8317350: Move code cache purging out of CodeCache::UnloadingScope

Reviewed-by: ayang, iwalulya

Author: Thomas Schatzl

src/hotspot/share/code/codeCache.cpp

@@ -1036,7 +1036,6 @@ CodeCache::UnloadingScope::UnloadingScope(BoolObjectClosure* is_alive)
 CodeCache::UnloadingScope::~UnloadingScope() {
   IsUnloadingBehaviour::set_current(_saved_behaviour);
   DependencyContext::cleaning_end();
-  CodeCache::flush_unlinked_nmethods();
 }
 
 void CodeCache::verify_oops() {

src/hotspot/share/code/codeCache.hpp

@@ -179,10 +179,7 @@ class CodeCache : AllStatic {
 
   // GC support
   static void verify_oops();
-  // If any oops are not marked this method unloads (i.e., breaks root links
-  // to) any unmarked codeBlobs in the cache.  Sets "marked_for_unloading"
-  // to "true" iff some code got unloaded.
-  // "unloading_occurred" controls whether metadata should be cleaned because of class unloading.
+  // Scope object managing code cache unloading behavior.
   class UnloadingScope: StackObj {
     ClosureIsUnloadingBehaviour _is_unloading_behaviour;
     IsUnloadingBehaviour*       _saved_behaviour;

src/hotspot/share/gc/g1/g1ConcurrentMark.cpp

@@ -1694,9 +1694,12 @@ void G1ConcurrentMark::weak_refs_work() {
   // Unload Klasses, String, Code Cache, etc.
   if (ClassUnloadingWithConcurrentMark) {
     GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
-    CodeCache::UnloadingScope scope(&g1_is_alive);
-    bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm);
-    _g1h->complete_cleaning(purged_classes);
+    {
+      CodeCache::UnloadingScope scope(&g1_is_alive);
+      bool unloading_occurred = SystemDictionary::do_unloading(_gc_timer_cm);
+      _g1h->complete_cleaning(unloading_occurred);
+    }
+    CodeCache::flush_unlinked_nmethods();
   }
 }
 

src/hotspot/share/gc/g1/g1FullCollector.cpp

@@ -319,10 +319,13 @@ void G1FullCollector::phase1_mark_live_objects() {
   // Class unloading and cleanup.
   if (ClassUnloading) {
     GCTraceTime(Debug, gc, phases) debug("Phase 1: Class Unloading and Cleanup", scope()->timer());
-    CodeCache::UnloadingScope unloading_scope(&_is_alive);
-    // Unload classes and purge the SystemDictionary.
-    bool purged_class = SystemDictionary::do_unloading(scope()->timer());
-    _heap->complete_cleaning(purged_class);
+    {
+      CodeCache::UnloadingScope unloading_scope(&_is_alive);
+      // Unload classes and purge the SystemDictionary.
+      bool unloading_occurred = SystemDictionary::do_unloading(scope()->timer());
+      _heap->complete_cleaning(unloading_occurred);
+    }
+    CodeCache::flush_unlinked_nmethods();
   }
 
   {

src/hotspot/share/gc/parallel/psParallelCompact.cpp

@@ -2052,19 +2052,26 @@ void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
 
   {
     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
-    CodeCache::UnloadingScope scope(is_alive_closure());
 
-    // Follow system dictionary roots and unload classes.
-    bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
+    bool unloading_occurred;
+    {
+      CodeCache::UnloadingScope scope(is_alive_closure());
+
+      // Follow system dictionary roots and unload classes.
+      unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
+
+      // Unload nmethods.
+      CodeCache::do_unloading(unloading_occurred);
+    }
 
-    // Unload nmethods.
-    CodeCache::do_unloading(purged_class);
+    // Release unloaded nmethods's memory.
+    CodeCache::flush_unlinked_nmethods();
 
     // Prune dead klasses from subklass/sibling/implementor lists.
-    Klass::clean_weak_klass_links(purged_class);
+    Klass::clean_weak_klass_links(unloading_occurred);
 
     // Clean JVMCI metadata handles.
-    JVMCI_ONLY(JVMCI::do_unloading(purged_class));
+    JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
   }
 
   {

src/hotspot/share/gc/serial/genMarkSweep.cpp

@@ -199,19 +199,26 @@ void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
 
   {
     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer());
-    CodeCache::UnloadingScope scope(&is_alive);
 
-    // Unload classes and purge the SystemDictionary.
-    bool purged_class = SystemDictionary::do_unloading(gc_timer());
+    bool unloading_occurred;
+    {
+      CodeCache::UnloadingScope scope(&is_alive);
 
-    // Unload nmethods.
-    CodeCache::do_unloading(purged_class);
+      // Unload classes and purge the SystemDictionary.
+      unloading_occurred = SystemDictionary::do_unloading(gc_timer());
+
+      // Unload nmethods.
+      CodeCache::do_unloading(unloading_occurred);
+    }
+
+    // Release unloaded nmethod's memory.
+    CodeCache::flush_unlinked_nmethods();
 
     // Prune dead klasses from subklass/sibling/implementor lists.
-    Klass::clean_weak_klass_links(purged_class);
+    Klass::clean_weak_klass_links(unloading_occurred);
 
     // Clean JVMCI metadata handles.
-    JVMCI_ONLY(JVMCI::do_unloading(purged_class));
+    JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
   }
 
   {

src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp

@@ -1811,14 +1811,18 @@ void ShenandoahHeap::stw_unload_classes(bool full_gc) {
                                           ShenandoahPhaseTimings::full_gc_purge_class_unload :
                                           ShenandoahPhaseTimings::degen_gc_purge_class_unload;
     ShenandoahIsAliveSelector is_alive;
-    CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
-    ShenandoahGCPhase gc_phase(phase);
-    ShenandoahGCWorkerPhase worker_phase(phase);
-    bool purged_class = SystemDictionary::do_unloading(gc_timer());
-
-    uint num_workers = _workers->active_workers();
-    ShenandoahClassUnloadingTask unlink_task(phase, num_workers, purged_class);
-    _workers->run_task(&unlink_task);
+    {
+      CodeCache::UnloadingScope scope(is_alive.is_alive_closure());
+      ShenandoahGCPhase gc_phase(phase);
+      ShenandoahGCWorkerPhase worker_phase(phase);
+      bool unloading_occurred = SystemDictionary::do_unloading(gc_timer());
+
+      uint num_workers = _workers->active_workers();
+      ShenandoahClassUnloadingTask unlink_task(phase, num_workers, unloading_occurred);
+      _workers->run_task(&unlink_task);
+    }
+    // Release unloaded nmethods's memory.
+    CodeCache::flush_unlinked_nmethods();
   }
 
   {