Oliver Gillespie created GROOVY-11152:
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Summary: Indy churning through LambdaForm classes
Key: GROOVY-11152
URL: https://issues.apache.org/jira/browse/GROOVY-11152
Project: Groovy
Issue Type: Improvement
Components: Compiler
Affects Versions: 4.0.13
Reporter: Oliver Gillespie
I observed an issue in my application where it is continuously churning
(loading, then later unloading) LambdaForm MethodHandle classes.
Note: some discussion on this in
https://lists.apache.org/thread/qmgsokwys9fkcozwq9vlmgnry14mdjwl.
{code:java}
[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.{code}
I have created a simple reproducer which demonstrates the issue.
{code:java}
// 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(List<String> x) { }
def bar(List<String> x) { foo(x) }
List<String> l1 = new ArrayList();
List<String> l2 = new LinkedList();
while (true) {
bar(l1)
127.times { bar(l2) }
}{code}
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|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?
I added logging to the sameClasses guard inserted in the invocation, and it's
failing the guard because the argument types keep changing between LinkedList
and ArrayList.
I believe this is a performance issue, as well as the high churn being likely
to highlight bugs or issues in the JVM and thinks like attached profiling
agents.
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