Disable recordCreateAt from RemoteClassLoader

[jglick]

While trying to diagnose poor performance of a plugin which did heavy remote class loading in a dev build, I saw agent thread dumps such as

"pool-…-thread-… for channel id=… / waiting for channel id=…" … RUNNABLE
	at java.lang.Throwable.getStackTraceElement(Native Method)
	at java.lang.Throwable.getOurStackTrace(Throwable.java:827)
	-  locked hudson.remoting.Command$Source@…
	at java.lang.Throwable.writeObject(Throwable.java:979)
	-  locked hudson.remoting.Command$Source@…
	at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1128)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
	at hudson.remoting.Command.writeTo(Command.java:106)
	at hudson.remoting.AbstractSynchronousByteArrayCommandTransport.write(AbstractSynchronousByteArrayCommandTransport.java:46)
	at hudson.remoting.Channel.send(Channel.java:719)
	-  locked hudson.remoting.Channel@…
	at hudson.remoting.Request.call(Request.java:155)
	-  locked hudson.remoting.RemoteInvocationHandler$RPCRequest@…
	-  locked hudson.remoting.Channel@…
	at hudson.remoting.RemoteInvocationHandler.invoke(RemoteInvocationHandler.java:281)
	at com.sun.proxy.$Proxy5.fetch3(Unknown Source)
	at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:209)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	-  locked hudson.remoting.RemoteClassLoader@…
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at …

While it might theoretically be interesting to diagnose where these commands are being created from, there are a lot of these little calls, and the overhead of constructing a stack trace and passing it through the channel each time seems excessive.

@reviewbybees

[jglick]

Using jenkinsci/support-core-plugin#128, before:

• Writes: 2116
  • sent 5.3Mb
• Reads: 3977
  • received 16.6Mb
• Unexport: 1942
  • received 8.2Mb
• RPCRequest:hudson.remoting.RemoteClassLoader$IClassLoader.fetch3[java.lang.String]: 1948
  • received 7.9Mb

After:

• Writes: 2092
  • sent 5.1Mb
• Reads: 3972
  • received 4.4Mb
• Unexport: 1940
  • received 2.9Mb
• RPCRequest:hudson.remoting.RemoteClassLoader$IClassLoader.fetch3[java.lang.String]: 1945
  • received 1.2Mb

In other words a 73% drop in the quantity of traffic received in this example.

[jglick]

Maybe deserves a changelog enttry?

[ghost]

Yes, thanks. Missed it. PR inc