Garbage collection pressure created by Method.getParameters()

I see that Method.getParameters() is implemented internally in the JDK as a clone() and this generates a lot of garbage collection pressure with Hibernate because of the way that Byte Buddy iterates over method parameters (I think), and also because Hibernate adds static methods to entity proxies with large numbers of parameters.

The offending code path is

ParameterList$ForLoadedExecutable$OfMethod.get(int) line: 320	
ParameterList$ForLoadedExecutable$OfMethod.get(int) line: 307	
AbstractList$Itr.next() line: 358	
TargetMethodAnnotationDrivenBinder.compile(MethodDescription) line: 64	
MethodDelegation$ImplementationDelegate$ForStaticMethod.of(MethodList<?>, MethodDelegationBinder) line: 759	
MethodDelegation$WithCustomProperties.to(TypeDescription) line: 1223	
MethodDelegation$WithCustomProperties.to(Class<?>) line: 1204	
MethodDelegation.to(Class<?>) line: 255	

the problem being that iterating over all method parameters causes a new instance of ParameterDescription.ForLoadedParameter.OfMethod to be created for each parameter, and each one takes a copy of all the parameter types via the JDK Method implementation. I imagine the iteration could be optimized.

I am using Flight Recorder to look at garbage collection pressure which slows down application startup for large (in this case pathological) apps - i.e. with large numbers of entities. I think if it could be optimized here it would have a beneficial effect on less pathological apps.

[gsmet]

@raphw I think a good first step from the ByteBuddy POV is to avoid calling Method#getParameters() more than once per method.

I’ll change our implementation to avoid creating a new method delegation per proxy class.

[raphw]

I added a new build plugin to Byte Buddy that caches method return values on an instance. This is now done for all annotations by classes, methods and fields and for declared members of classes. Completed on master.