From f60cf5832e5c3564fb7377d0f45bdedf456f589b Mon Sep 17 00:00:00 2001
From: Stefan Karlsson <stefank@openjdk.org>
Date: Mon, 11 May 2026 11:37:09 +0000
Subject: [PATCH] 8384143: ZGC: Add minor performance improvment to oop
 iteration during flip promotion

Reviewed-by: ayang, sjohanss
---
 src/hotspot/share/gc/z/zIterator.hpp        |  5 ++++
 src/hotspot/share/gc/z/zIterator.inline.hpp | 28 ++++++++++++++++-----
 src/hotspot/share/gc/z/zRelocate.cpp        |  2 +-
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/hotspot/share/gc/z/zIterator.hpp b/src/hotspot/share/gc/z/zIterator.hpp
index e048002e52e..0e9ef808dff 100644
--- a/src/hotspot/share/gc/z/zIterator.hpp
+++ b/src/hotspot/share/gc/z/zIterator.hpp
@@ -31,11 +31,14 @@ class ZIterator : AllStatic {
 private:
   static bool is_invisible_object(oop obj);
   static bool is_invisible_object_array(oop obj);
+  static bool is_invisible_object_array(oop obj, Klass* klass);
 
 public:
   // This iterator skips invisible roots
   template <typename OopClosureT>
   static void oop_iterate_safe(oop obj, OopClosureT* cl);
+  template <typename OopClosureT>
+  static void oop_iterate_safe(oop obj, Klass* klass, OopClosureT* cl);
 
   template <typename OopClosureT>
   static void oop_iterate(oop obj, OopClosureT* cl);
@@ -46,6 +49,8 @@ public:
   // This function skips invisible roots
   template <typename Function>
   static void basic_oop_iterate_safe(oop obj, Function function);
+  template <typename Function>
+  static void basic_oop_iterate_safe(oop obj, Klass* klass, Function function);
 
   template <typename Function>
   static void basic_oop_iterate(oop obj, Function function);
diff --git a/src/hotspot/share/gc/z/zIterator.inline.hpp b/src/hotspot/share/gc/z/zIterator.inline.hpp
index cbfe1a79aaf..6e51929c7b4 100644
--- a/src/hotspot/share/gc/z/zIterator.inline.hpp
+++ b/src/hotspot/share/gc/z/zIterator.inline.hpp
@@ -45,17 +45,27 @@ inline bool ZIterator::is_invisible_object(oop obj) {
 }
 
 inline bool ZIterator::is_invisible_object_array(oop obj) {
-  return obj->klass()->is_objArray_klass() && is_invisible_object(obj);
+  return is_invisible_object_array(obj, obj->klass());
 }
 
-// This iterator skips invisible object arrays
+inline bool ZIterator::is_invisible_object_array(oop obj, Klass* klass) {
+  return klass->is_objArray_klass() && is_invisible_object(obj);
+}
+
+// These iterators skips invisible object arrays
+
 template <typename OopClosureT>
 void ZIterator::oop_iterate_safe(oop obj, OopClosureT* cl) {
+  oop_iterate_safe(obj, obj->klass(), cl);
+}
+
+template <typename OopClosureT>
+void ZIterator::oop_iterate_safe(oop obj, Klass* klass, OopClosureT* cl) {
   // Skip invisible object arrays - we only filter out *object* arrays,
   // because that check is arguably faster than the is_invisible_object
   // check, and primitive arrays are cheap to call oop_iterate on.
-  if (!is_invisible_object_array(obj)) {
-    obj->oop_iterate(cl);
+  if (!is_invisible_object_array(obj, klass)) {
+    OopIteratorClosureDispatch::oop_oop_iterate(cl, obj, klass);
   }
 }
 
@@ -89,11 +99,17 @@ public:
   }
 };
 
-// This function skips invisible roots
+// These functions skip invisible roots
+
 template <typename Function>
 void ZIterator::basic_oop_iterate_safe(oop obj, Function function) {
+  basic_oop_iterate_safe(obj, obj->klass(), function);
+}
+
+template <typename Function>
+void ZIterator::basic_oop_iterate_safe(oop obj, Klass* klass, Function function) {
   ZBasicOopIterateClosure<Function> cl(function);
-  oop_iterate_safe(obj, &cl);
+  oop_iterate_safe(obj, klass, &cl);
 }
 
 template <typename Function>
diff --git a/src/hotspot/share/gc/z/zRelocate.cpp b/src/hotspot/share/gc/z/zRelocate.cpp
index d51cf5abbae..1c2a4078904 100644
--- a/src/hotspot/share/gc/z/zRelocate.cpp
+++ b/src/hotspot/share/gc/z/zRelocate.cpp
@@ -1272,7 +1272,7 @@ public:
     for (ZPage* page; _iter.next(&page);) {
       page->object_iterate([&](oop obj) {
         // Remap oops and add remset if needed
-        ZIterator::basic_oop_iterate_safe(obj, remap_and_maybe_add_remset);
+        ZIterator::basic_oop_iterate_safe(obj, obj->klass(), remap_and_maybe_add_remset);
 
         // String dedup
         string_dedup_context.request(obj);