8343218: Add option to disable allocating interface and abstract classes in non-class metaspace

src/hotspot/share/oops/instanceKlass.cpp

@@ -472,7 +472,7 @@ InstanceKlass* InstanceKlass::allocate_instance_klass(const ClassFileParser& par
   assert(loader_data != nullptr, "invariant");
 
   InstanceKlass* ik;
-  const bool use_class_space = parser.klass_needs_narrow_id();
+  const bool use_class_space = UseClassMetaspaceForAllClasses || parser.klass_needs_narrow_id();
 
   // Allocation
   if (parser.is_instance_ref_klass()) {

src/hotspot/share/oops/klass.inline.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -182,6 +182,6 @@ inline bool Klass::needs_narrow_id() const {
   // never instantiated classes out of class space lessens the class space pressure.
   // For more details, see JDK-8338526.
   // Note: don't call this function before access flags are initialized.
-  return !is_abstract() && !is_interface();
+  return UseClassMetaspaceForAllClasses || (!is_abstract() && !is_interface());
 }
 #endif // SHARE_OOPS_KLASS_INLINE_HPP

src/hotspot/share/runtime/globals.hpp

@@ -2000,6 +2000,10 @@ const int ObjectAlignmentInBytes = 8;
   develop(uint, BinarySearchThreshold, 16,                                  \
           "Minimal number of elements in a sorted collection to prefer"     \
           "binary search over simple linear search." )                      \
+                                                                            \
+  product(bool, UseClassMetaspaceForAllClasses, false, DIAGNOSTIC,          \
+          "Use the class metaspace for all classes including "              \
+          "abstract and interface classes.")                                \
 
 // end of RUNTIME_FLAGS
 

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotMetaspaceConstantImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -95,7 +95,7 @@ public boolean isCompressible() {
     }
 
     private boolean canBeStoredInCompressibleMetaSpace() {
-        if (metaspaceObject instanceof HotSpotResolvedJavaType t && !t.isArray()) {
+        if (!HotSpotVMConfig.config().useClassMetaspaceForAllClasses && metaspaceObject instanceof HotSpotResolvedJavaType t && !t.isArray()) {
             // As of JDK-8338526, interface and abstract types are not stored
             // in compressible metaspace.
             return !t.isInterface() && !t.isAbstract();

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotVMConfig.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -67,6 +67,8 @@ static String getHostArchitectureName() {
 
     final boolean useCompressedOops = getFlag("UseCompressedOops", Boolean.class);
 
+    final boolean useClassMetaspaceForAllClasses = getFlag("UseClassMetaspaceForAllClasses", Boolean.class);
+
     final int objectAlignment = getFlag("ObjectAlignmentInBytes", Integer.class);
 
     final int klassOffsetInBytes = getFieldValue("CompilerToVM::Data::oopDesc_klass_offset_in_bytes", Integer.class, "int");