diff src/share/vm/gc_implementation/g1/concurrentG1Refine.hpp @ 890:6cb8e9df7174

6819077: G1: first GC thread coming late into the GC. Summary: The first worker thread is delayed when entering the GC because it clears the card count table that is used in identifying hot cards. Replace the card count table with a dynamically sized evicting hash table that includes an epoch based counter. Reviewed-by: iveresov, tonyp
author johnc
date Tue, 04 Aug 2009 16:00:17 -0700
parents 15c5903cf9e1
children 035d2e036a9b
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/g1/concurrentG1Refine.hpp	Mon Aug 03 12:59:30 2009 -0700
+++ b/src/share/vm/gc_implementation/g1/concurrentG1Refine.hpp	Tue Aug 04 16:00:17 2009 -0700
@@ -29,18 +29,77 @@
 class ConcurrentG1Refine: public CHeapObj {
   ConcurrentG1RefineThread** _threads;
   int _n_threads;
+
   // The cache for card refinement.
-  bool     _use_cache;
-  bool     _def_use_cache;
-  size_t _n_periods;
-  size_t _total_cards;
-  size_t _total_travs;
+  bool   _use_cache;
+  bool   _def_use_cache;
 
-  unsigned char* _card_counts;
-  unsigned       _n_card_counts;
-  const jbyte*   _ct_bot;
-  unsigned*      _cur_card_count_histo;
-  unsigned*      _cum_card_count_histo;
+  size_t _n_periods;    // Used as clearing epoch
+
+  // An evicting cache of the number of times each card
+  // is accessed. Reduces, but does not eliminate, the amount
+  // of duplicated processing of dirty cards.
+
+  enum SomePrivateConstants {
+    epoch_bits           = 32,
+    card_num_shift       = epoch_bits,
+    epoch_mask           = AllBits,
+    card_num_mask        = AllBits,
+
+    // The initial cache size is approximately this fraction
+    // of a maximal cache (i.e. the size needed for all cards
+    // in the heap)
+    InitialCacheFraction = 512
+  };
+
+  const static julong card_num_mask_in_place =
+                        (julong) card_num_mask << card_num_shift;
+
+  typedef struct {
+    julong _value;      // |  card_num   |  epoch   |
+  } CardEpochCacheEntry;
+
+  julong make_epoch_entry(unsigned int card_num, unsigned int epoch) {
+    assert(0 <= card_num && card_num < _max_n_card_counts, "Bounds");
+    assert(0 <= epoch && epoch <= _n_periods, "must be");
+
+    return ((julong) card_num << card_num_shift) | epoch;
+  }
+
+  unsigned int extract_epoch(julong v) {
+    return (v & epoch_mask);
+  }
+
+  unsigned int extract_card_num(julong v) {
+    return (v & card_num_mask_in_place) >> card_num_shift;
+  }
+
+  typedef struct {
+    unsigned char _count;
+    unsigned char _evict_count;
+  } CardCountCacheEntry;
+
+  CardCountCacheEntry* _card_counts;
+  CardEpochCacheEntry* _card_epochs;
+
+  // The current number of buckets in the card count cache
+  unsigned _n_card_counts;
+
+  // The max number of buckets required for the number of
+  // cards for the entire reserved heap
+  unsigned _max_n_card_counts;
+
+  // Possible sizes of the cache: odd primes that roughly double in size.
+  // (See jvmtiTagMap.cpp).
+  static int _cc_cache_sizes[];
+
+  // The index in _cc_cache_sizes corresponding to the size of
+  // _card_counts.
+  int _cache_size_index;
+
+  bool _expand_card_counts;
+
+  const jbyte* _ct_bot;
 
   jbyte**      _hot_cache;
   int          _hot_cache_size;
@@ -50,12 +109,37 @@
   int          _hot_cache_par_chunk_size;
   volatile int _hot_cache_par_claimed_idx;
 
+  // Needed to workaround 6817995
+  CardTableModRefBS* _ct_bs;
+  G1CollectedHeap*   _g1h;
+
+  // Expands the array that holds the card counts to the next size up
+  void expand_card_count_cache();
+
+  // hash a given key (index of card_ptr) with the specified size
+  static unsigned int hash(size_t key, int size) {
+    return (unsigned int) key % size;
+  }
+
+  // hash a given key (index of card_ptr)
+  unsigned int hash(size_t key) {
+    return hash(key, _n_card_counts);
+  }
+
+  unsigned ptr_2_card_num(jbyte* card_ptr) {
+    return (unsigned) (card_ptr - _ct_bot);
+  }
+
+  jbyte* card_num_2_ptr(unsigned card_num) {
+    return (jbyte*) (_ct_bot + card_num);
+  }
+
   // Returns the count of this card after incrementing it.
-  int add_card_count(jbyte* card_ptr);
+  jbyte* add_card_count(jbyte* card_ptr, int* count, bool* defer);
 
-  void print_card_count_histo_range(unsigned* histo, int from, int to,
-                                    float& cum_card_pct,
-                                    float& cum_travs_pct);
+  // Returns true if this card is in a young region
+  bool is_young_card(jbyte* card_ptr);
+
  public:
   ConcurrentG1Refine();
   ~ConcurrentG1Refine();
@@ -69,7 +153,7 @@
   // If this is the first entry for the slot, writes into the cache and
   // returns NULL.  If it causes an eviction, returns the evicted pointer.
   // Otherwise, its a cache hit, and returns NULL.
-  jbyte* cache_insert(jbyte* card_ptr);
+  jbyte* cache_insert(jbyte* card_ptr, bool* defer);
 
   // Process the cached entries.
   void clean_up_cache(int worker_i, G1RemSet* g1rs);
@@ -93,7 +177,6 @@
   }
 
   void clear_and_record_card_counts();
-  void print_final_card_counts();
 
   static size_t thread_num();
 };