From fbb50f5c6c2afca959c38ca8432d7b32c94d6f92 Mon Sep 17 00:00:00 2001
From: Albert Mingkun Yang <ayang@openjdk.org>
Date: Thu, 30 Apr 2026 09:39:12 +0000
Subject: [PATCH] 8383564: Avoid reloading klass when transforming stack chunks

Reviewed-by: stefank, tschatzl
---
 src/hotspot/share/gc/g1/g1ParScanThreadState.cpp            | 2 +-
 src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp | 2 +-
 src/hotspot/share/gc/serial/defNewGeneration.cpp            | 5 +++--
 src/hotspot/share/gc/shared/continuationGCSupport.hpp       | 3 +++
 .../share/gc/shared/continuationGCSupport.inline.hpp        | 6 +++++-
 5 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/hotspot/share/gc/g1/g1ParScanThreadState.cpp b/src/hotspot/share/gc/g1/g1ParScanThreadState.cpp
index 50438c641c2..45e1b25cb95 100644
--- a/src/hotspot/share/gc/g1/g1ParScanThreadState.cpp
+++ b/src/hotspot/share/gc/g1/g1ParScanThreadState.cpp
@@ -444,7 +444,7 @@ void G1ParScanThreadState::do_iterate_object(oop const obj,
       return;
     }
 
-    ContinuationGCSupport::transform_stack_chunk(obj);
+    ContinuationGCSupport::transform_stack_chunk(obj, klass);
 
     // Check for deduplicating young Strings.
     if (G1StringDedup::is_candidate_from_evacuation(klass,
diff --git a/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp b/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
index 47970ac25cb..4b9edeb7072 100644
--- a/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
+++ b/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
@@ -292,7 +292,7 @@ inline oop PSPromotionManager::copy_unmarked_to_survivor_space(oop o,
       assert(young_space()->contains(new_obj), "Attempt to push non-promoted obj");
     }
 
-    ContinuationGCSupport::transform_stack_chunk(new_obj);
+    ContinuationGCSupport::transform_stack_chunk(new_obj, klass);
 
     // Do the size comparison first with new_obj_size, which we
     // already have. Hopefully, only a few objects are larger than
diff --git a/src/hotspot/share/gc/serial/defNewGeneration.cpp b/src/hotspot/share/gc/serial/defNewGeneration.cpp
index ec3726d1dce..0a98d099744 100644
--- a/src/hotspot/share/gc/serial/defNewGeneration.cpp
+++ b/src/hotspot/share/gc/serial/defNewGeneration.cpp
@@ -698,7 +698,8 @@ void DefNewGeneration::handle_promotion_failure(oop old) {
 oop DefNewGeneration::copy_to_survivor_space(oop old) {
   assert(is_in_reserved(old) && !old->is_forwarded(),
          "shouldn't be scavenging this oop");
-  size_t s = old->size();
+  Klass* klass = old->klass();
+  size_t s = old->size_given_klass(klass);
   oop obj = nullptr;
 
   // Try allocating obj in to-space (unless too old)
@@ -725,7 +726,7 @@ oop DefNewGeneration::copy_to_survivor_space(oop old) {
   // Copy obj
   Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
 
-  ContinuationGCSupport::transform_stack_chunk(obj);
+  ContinuationGCSupport::transform_stack_chunk(obj, klass);
 
   if (!new_obj_is_tenured) {
     // Increment age if obj still in new generation
diff --git a/src/hotspot/share/gc/shared/continuationGCSupport.hpp b/src/hotspot/share/gc/shared/continuationGCSupport.hpp
index dda983e0bd8..8aa0245201d 100644
--- a/src/hotspot/share/gc/shared/continuationGCSupport.hpp
+++ b/src/hotspot/share/gc/shared/continuationGCSupport.hpp
@@ -28,6 +28,8 @@
 #include "memory/allStatic.hpp"
 #include "oops/oopsHierarchy.hpp"
 
+class Klass;
+
 class ContinuationGCSupport : public AllStatic {
 public:
   // Relativize the given oop if it is a stack chunk.
@@ -35,6 +37,7 @@ public:
   // Relativize and transform to use a bitmap for future oop iteration for the
   // given oop if it is a stack chunk.
   static void transform_stack_chunk(oop obj);
+  static void transform_stack_chunk(oop obj, Klass* klass);
 };
 
 #endif // SHARE_GC_SHARED_CONTINUATIONGCSUPPORT_HPP
diff --git a/src/hotspot/share/gc/shared/continuationGCSupport.inline.hpp b/src/hotspot/share/gc/shared/continuationGCSupport.inline.hpp
index 72a828b7396..321ef51f9ae 100644
--- a/src/hotspot/share/gc/shared/continuationGCSupport.inline.hpp
+++ b/src/hotspot/share/gc/shared/continuationGCSupport.inline.hpp
@@ -43,7 +43,11 @@ inline bool ContinuationGCSupport::relativize_stack_chunk(oop obj) {
 }
 
 inline void ContinuationGCSupport::transform_stack_chunk(oop obj) {
-  if (!obj->is_stackChunk()) {
+  transform_stack_chunk(obj, obj->klass());
+}
+
+inline void ContinuationGCSupport::transform_stack_chunk(oop obj, Klass* klass) {
+  if (!klass->is_stack_chunk_instance_klass()) {
     return;
   }