src/share/vm/gc_implementation/parallelScavenge/parallelScavengeHeap.cpp

*** 957,961 ****
--- 957,1002 ----
      old_gen()->object_space()->mangle_unused_area();
      perm_gen()->object_space()->mangle_unused_area();
    }
  }
  #endif
+ 
+ bool ParallelScavengeHeap::try_to_shrink_by_free_ratio(bool isFullGC) {
+   if (MaxHeapFreeRatio >= 100) {
+     // nothing to do in this case
+     return false;
+   }
+ 
+   size_t capacity = old_gen()->capacity_in_bytes() + young_gen()->capacity_in_bytes();
+   size_t used = old_gen()->used_in_bytes() + young_gen()->used_in_bytes();
+   size_t init_size = old_gen()->init_gen_size() + young_gen()->init_gen_size();
+   const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
+   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
+   const double max_tmp = used / minimum_used_percentage;
+   size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
+   maximum_desired_capacity = MAX2(maximum_desired_capacity, init_size);
+ 
+   if (PrintGC && Verbose) {
+     const double free_ratio = 1.0 - (double) used / capacity;
+     gclog_or_tty->print("Shrink by free ratio: ");
+     gclog_or_tty->print("capacity : " SIZE_FORMAT ", ", capacity);
+     gclog_or_tty->print("used : " SIZE_FORMAT ", ", used);
+     gclog_or_tty->print_cr("free ratio : %f.2", free_ratio);
+   }
+ 
+   size_t free_bytes = capacity - used;
+   if (capacity > maximum_desired_capacity && free_bytes > 0) {
+     size_t young_gen_free_bytes = young_gen()->capacity_in_bytes() - young_gen()->used_in_bytes();
+     size_t old_gen_free_bytes = old_gen()->capacity_in_bytes() - old_gen()->used_in_bytes();
+     size_t shrink_bytes = capacity - maximum_desired_capacity;
+     if (isFullGC) {
+       size_t old_gen_shrink_bytes =
+           (size_t) (shrink_bytes * ((double) old_gen_free_bytes / free_bytes));
+       old_gen()->try_to_shrink_by(old_gen_shrink_bytes);
+     }
+     size_t young_gen_shrink_bytes =
+         (size_t) (shrink_bytes * ((double) young_gen_free_bytes / free_bytes));
+     young_gen()->try_to_shrink_by(young_gen_shrink_bytes);
+     return true;
+   }
+   return false;
+ }