8236073: G1: Use SoftMaxHeapSize to guide GC heuristics

          --- old/src/hotspot/share/gc/g1/g1HeapSizingPolicy.hpp
          +++ new/src/hotspot/share/gc/g1/g1HeapSizingPolicy.hpp

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  10   10   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  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_GC_G1_G1HEAPSIZINGPOLICY_HPP
  26   26  #define SHARE_GC_G1_G1HEAPSIZINGPOLICY_HPP
  27   27  
  28   28  #include "memory/allocation.hpp"
  29   29  
  30   30  class G1Analytics;
  31   31  class G1CollectedHeap;
  32   32  
  33   33  class G1HeapSizingPolicy: public CHeapObj<mtGC> {
  34   34    // MinOverThresholdForGrowth must be less than the number of recorded
  35   35    // pause times in G1Analytics, representing the minimum number of pause
  36   36    // time ratios that exceed GCTimeRatio before a heap expansion will be triggered.
  37   37    const static uint MinOverThresholdForGrowth = 4;
  38   38  
  39   39    const G1CollectedHeap* _g1h;
  40   40    const G1Analytics* _analytics;
  41   41  
  42   42    const uint _num_prev_pauses_for_heuristics;
  43   43    // Ratio check data for determining if heap growth is necessary.
  44   44    uint _ratio_over_threshold_count;
  45   45    double _ratio_over_threshold_sum;
  46   46    uint _pauses_since_start;
  47   47  
  48   48  
  49   49  protected:

  50   50    G1HeapSizingPolicy(const G1CollectedHeap* g1h, const G1Analytics* analytics);
  51   51  public:
  52   52  
  53   53    // If an expansion would be appropriate, because recent GC overhead had
  54   54    // exceeded the desired limit, return an amount to expand by.
  55   55    virtual size_t expansion_amount();
  56   56  
  57   57    // Clear ratio tracking data used by expansion_amount().
  58   58    void clear_ratio_check_data();
  59   59  
       60 +  // Check if heap size can be shrinked
       61 +  bool can_shrink_heap_size_to(size_t heap_size);
       62 +
  60   63    static G1HeapSizingPolicy* create(const G1CollectedHeap* g1h, const G1Analytics* analytics);
  61   64  };
  62   65  
  63   66  #endif // SHARE_GC_G1_G1HEAPSIZINGPOLICY_HPP
    

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