Hi Wenei, 
The idea of bindTo()/insertArguments is that you are requesting a partial 
evaluation, so you are asking the VM/JIT to specialize the method handle if the 
method handle is used often. 
So compiling a method handle to a bytecode snippet in that case is the expected 
behavior, not a bug. 

What i do not understand is why you need to have a different method handle for 
each row ? 

Did you try to use invokeWithArguments instead of bindTo().invokeExact() ? 


> De: "Wenlei Xie" <wenlei....@gmail.com>
> À: mlvm-dev@openjdk.java.net
> Envoyé: Mardi 2 Mai 2017 21:29:38
> Objet: Implementing Lambda with Capture support makes Metaspace fills
> LambdaForms$BMH class

> Hi,
> We are implementing Lambda function with capture support in a SQL Engine. We
> currently implement by compiling user-written Lambda Expression into a
> MethodHandle. And use bindTo to captured fields. Thus for each row we will 
> have
> a Bound Method Handle.

> However, we found JVM will generate the byte code Bound Method Handle once 
> it's
> invoked more than 128 times. This cause in some cases (when the table has 
> large
> arrays), the Metaspace fills with generated LambdaForm$BMH class.

> Here is the simple code to reproduce the issue:
> https://github.com/wenleix/BMHTest . It looks we cannot increase
> java.lang.invoke.MethodHandle.CUSTOMIZE_THRESHOLD beyond 128. Any suggestions
> to implement Lambda with Capture Support on JVM?

> Thank you !!

> Best,
> Wenlei

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