Hi,
I observed an issue in my application where it is continuously churning
(loading, then later unloading) LambdaForm MethodHandle classes.
```
[6.289s][info][class,init ] 2754 Initializing
'java/lang/invoke/LambdaForm$MH+0x0000000800e64400' (0x0000000800e64400)
[6.289s][info][class,init ] 2755 Initializing
'java/lang/invoke/LambdaForm$MH+0x0000000800e64800' (0x0000000800e64800)
[6.708s][info][class,nestmates ] LookupDefineClass:
java/lang/invoke/LambdaForm$MH - non-nestmate, hidden, weak, with vm annotations
[6.708s][info][class,nestmates ] LookupDefineClass:
java/lang/invoke/LambdaForm$MH - non-nestmate, hidden, weak, with vm annotations
[6.708s][info][class,load ]
java.lang.invoke.LambdaForm$MH/0x0000000800e64c00 source:
__JVM_LookupDefineClass__
[6.708s][info][class,load ]
java.lang.invoke.LambdaForm$MH/0x0000000800e65000 source:
__JVM_LookupDefineClass__
[6.708s][info][class,init ] 2756 Initializing
'java/lang/invoke/LambdaForm$MH+0x0000000800e64c00' (0x0000000800e64c00)
[6.708s][info][class,init ] 2757 Initializing
'java/lang/invoke/LambdaForm$MH+0x0000000800e65000' (0x0000000800e65000)
... etc.
```
I have created a simple reproducer which demonstrates the issue.
```
// Run with
// JAVA_OPTS="-Xlog:class*=info" groovy test.groovy # java11 or java17
// JAVA_OPTS="-XX:+TraceClassLoading" groovy test.groovy # java8
// Observe a steady stream of LambdaForm classes being loaded, forever.
def foo(Object x) {
if (x.getClass().getName().equals("dummy")) print "dummy"
}
Thread.start { while (true) foo(1) }
while (true) foo("1")
```
I'm using `Groovy Version: 4.0.13 JVM: 17.0.6-internal Vendor: Oracle
Corporation OS: Linux`.
I originally noticed this because the class churning caused a memory leak (at
least partially caused by https://bugs.openjdk.org/browse/JDK-8313678),
but generally this much churn is bound to have negative performance
implications. In my real application this is churning about 10 million classes
per day.
I can avoid the issue when I spot it in my application by tweaking method
arguments, but I'd be interested to know if this is a bug in Groovy and if it
could
be fixed or there are any other more robust mitigations I can use.
I noticed https://issues.apache.org/jira/browse/GROOVY-8298 seems similar but
not exactly the same, I think. The inline cache is not helping here, I'm not
sure if that's perhaps because the receiver is stable and it's the arguments
which change?
Any insight appreciated!
Oli
Amazon Development Centre (London) Ltd. Registered in England and Wales with
registration number 04543232 with its registered office at 1 Principal Place,
Worship Street, London EC2A 2FA, United Kingdom.
