/*

 * Copyright (c) 2001, 2010, 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

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

// Forward decl

class ConcurrentG1RefineThread;

class G1RemSet;

class ConcurrentG1Refine: public CHeapObj {

  ConcurrentG1RefineThread** _threads;

  int _n_threads;

  int _n_worker_threads;

 /*

  * The value of the update buffer queue length falls into one of 3 zones:

  * green, yellow, red. If the value is in [0, green) nothing is

  * done, the buffers are left unprocessed to enable the caching effect of the

  * dirtied cards. In the yellow zone [green, yellow) the concurrent refinement

  * threads are gradually activated. In [yellow, red) all threads are

  * running. If the length becomes red (max queue length) the mutators start

  * processing the buffers.

  *

  * There are some interesting cases (when G1UseAdaptiveConcRefinement

  * is turned off):

  * 1) green = yellow = red = 0. In this case the mutator will process all

  *    buffers. Except for those that are created by the deferred updates

  *    machinery during a collection.

  * 2) green = 0. Means no caching. Can be a good way to minimize the

  *    amount of time spent updating rsets during a collection.

  */

  int _green_zone;

  int _yellow_zone;

  int _red_zone;

  int _thread_threshold_step;

  // Reset the threshold step value based of the current zone boundaries.

  void reset_threshold_step();

  // The cache for card refinement.

  bool   _use_cache;

  bool   _def_use_cache;

  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;

  int          _n_hot;

  int          _hot_cache_idx;

  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.

  jbyte* add_card_count(jbyte* card_ptr, int* count, bool* defer);

  // Returns true if this card is in a young region

  bool is_young_card(jbyte* card_ptr);

 public:

  ConcurrentG1Refine();

  ~ConcurrentG1Refine();

  void init(); // Accomplish some initialization that has to wait.

  void stop();

  void reinitialize_threads();

  // Iterate over the conc refine threads

  void threads_do(ThreadClosure *tc);

  // 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, bool* defer);

  // Process the cached entries.

  void clean_up_cache(int worker_i, G1RemSet* g1rs, DirtyCardQueue* into_cset_dcq);

  // Set up for parallel processing of the cards in the hot cache

  void clear_hot_cache_claimed_index() {

    _hot_cache_par_claimed_idx = 0;

  }

  // Discard entries in the hot cache.

  void clear_hot_cache() {

    _hot_cache_idx = 0; _n_hot = 0;

  }

  bool hot_cache_is_empty() { return _n_hot == 0; }

  bool use_cache() { return _use_cache; }

  void set_use_cache(bool b) {

    if (b) _use_cache = _def_use_cache;

    else   _use_cache = false;

  }

  void clear_and_record_card_counts();

  static int thread_num();

  void print_worker_threads_on(outputStream* st) const;

  void set_green_zone(int x)  { _green_zone = x;  }

  void set_yellow_zone(int x) { _yellow_zone = x; }

  void set_red_zone(int x)    { _red_zone = x;    }

  int green_zone() const      { return _green_zone;  }

  int yellow_zone() const     { return _yellow_zone; }

  int red_zone() const        { return _red_zone;    }

  int total_thread_num() const  { return _n_threads;        }

  int worker_thread_num() const { return _n_worker_threads; }

  int thread_threshold_step() const { return _thread_threshold_step; }

};