From c470ac79015ad99f1760784cbffcf4b92d5bc8dc Mon Sep 17 00:00:00 2001
From: DXwangg <wangjiawei80@huawei.com>
Date: Wed, 26 Oct 2022 12:52:55 +0800
Subject: [PATCH] qqqqq

---
 .../share/gc/parallel/parallel_globals.hpp     |  6 +++++-
 .../gc/parallel/psPromotionManager.inline.hpp  | 18 ++++++++++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/hotspot/share/gc/parallel/parallel_globals.hpp b/src/hotspot/share/gc/parallel/parallel_globals.hpp
index 5461bf04f..75ee84d4f 100644
--- a/src/hotspot/share/gc/parallel/parallel_globals.hpp
+++ b/src/hotspot/share/gc/parallel/parallel_globals.hpp
@@ -78,6 +78,10 @@
           "Delay in scheduling GC workers (in milliseconds)")               \
                                                                             \
   product(bool, PSChunkLargeArrays, true,                                   \
-          "Process large arrays in chunks")
+          "Process large arrays in chunks")                                 \
+                                                                            \
+  experimental(bool, UsePSRelaxedForwardee, false,                          \
+          "Use the UsePSRelaxedForwardee to enable ps use relaxed"          \
+          "during young gc copying object")
 
 #endif // SHARE_GC_PARALLEL_PARALLEL_GLOBALS_HPP
diff --git a/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp b/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
index cc5a4aa98..5a71ca307 100644
--- a/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
+++ b/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
@@ -35,6 +35,7 @@
 #include "logging/log.hpp"
 #include "oops/access.inline.hpp"
 #include "oops/oop.inline.hpp"
+#include "runtime/prefetch.inline.hpp"
 
 inline PSPromotionManager* PSPromotionManager::manager_array(uint index) {
   assert(_manager_array != NULL, "access of NULL manager_array");
@@ -214,12 +215,21 @@ inline oop PSPromotionManager::copy_to_survivor_space(oop o) {
 
     assert(new_obj != NULL, "allocation should have succeeded");
 
+    Prefetch::write(new_obj, PrefetchCopyIntervalInBytes);
+
     // Copy obj
     Copy::aligned_disjoint_words((HeapWord*)o, (HeapWord*)new_obj, new_obj_size);
 
     // Now we have to CAS in the header.
-    // Make copy visible to threads reading the forwardee.
-    if (o->cas_forward_to(new_obj, test_mark, o->klass()->oop_is_gc_leaf()? memory_order_relaxed : memory_order_release)) {
+    // When use relaxed CAS, cann't gurantee new obj visible for other threads accessing forwardee.
+    // As oop_is_gc_leaf is verified for long time without problems, for gc leaf's benefit, we add
+    // UsePSRelaxedForwardee to enable using relaxed CAS rather than delete oop_is_gc_leaf condition directly.
+#ifdef PRODUCT
+    if (o->cas_forward_to(new_obj, test_mark, (UsePSRelaxedForwardee || o->klass()->oop_is_gc_leaf()) ?
+                                               memory_order_relaxed : memory_order_release)) {
+#else
+    if (o->cas_forward_to(new_obj, test_mark, memory_order_release)) {
+#endif
       // We won any races, we "own" this object.
       assert(new_obj == o->forwardee(), "Sanity");
 
@@ -275,6 +285,10 @@ inline oop PSPromotionManager::copy_to_survivor_space(oop o) {
 
   // This code must come after the CAS test, or it will print incorrect
   // information.
+  // When UsePSRelaxedForwardee is true or object o is gc leaf, CAS failed threads can't access forwardee's content,
+  // as relaxed CAS cann't gurantee new obj's content visible for these CAS failed threads.The below log output is
+  // dangerous.So we just support UsePSRelaxedForwardee and gc leaf in product.
+  // Everywhere access forwardee's content must be careful.
   log_develop_trace(gc, scavenge)("{%s %s " PTR_FORMAT " -> " PTR_FORMAT " (%d)}",
                                   should_scavenge(&new_obj) ? "copying" : "tenuring",
                                   new_obj->klass()->internal_name(), p2i((void *)o), p2i((void *)new_obj), new_obj->size());
-- 
2.30.1 (Apple Git-130)