8350758

Hi all,

  please review this fix to recent JDK-8349906 to use the current
survivor rate in the accumulated survivor rate for initializing newly
allocated entries as well.

Testing: gha

Thanks,
  Thomas

src/hotspot/share/gc/g1/g1SurvRateGroup.cpp

@@ -68,22 +68,19 @@ void G1SurvRateGroup::stop_adding_regions() {
     _accum_surv_rate_pred = REALLOC_C_HEAP_ARRAY(double, _accum_surv_rate_pred, _num_added_regions, mtGC);
     _surv_rate_predictors = REALLOC_C_HEAP_ARRAY(TruncatedSeq*, _surv_rate_predictors, _num_added_regions, mtGC);
 
-    // Assume that the prediction for the newly added regions is the same as the
-    // ones at the (current) end of the array. Particularly predictions at the end
-    // of this array fairly seldom get updated, so having a better initial value
-    // that is at least somewhat related to the actual application is preferable.
-    double new_pred = _stats_arrays_length > 1
-                    ? _accum_surv_rate_pred[_stats_arrays_length - 1] - _accum_surv_rate_pred[_stats_arrays_length - 2]
-                    : InitialSurvivorRate;
-
     for (size_t i = _stats_arrays_length; i < _num_added_regions; ++i) {
       // Initialize predictors and accumulated survivor rate predictions.
       _surv_rate_predictors[i] = new TruncatedSeq(10);
       if (i == 0) {
         _surv_rate_predictors[i]->add(InitialSurvivorRate);
         _accum_surv_rate_pred[i] = 0.0;
       } else {
-        _surv_rate_predictors[i]->add(_surv_rate_predictors[i-1]->last());
+        // Assume that the prediction for the newly added regions is the same as the
+        // ones at the (current) end of the array. Particularly predictions at the end
+        // of this array fairly seldom get updated, so having a better initial value
+        // that is at least somewhat related to the actual application is preferable.
+        double new_pred = _surv_rate_predictors[i-1]->last();
+        _surv_rate_predictors[i]->add(new_pred);
         _accum_surv_rate_pred[i] = _accum_surv_rate_pred[i-1] + new_pred;
       }
     }