From a6d763ac87e2f17c8ead83fecfc82693aa37eaea Mon Sep 17 00:00:00 2001
From: Axel Boldt-Christmas <aboldtch@openjdk.org>
Date: Thu, 7 May 2026 13:05:42 +0000
Subject: [PATCH] 8383172: Create AbstractLRUReferencePolicy base class

Reviewed-by: ayang, jsikstro
---
 .../share/gc/shared/referencePolicy.cpp       | 43 +++++--------------
 .../share/gc/shared/referencePolicy.hpp       | 32 +++++++-------
 2 files changed, 27 insertions(+), 48 deletions(-)

diff --git a/src/hotspot/share/gc/shared/referencePolicy.cpp b/src/hotspot/share/gc/shared/referencePolicy.cpp
index d1867291479..6c5f459ebb4 100644
--- a/src/hotspot/share/gc/shared/referencePolicy.cpp
+++ b/src/hotspot/share/gc/shared/referencePolicy.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2026, 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
@@ -28,21 +28,17 @@
 #include "gc/shared/referencePolicy.hpp"
 #include "memory/universe.hpp"
 #include "runtime/globals.hpp"
+#include "utilities/integerCast.hpp"
 
-LRUCurrentHeapPolicy::LRUCurrentHeapPolicy() {
-  setup();
-}
-
-// Capture state (of-the-VM) information needed to evaluate the policy
-void LRUCurrentHeapPolicy::setup() {
-  _max_interval = (Universe::heap()->free_at_last_gc() / M) * SoftRefLRUPolicyMSPerMB;
-  assert(_max_interval >= 0,"Sanity check");
+void AbstractLRUReferencePolicy::set_max_interval(jlong max_interval) {
+  assert(max_interval >= 0, "Sanity check");
+  _max_interval = max_interval;
 }
 
 // The oop passed in is the SoftReference object, and not
 // the object the SoftReference points to.
-bool LRUCurrentHeapPolicy::should_clear_reference(oop p,
-                                                  jlong timestamp_clock) {
+bool AbstractLRUReferencePolicy::should_clear_reference(oop p, jlong timestamp_clock) {
+  assert(_max_interval >= 0, "Forgot to call setup");
   jlong interval = timestamp_clock - java_lang_ref_SoftReference::timestamp(p);
   assert(interval >= 0, "Sanity check");
 
@@ -54,10 +50,9 @@ bool LRUCurrentHeapPolicy::should_clear_reference(oop p,
   return true;
 }
 
-/////////////////////// MaxHeap //////////////////////
-
-LRUMaxHeapPolicy::LRUMaxHeapPolicy() {
-  setup();
+// Capture state (of-the-VM) information needed to evaluate the policy
+void LRUCurrentHeapPolicy::setup() {
+  set_max_interval(integer_cast<jlong>(Universe::heap()->free_at_last_gc() / M) * SoftRefLRUPolicyMSPerMB);
 }
 
 // Capture state (of-the-VM) information needed to evaluate the policy
@@ -66,21 +61,5 @@ void LRUMaxHeapPolicy::setup() {
   max_heap -= Universe::heap()->used_at_last_gc();
   max_heap /= M;
 
-  _max_interval = max_heap * SoftRefLRUPolicyMSPerMB;
-  assert(_max_interval >= 0,"Sanity check");
-}
-
-// The oop passed in is the SoftReference object, and not
-// the object the SoftReference points to.
-bool LRUMaxHeapPolicy::should_clear_reference(oop p,
-                                             jlong timestamp_clock) {
-  jlong interval = timestamp_clock - java_lang_ref_SoftReference::timestamp(p);
-  assert(interval >= 0, "Sanity check");
-
-  // The interval will be zero if the ref was accessed since the last scavenge/gc.
-  if(interval <= _max_interval) {
-    return false;
-  }
-
-  return true;
+  set_max_interval(integer_cast<jlong>(max_heap) * SoftRefLRUPolicyMSPerMB);
 }
diff --git a/src/hotspot/share/gc/shared/referencePolicy.hpp b/src/hotspot/share/gc/shared/referencePolicy.hpp
index cf0382b036b..0fd918fa723 100644
--- a/src/hotspot/share/gc/shared/referencePolicy.hpp
+++ b/src/hotspot/share/gc/shared/referencePolicy.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2026, 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
@@ -56,28 +56,28 @@ class AlwaysClearPolicy : public ReferencePolicy {
   }
 };
 
-class LRUCurrentHeapPolicy : public ReferencePolicy {
+class AbstractLRUReferencePolicy : public ReferencePolicy {
  private:
-  jlong _max_interval;
+  jlong _max_interval = -1;
+
+ protected:
+  void set_max_interval(jlong max_interval);
 
  public:
-  LRUCurrentHeapPolicy();
-
-  // Capture state (of-the-VM) information needed to evaluate the policy
-  void setup();
-  virtual bool should_clear_reference(oop p, jlong timestamp_clock);
+  bool should_clear_reference(oop p, jlong timestamp_clock) final;
+  void setup() override = 0;
 };
 
-class LRUMaxHeapPolicy : public ReferencePolicy {
- private:
-  jlong _max_interval;
-
+class LRUCurrentHeapPolicy : public AbstractLRUReferencePolicy {
  public:
-  LRUMaxHeapPolicy();
-
   // Capture state (of-the-VM) information needed to evaluate the policy
-  void setup();
-  virtual bool should_clear_reference(oop p, jlong timestamp_clock);
+  void setup() final;
+};
+
+class LRUMaxHeapPolicy : public AbstractLRUReferencePolicy {
+ public:
+  // Capture state (of-the-VM) information needed to evaluate the policy
+  void setup() final;
 };
 
 #endif // SHARE_GC_SHARED_REFERENCEPOLICY_HPP