src/share/vm/gc/g1/g1CollectorPolicy.hpp

*** 252,261 ****
--- 252,276 ----
  
    double predict_yg_surv_rate(int age) const;
  
    double accum_yg_surv_rate_pred(int age) const;
  
+   // When copying, we will likely need more bytes free than is live in the region.
+   // Add some safety margin to factor in the confidence of our guess, and the
+   // natural expected waste.
+   // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
+   // of the calculation: the lower the confidence, the more headroom.
+   // (100 + TargetPLABWastePct) represents the increase in expected bytes during
+   // copying due to anticipated waste in the PLABs.
+   double safety_factor() const {
+     return (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
+   }
+ 
+   // Returns an estimate of the available bytes at end of collection, adjusted by
+   // the safety factor.
+   size_t available_bytes_estimate();
+ 
  protected:
    G1CollectionSet* _collection_set;
    virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
    virtual double other_time_ms(double pause_time_ms) const;