src/share/vm/gc/g1/g1IHOPControl.hpp

rev 9402 : dihop-changes
rev 9403 : imported patch sihop-thomas-review
rev 9404 : imported patch erik-jmasa-review
rev 9405 : imported patch 8136678-implement-adaptive-sizing-algorithm-for-IHOP
rev 9407 : [mq]: erik-jon-review

@@ -96,27 +96,50 @@
 #ifndef PRODUCT
   static void test();
 #endif
 };
 
+// This algorithm tries to return a concurrent mark starting occupancy value that
+// makes sure that during marking the given target occupancy is never exceeded,
+// depending on predictions of current allocation rate and time periods between
+// initial mark and the first mixed gc.
 class G1AdaptiveIHOPControl : public G1IHOPControl {
+  size_t _heap_reserve_percent; // Percentage of maximum heap capacity we should avoid to touch
+  size_t _heap_waste_percent;   // Percentage of free heap that should be considered as waste.
+
   G1Predictions const * _predictor;
 
   TruncatedSeq _marking_times_s;
   TruncatedSeq _allocation_rate_s;
 
   size_t _last_allocation_bytes; // Most recent mutator allocation since last GC.
-  size_t _prev_unrestrained_young_size;
+  // The most recent unrestrained size of the young gen. This is used as an additional
+  // factor in the calculation of the threshold, as the threshold is based on
+  // non-young gen occupancy compared against at the end of GC, but we need to
+  // accommodate the young gen too during that time.
+  // Since we cannot know what young gen sizes are used in the future, we will just
+  // use the current one. We expect that this one will be one with a fairly large size,
+  // as there is no marking or mixed gc that could impact its size too much.
+  size_t _last_unrestrained_young_size;
 
-  size_t _current_threshold;
+  size_t _current_threshold; // Save the most recently calculated threshold value here.
 
   // Updates _current_threshold according to internal state.
-  void recalculate();
+  void calculate();
 
   bool have_enough_data_for_prediction() const;
+
+  // The "actual" target threshold the algorithm wants to keep during and at the
+  // end of marking. This is typically lower than the requested threshold, as the
+  // algorithm needs to consider restrictions by the environment.
+  size_t actual_target_threshold() const;
  public:
-  G1AdaptiveIHOPControl(double ihop_percent, size_t initial_target_occupancy, G1Predictions const* predictor);
+  G1AdaptiveIHOPControl(double ihop_percent,
+                        size_t initial_target_occupancy,
+                        G1Predictions const* predictor,
+                        size_t heap_reserve_percent, // The percentage of total heap capacity that should not be tapped into.
+                        size_t heap_waste_percent);  // The percentage of the free space in the heap that we think is not usable for allocation.
 
   virtual void set_target_occupancy(size_t target_occupancy);
 
   virtual size_t get_conc_mark_start_threshold();