8315933: Serial: Remove empty Generation::ensure_parsability

Reviewed-by: tschatzl, sjohanss

Author: albertnetymk

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

@@ -328,7 +328,7 @@ class CollectedHeap : public CHeapObj<mtGC> {
   // super::ensure_parsability so that the non-generational
   // part of the work gets done. See implementation of
   // CollectedHeap::ensure_parsability and, for instance,
-  // that of GenCollectedHeap::ensure_parsability().
+  // that of ParallelScavengeHeap::ensure_parsability().
   // The argument "retire_tlabs" controls whether existing TLABs
   // are merely filled or also retired, thus preventing further
   // allocation from them and necessitating allocation of new TLABs.

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

@@ -1069,16 +1069,3 @@ void GenCollectedHeap::record_gen_tops_before_GC() {
   }
 }
 #endif  // not PRODUCT
-
-class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
- public:
-  void do_generation(Generation* gen) {
-    gen->ensure_parsability();
-  }
-};
-
-void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
-  CollectedHeap::ensure_parsability(retire_tlabs);
-  GenEnsureParsabilityClosure ep_cl;
-  generation_iterate(&ep_cl, false);
-}

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

@@ -228,9 +228,6 @@ class GenCollectedHeap : public CollectedHeap {
                               size_t requested_size,
                               size_t* actual_size) override;
 
-  // Ensure parsability
-  void ensure_parsability(bool retire_tlabs) override;
-
   // Total number of full collections completed.
   unsigned int total_full_collections_completed() {
     assert(_full_collections_completed <= _total_full_collections,

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

@@ -291,10 +291,6 @@ class Generation: public CHeapObj<mtGC> {
   // Save the high water marks for the used space in a generation.
   virtual void record_spaces_top() {}
 
-  // Some generations may need to be "fixed-up" after some allocation
-  // activity to make them parsable again. The default is to do nothing.
-  virtual void ensure_parsability() {}
-
   // Generations may keep statistics about collection. This method
   // updates those statistics. current_generation is the generation
   // that was most recently collected. This allows the generation to