Default MessageReceiver

[Bartek]

I took a look at how Controller instantiates a MessageReceiver. I analyzed
9.1.0.8 source code, but it seems that the impl in the latest ver is similar.
I think that in a situation when classname is not overridden (the default one
is used), it'd be more optimal to just instantiate it directly and not load
the class each time a new instance is needed. Just call new
net.sf.saxon.serialize.MessageEmitter().

With the current impl threads wait on ClassLoader.loadClass() which is
synchronized.

Bartek

[Michael Kay]

Do you have evidence that this change would make a measurable performance
difference?

[Bartek]

Hi,

We haven't done any comparative performance tests. I can only say that we did
tests with ~160 tps, with 3 transformations for each message. When doing
thread dumps, we observed plenty of threads waiting on synchronization on
ClassLoader.loadClass() caused by loading the emitter/receiver class.

Thanks,
Bartek

[Michael Kay]

Saxon doesn't in fact go to the ClassLoader to load this class each time,
because it's one of the classes that is known to the DynamicLoader in package
net.sf.saxon.trans. It does do a reflexive instantiation of the class using
getInstance(), but I'd be surprised if doing that once per transformation is
really a measurable overhead.

So I don't understand why you should observe threads waiting on
ClassLoader.loadClass() with this class unless you customized something.

[Michael Kay]

So I don't understand why you should observe threads waiting on
ClassLoader.loadClass() with this class unless you customized something.

Or you would see it on 9.1, which doesn't have this optimization.

[Bartek]

Hi,

Yup, I'm using 9.1.0.8. I've just checked 9.3.0.4 sources and you're right.
It's no longer a problem:

protected void registerKnownClasses() {
knownClasses.put("net.sf.saxon.serialize.MessageEmitter",
MessageEmitter.class);
//knownClasses.put("net.sf.saxon.java.JavaPlatform", JavaPlatform.class); //
not available on .NET
knownClasses.put("net.sf.saxon.Configuration", Configuration.class);
}

Thanks,
Bartek