rev 3463 : 7114678: G1: various small fixes, code cleanup, and refactoring
Summary: Various cleanups as a prelude to introducing iterators for HeapRegions.
Reviewed-by: johnc
Contributed-by: tonyp

          --- old/src/share/vm/gc_implementation/g1/collectionSetChooser.hpp
          +++ new/src/share/vm/gc_implementation/g1/collectionSetChooser.hpp

   1    1  /*
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  11   11   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12   12   * version 2 for more details (a copy is included in the LICENSE file that
  13   13   * accompanied this code).
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  24   24  
  25   25  #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
  26   26  #define SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
  27   27  
  28   28  #include "gc_implementation/g1/heapRegion.hpp"
  29   29  #include "utilities/growableArray.hpp"
  30   30  
  31   31  class CollectionSetChooser: public CHeapObj {
  32   32  
  33   33    GrowableArray<HeapRegion*> _regions;
  34   34  
  35   35    // Unfortunately, GrowableArray uses ints for length and indexes. To
  36   36    // avoid excessive casting in the rest of the class the following
  37   37    // wrapper methods are provided that use uints.
  38   38  
  39   39    uint regions_length()          { return (uint) _regions.length(); }
  40   40    HeapRegion* regions_at(uint i) { return _regions.at((int) i);     }
  41   41    void regions_at_put(uint i, HeapRegion* hr) {
  42   42      _regions.at_put((int) i, hr);
  43   43    }
  44   44    void regions_at_put_grow(uint i, HeapRegion* hr) {
  45   45      _regions.at_put_grow((int) i, hr);
  46   46    }
  47   47    void regions_trunc_to(uint i)  { _regions.trunc_to((uint) i); }
  48   48  
  49   49    // The index of the next candidate old region to be considered for
  50   50    // addition to the CSet.
  51   51    uint _curr_index;
  52   52  
  53   53    // The number of candidate old regions added to the CSet chooser.
  54   54    uint _length;
  55   55  
  56   56    // Keeps track of the start of the next array chunk to be claimed by
  57   57    // parallel GC workers.
  58   58    uint _first_par_unreserved_idx;
  59   59  
  60   60    // If a region has more live bytes than this threshold, it will not
  61   61    // be added to the CSet chooser and will not be a candidate for
  62   62    // collection.
  63   63    size_t _region_live_threshold_bytes;
  64   64  
  65   65    // The sum of reclaimable bytes over all the regions in the CSet chooser.
  66   66    size_t _remaining_reclaimable_bytes;
  67   67  
  68   68  public:
  69   69  
  70   70    // Return the current candidate region to be considered for
  71   71    // collection without removing it from the CSet chooser.
  72   72    HeapRegion* peek() {
  73   73      HeapRegion* res = NULL;
  74   74      if (_curr_index < _length) {
  75   75        res = regions_at(_curr_index);
  76   76        assert(res != NULL,
  77   77               err_msg("Unexpected NULL hr in _regions at index %u",
  78   78                       _curr_index));
  79   79      }
  80   80      return res;
  81   81    }
  82   82  
  83   83    // Remove the given region from the CSet chooser and move to the
  84   84    // next one. The given region should be the current candidate region
  85   85    // in the CSet chooser.
  86   86    void remove_and_move_to_next(HeapRegion* hr) {
  87   87      assert(hr != NULL, "pre-condition");
  88   88      assert(_curr_index < _length, "pre-condition");
  89   89      assert(regions_at(_curr_index) == hr, "pre-condition");
  90   90      regions_at_put(_curr_index, NULL);
  91   91      assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes,
  92   92             err_msg("remaining reclaimable bytes inconsistent "
  93   93                     "from region: "SIZE_FORMAT" remaining: "SIZE_FORMAT,
  94   94                     hr->reclaimable_bytes(), _remaining_reclaimable_bytes));
  95   95      _remaining_reclaimable_bytes -= hr->reclaimable_bytes();
  96   96      _curr_index += 1;
  97   97    }
  98   98  
  99   99    CollectionSetChooser();
 100  100  
 101  101    void sort_regions();
 102  102  
 103  103    // Determine whether to add the given region to the CSet chooser or
 104  104    // not. Currently, we skip humongous regions (we never add them to
 105  105    // the CSet, we only reclaim them during cleanup) and regions whose
 106  106    // live bytes are over the threshold.
 107  107    bool should_add(HeapRegion* hr) {
 108  108      assert(hr->is_marked(), "pre-condition");
 109  109      assert(!hr->is_young(), "should never consider young regions");
 110  110      return !hr->isHumongous() &&
 111  111              hr->live_bytes() < _region_live_threshold_bytes;
 112  112    }
 113  113  
 114  114    // Calculate the minimum number of old regions we'll add to the CSet
 115  115    // during a mixed GC.
 116  116    uint calc_min_old_cset_length();
 117  117  
 118  118    // Calculate the maximum number of old regions we'll add to the CSet
 119  119    // during a mixed GC.
 120  120    uint calc_max_old_cset_length();
 121  121  
 122  122    // Serial version.
 123  123    void add_region(HeapRegion *hr);
 124  124  
 125  125    // Must be called before calls to claim_array_chunk().
 126  126    // n_regions is the number of regions, chunk_size the chunk size.
 127  127    void prepare_for_par_region_addition(uint n_regions, uint chunk_size);
 128  128    // Returns the first index in a contiguous chunk of chunk_size indexes
 129  129    // that the calling thread has reserved.  These must be set by the
 130  130    // calling thread using set_region() (to NULL if necessary).
 131  131    uint claim_array_chunk(uint chunk_size);
 132  132    // Set the marked array entry at index to hr.  Careful to claim the index
 133  133    // first if in parallel.
 134  134    void set_region(uint index, HeapRegion* hr);
 135  135    // Atomically increment the number of added regions by region_num
 136  136    // and the amount of reclaimable bytes by reclaimable_bytes.
 137  137    void update_totals(uint region_num, size_t reclaimable_bytes);
 138  138  
 139  139    void clear();
 140  140  
 141  141    // Return the number of candidate regions that remain to be collected.
 142  142    uint remaining_regions() { return _length - _curr_index; }
 143  143  
 144  144    // Determine whether the CSet chooser has more candidate regions or not.
 145  145    bool is_empty() { return remaining_regions() == 0; }

 146  146  
 147  147    // Return the reclaimable bytes that remain to be collected on
 148  148    // all the candidate regions in the CSet chooser.
 149  149    size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }
 150  150  
 151  151    // Returns true if the used portion of "_regions" is properly
 152  152    // sorted, otherwise asserts false.
 153  153    void verify() PRODUCT_RETURN;
 154  154  };
 155  155  
      156 +class CSetChooserParUpdater : public StackObj {
      157 +private:
      158 +  CollectionSetChooser* _chooser;
      159 +  bool _parallel;
      160 +  uint _chunk_size;
      161 +  uint _cur_chunk_idx;
      162 +  uint _cur_chunk_end;
      163 +  uint _regions_added;
      164 +  size_t _reclaimable_bytes_added;
      165 +
      166 +public:
      167 +  CSetChooserParUpdater(CollectionSetChooser* chooser,
      168 +                        bool parallel, uint chunk_size) :
      169 +    _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size),
      170 +    _cur_chunk_idx(0), _cur_chunk_end(0),
      171 +    _regions_added(0), _reclaimable_bytes_added(0) { }
      172 +
      173 +  ~CSetChooserParUpdater() {
      174 +    if (_parallel && _regions_added > 0) {
      175 +      _chooser->update_totals(_regions_added, _reclaimable_bytes_added);
      176 +    }
      177 +  }
      178 +
      179 +  void add_region(HeapRegion* hr) {
      180 +    if (_parallel) {
      181 +      if (_cur_chunk_idx == _cur_chunk_end) {
      182 +        _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size);
      183 +        _cur_chunk_end = _cur_chunk_idx + _chunk_size;
      184 +      }
      185 +      assert(_cur_chunk_idx < _cur_chunk_end, "invariant");
      186 +      _chooser->set_region(_cur_chunk_idx, hr);
      187 +      _cur_chunk_idx += 1;
      188 +    } else {
      189 +      _chooser->add_region(hr);
      190 +    }
      191 +    _regions_added += 1;
      192 +    _reclaimable_bytes_added += hr->reclaimable_bytes();
      193 +  }
      194 +
      195 +  bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); }
      196 +};
      197 +
 156  198  #endif // SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
      199 +
    

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