  When debugging a large application, like a web server, or another instance of Eclipse, etc, we find that expanding a variable from the variables view is extremely slow if both logical structures and show references are turned on in the Variables View.

Here's some timing information when show references is turned on:

            Logical Structures On            Logical Structures Off
Dual Core   ~ 25 seconds                     ~ 1.5 seconds
Single CPU  ~ 45 seconds                     ?
Slow Linux  ~ 8 minutes                      3 seconds


When logical structures are turned on, I see that there are a bunch of JdwpCommandPacket.VM_CLASSES_BY_SIGNATURErequest sent, and they seem be time consuming.

Doing a little more digging, I see these requests are a result of each of the logical structure type delegates having their providesLogicalStructure(IValue value) method being called. They all seem to call IJavaobject.getJavaType(), which results in the JdwpCommandPacket.VM_CLASSES_BY_SIGNATURErequest.

I see that the IJavaObject is really a JDIReferenceListValue.  The getJavaType() method of JDIReferenceListValue does not cache its value, so for every logical structure type delegate, this same JDIReferenceListValue.getJavaType() call results in a JdwpCommandPacket.VM_CLASSES_BY_SIGNATURErequest.

I added caching to the JDIReferenceListValue.getJavaType() method, and the expansion time for the references node dropped to ~1.5 seconds, which is the same as when logical structures is not turned on.

Is there some reason that the getJavaType() method should not be caching the result?
If not, would it be possible to get this change into Eclipse 3.4?

This is my caching version of JDIReferenceListValue.getJavaType() :
	public IJavaType getJavaType() throws DebugException {
		if (fJavaType == null) {
			IJavaType[] javaTypes = getJavaDebugTarget().getJavaTypes(getReferenceTypeName());
			if (javaTypes.length > 0) {
		//		return javaTypes[0];
				fJavaType = javaTypes[0];
			}
		}
	//	return null;
		return fJavaType; 
	}

Here's some timing information when this fix is applied:
            Logical Structures On  
Dual Core   1.5 seconds
Single CPU  3 seconds
Slow Linux  4 seconds

We can try to optimize our code in our logical structures delegate.  Our experiments show that we can only reduce the time to expand variables by half.  We were not able to reduce it down to the "seconds" range.