6921087: G1: remove per-GC-thread expansion tables from the fine-grain remembered sets

Summary: Remove the per-thread expansion tables (PosParPRT) and associated expansion and compaction from the fine grain RSet entries. This code has been unused for a while.
Reviewed-by: johnc, brutisso
Contributed-by: NThomas Schatzl <thomas.schatzl@jku.at>

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -4750,9 +4750,6 @@ public:
       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
 
-      // Clean up any par-expanded rem sets.
-      HeapRegionRemSet::par_cleanup();
-
       if (ParallelGCVerbose) {
         MutexLocker x(stats_lock());
         pss.print_termination_stats(worker_id);

src/share/vm/gc_implementation/g1/g1_globals.hpp

@@ -53,6 +53,9 @@
   develop(bool, G1TraceMarkStackOverflow, false,                            \
           "If true, extra debugging code for CM restart for ovflw.")        \
                                                                             \
+  develop(bool, G1TraceHeapRegionRememberedSet, false,                      \
+          "Enables heap region remembered set debug logs")                  \
+                                                                            \
   diagnostic(bool, G1SummarizeConcMark, false,                              \
           "Summarize concurrent mark info")                                 \
                                                                             \

src/share/vm/gc_implementation/g1/heapRegionRemSet.hpp

 /*
- * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -35,7 +35,7 @@ class G1CollectedHeap;
 class G1BlockOffsetSharedArray;
 class HeapRegion;
 class HeapRegionRemSetIterator;
-class PosParPRT;
+class PerRegionTable;
 class SparsePRT;
 
 // Essentially a wrapper around SparsePRTCleanupTask. See
@@ -79,15 +79,14 @@ class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
   size_t      _n_coarse_entries;
   static jint _n_coarsenings;
 
-  PosParPRT** _fine_grain_regions;
-  size_t      _n_fine_entries;
+  PerRegionTable** _fine_grain_regions;
+  size_t           _n_fine_entries;
 
-#define SAMPLE_FOR_EVICTION 1
-#if SAMPLE_FOR_EVICTION
+  // Used to sample a subset of the fine grain PRTs to determine which
+  // PRT to evict and coarsen.
   size_t        _fine_eviction_start;
   static size_t _fine_eviction_stride;
   static size_t _fine_eviction_sample_size;
-#endif
 
   SparsePRT   _sparse_table;
 
@@ -98,21 +97,18 @@ class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
   // Requires "prt" to be the first element of the bucket list appropriate
   // for "hr".  If this list contains an entry for "hr", return it,
   // otherwise return "NULL".
-  PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const;
+  PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
 
-  // Find, delete, and return a candidate PosParPRT, if any exists,
+  // Find, delete, and return a candidate PerRegionTable, if any exists,
   // adding the deleted region to the coarse bitmap.  Requires the caller
   // to hold _m, and the fine-grain table to be full.
-  PosParPRT* delete_region_table();
+  PerRegionTable* delete_region_table();
 
   // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
   // be the correct index for "hr"), delete it and return true; else return
   // false.
   bool del_single_region_table(size_t ind, HeapRegion* hr);
 
-  static jint _cache_probes;
-  static jint _cache_hits;
-
   // Indexed by thread X heap region, to minimize thread contention.
   static int** _from_card_cache;
   static size_t _from_card_cache_max_regions;
@@ -127,10 +123,6 @@ public:
   // sense.
   void add_reference(OopOrNarrowOopStar from, int tid);
 
-  void add_reference(OopOrNarrowOopStar from) {
-    return add_reference(from, 0);
-  }
-
   // Removes any entries shown by the given bitmaps to contain only dead
   // objects.
   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
@@ -233,14 +225,12 @@ public:
 
   static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
 
-  /* Used in the sequential case.  Returns "true" iff this addition causes
-     the size limit to be reached. */
+  // Used in the sequential case.
   void add_reference(OopOrNarrowOopStar from) {
-    _other_regions.add_reference(from);
+    _other_regions.add_reference(from, 0);
   }
 
-  /* Used in the parallel case.  Returns "true" iff this addition causes
-     the size limit to be reached. */
+  // Used in the parallel case.
   void add_reference(OopOrNarrowOopStar from, int tid) {
     _other_regions.add_reference(from, tid);
   }
@@ -253,15 +243,6 @@ public:
   // entries for this region in other remsets.
   void clear();
 
-  // Forget any entries due to pointers from "from_hr".
-  void clear_incoming_entry(HeapRegion* from_hr) {
-    _other_regions.clear_incoming_entry(from_hr);
-  }
-
-#if 0
-  virtual void cleanup() = 0;
-#endif
-
   // Attempt to claim the region.  Returns true iff this call caused an
   // atomic transition from Unclaimed to Claimed.
   bool claim_iter();
@@ -290,12 +271,6 @@ public:
   // Initialize the given iterator to iterate over this rem set.
   void init_iterator(HeapRegionRemSetIterator* iter) const;
 
-#if 0
-  // Apply the "do_card" method to the start address of every card in the
-  // rem set.  Returns false if some application of the closure aborted.
-  virtual bool card_iterate(CardClosure* iter) = 0;
-#endif
-
   // The actual # of bytes this hr_remset takes up.
   size_t mem_size() {
     return _other_regions.mem_size()
@@ -322,10 +297,7 @@ public:
   void print() const;
 
   // Called during a stop-world phase to perform any deferred cleanups.
-  // The second version may be called by parallel threads after then finish
-  // collection work.
   static void cleanup();
-  static void par_cleanup();
 
   // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
   // (Uses it to initialize from_card_cache).
@@ -367,7 +339,7 @@ class HeapRegionRemSetIterator : public CHeapObj {
 
   // Local caching of HRRS fields.
   const BitMap*             _coarse_map;
-  PosParPRT**               _fine_grain_regions;
+  PerRegionTable**          _fine_grain_regions;
 
   G1BlockOffsetSharedArray* _bosa;
   G1CollectedHeap*          _g1h;
@@ -404,8 +376,9 @@ class HeapRegionRemSetIterator : public CHeapObj {
 
   // Index of bucket-list we're working on.
   int _fine_array_index;
+
   // Per Region Table we're doing within current bucket list.
-  PosParPRT* _fine_cur_prt;
+  PerRegionTable* _fine_cur_prt;
 
   /* SparsePRT::*/ SparsePRTIter _sparse_iter;
 
@@ -435,12 +408,4 @@ public:
   }
 };
 
-#if 0
-class CardClosure: public Closure {
-public:
-  virtual void do_card(HeapWord* card_start) = 0;
-};
-
-#endif
-
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP