8237567: Refactor G1-specific code in shared VM_CollectForMetadataAllocation

Reviewed-by: ayang, tschatzl

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -2236,6 +2236,18 @@ bool G1CollectedHeap::try_collect(GCCause::Cause cause,
   }
 }
 
+void G1CollectedHeap::start_concurrent_gc_for_metadata_allocation(GCCause::Cause gc_cause) {
+  GCCauseSetter x(this, gc_cause);
+
+  // At this point we are supposed to start a concurrent cycle. We
+  // will do so if one is not already in progress.
+  bool should_start = policy()->force_concurrent_start_if_outside_cycle(gc_cause);
+  if (should_start) {
+    double pause_target = policy()->max_pause_time_ms();
+    do_collection_pause_at_safepoint(pause_target);
+  }
+}
+
 bool G1CollectedHeap::is_in(const void* p) const {
   return is_in_reserved(p) && _hrm.is_available(addr_to_region((HeapWord*)p));
 }

src/hotspot/share/gc/g1/g1CollectedHeap.hpp

@@ -136,7 +136,6 @@ class G1RegionMappingChangedListener : public G1MappingChangedListener {
 };
 
 class G1CollectedHeap : public CollectedHeap {
-  friend class VM_CollectForMetadataAllocation;
   friend class VM_G1CollectForAllocation;
   friend class VM_G1CollectFull;
   friend class VM_G1TryInitiateConcMark;
@@ -1095,6 +1094,8 @@ public:
   // Returns whether this collection actually executed.
   bool try_collect(GCCause::Cause cause, const G1GCCounters& counters_before);
 
+  void start_concurrent_gc_for_metadata_allocation(GCCause::Cause gc_cause);
+
   // True iff an evacuation has failed in the most-recent collection.
   inline bool evacuation_failed() const;
   // True iff the given region encountered an evacuation failure in the most-recent

src/hotspot/share/gc/shared/gcVMOperations.cpp

@@ -203,30 +203,6 @@ VM_CollectForMetadataAllocation::VM_CollectForMetadataAllocation(ClassLoaderData
   AllocTracer::send_allocation_requiring_gc_event(_size * HeapWordSize, GCId::peek());
 }
 
-// Returns true iff concurrent GCs unloads metadata.
-bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
-#if INCLUDE_G1GC
-  if (UseG1GC && ClassUnloadingWithConcurrentMark) {
-    G1CollectedHeap* g1h = G1CollectedHeap::heap();
-    g1h->policy()->collector_state()->set_initiate_conc_mark_if_possible(true);
-
-    GCCauseSetter x(g1h, _gc_cause);
-
-    // At this point we are supposed to start a concurrent cycle. We
-    // will do so if one is not already in progress.
-    bool should_start = g1h->policy()->force_concurrent_start_if_outside_cycle(_gc_cause);
-
-    if (should_start) {
-      double pause_target = g1h->policy()->max_pause_time_ms();
-      g1h->do_collection_pause_at_safepoint(pause_target);
-    }
-    return true;
-  }
-#endif
-
-  return false;
-}
-
 void VM_CollectForMetadataAllocation::doit() {
   SvcGCMarker sgcm(SvcGCMarker::FULL);
 
@@ -243,7 +219,9 @@ void VM_CollectForMetadataAllocation::doit() {
     }
   }
 
-  if (initiate_concurrent_GC()) {
+#if INCLUDE_G1GC
+  if (UseG1GC && ClassUnloadingWithConcurrentMark) {
+    G1CollectedHeap::heap()->start_concurrent_gc_for_metadata_allocation(_gc_cause);
     // For G1 expand since the collection is going to be concurrent.
     _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
     if (_result != NULL) {
@@ -252,6 +230,7 @@ void VM_CollectForMetadataAllocation::doit() {
 
     log_debug(gc)("G1 full GC for Metaspace");
   }
+#endif
 
   // Don't clear the soft refs yet.
   heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);

src/hotspot/share/gc/shared/gcVMOperations.hpp

@@ -244,8 +244,6 @@ class VM_CollectForMetadataAllocation: public VM_GC_Operation {
   virtual VMOp_Type type() const { return VMOp_CollectForMetadataAllocation; }
   virtual void doit();
   MetaWord* result() const       { return _result; }
-
-  bool initiate_concurrent_GC();
 };
 
 class SvcGCMarker : public StackObj {