8267185: Add string deduplication support to ParallelGC

src/hotspot/share/gc/parallel/parallelScavengeHeap.hpp

@@ -139,8 +139,8 @@ class ParallelScavengeHeap : public CollectedHeap {
   // Returns JNI_OK on success
   virtual jint initialize();
 
-  void safepoint_synchronize_begin();
-  void safepoint_synchronize_end();
+  virtual void safepoint_synchronize_begin();
+  virtual void safepoint_synchronize_end();
 
   void post_initialize();
   void update_counters();

src/hotspot/share/gc/parallel/psCompactionManager.inline.hpp

@@ -110,15 +110,10 @@ inline void ParCompactionManager::mark_and_push(T* p) {
     if (mark_bitmap()->is_unmarked(obj) && PSParallelCompact::mark_obj(obj)) {
       push(obj);
 
-      if (StringDedup::is_enabled() && java_lang_String::is_instance_inlined(obj) &&
+      if (StringDedup::is_enabled() &&
+          java_lang_String::is_instance_inlined(obj) &&
           psStringDedup::is_candidate_from_mark(obj)) {
-        // Evacuation of objects to old gen may fail and part of the young space is compacted within
-        // the space itself. In this case, we can have strings with age below the threshold deduplicated
-        // without being evacuated to the old gen. We rely on test_and_set_deduplication_requested
-        // to prevent multiple deduplication of such strings.
-        if (!java_lang_String::test_and_set_deduplication_requested(obj)) {
-          _string_dedup_requests.add(obj);
-        }
+        _string_dedup_requests.add(obj);
       }
     }
   }

src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp

@@ -286,10 +286,8 @@ inline oop PSPromotionManager::copy_unmarked_to_survivor_space(oop o,
       // we'll just push its contents
       push_contents(new_obj);
 
-      if (psStringDedup::is_candidate_from_evacuation(o->klass(), new_obj->age(), new_obj_is_tenured)) {
-        if (!java_lang_String::test_and_set_deduplication_requested(o)) {
+      if (psStringDedup::is_candidate_from_evacuation(new_obj, new_obj_is_tenured)) {
           _string_dedup_requests.add(o);
-        }
       }
     }
     return new_obj;

src/hotspot/share/gc/parallel/psStringDedup.hpp

@@ -25,6 +25,7 @@
 #ifndef SHARE_GC_PARALLEL_PSSTRINGDEDUP_HPP
 #define SHARE_GC_PARALLEL_PSSTRINGDEDUP_HPP
 
+#include "classfile/javaClasses.inline.hpp"
 #include "gc/shared/stringdedup/stringDedup.hpp"
 #include "memory/allStatic.hpp"
 #include "oops/oopsHierarchy.hpp"
@@ -35,13 +36,13 @@ class psStringDedup : AllStatic {
   // Candidate selection policy for young during evacuation.
   // If to is young then age should be the new (survivor's) age.
   // if to is old then age should be the age of the copied from object.
-  static bool is_candidate_from_evacuation(const Klass* klass,
-                                           uint age,
+  static bool is_candidate_from_evacuation(oop obj,
                                            bool obj_is_tenured) {
-    return StringDedup::is_enabled_string(klass) &&
+    return StringDedup::is_enabled() &&
+           java_lang_String::is_instance_inlined(obj) &&
            (obj_is_tenured ?
-            StringDedup::is_below_threshold_age(age) :
-            StringDedup::is_threshold_age(age));
+            StringDedup::is_below_threshold_age(obj->age()) :
+            StringDedup::is_threshold_age(obj->age()));
   }
 };
 #endif // SHARE_GC_PARALLEL_PSSTRINGDEDUP_HPP

src/hotspot/share/gc/shared/stringdedup/stringDedupConfig.cpp

@@ -116,7 +116,7 @@ size_t StringDedup::Config::desired_table_size(size_t entry_count) {
 bool StringDedup::Config::ergo_initialize() {
   if (!UseStringDeduplication) {
     return true;
-  } else if (UseEpsilonGC || UseSerialGC) {
+  } else if (!UseG1GC && !UseShenandoahGC && !UseZGC && !UseParallelGC) {
     // String deduplication requested but not supported by the selected GC.
     // Warn and force disable, but don't error except in debug build with
     // incorrect default.