src/share/vm/memory/collectorPolicy.cpp

*** 46,55 ****
--- 46,59 ----
  #endif // INCLUDE_ALL_GCS
  
  // CollectorPolicy methods.
  
  void CollectorPolicy::initialize_flags() {
+   if (MaxHeapSize < InitialHeapSize) {
+     vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
+   }
+     
    if (MetaspaceSize > MaxMetaspaceSize) {
      MaxMetaspaceSize = MetaspaceSize;
    }
    MetaspaceSize = MAX2(min_alignment(), align_size_down_(MetaspaceSize, min_alignment()));
    // Don't increase Metaspace size limit above specified.
*** 231,243 ****
  
  void TwoGenerationCollectorPolicy::initialize_flags() {
    GenCollectorPolicy::initialize_flags();
  
    OldSize = align_size_down(OldSize, min_alignment());
-   if (NewSize + OldSize > MaxHeapSize) {
-     MaxHeapSize = NewSize + OldSize;
-   }
  
    if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
      // NewRatio will be used later to set the young generation size so we use
      // it to calculate how big the heap should be based on the requested OldSize
      // and NewRatio.
--- 235,244 ----
*** 248,257 ****
--- 249,279 ----
      MaxHeapSize = calculated_heapsize;
      InitialHeapSize = calculated_heapsize;
    }
    MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
  
+   // adjust max heap size if necessary
+   if (NewSize + OldSize > MaxHeapSize) {
+     if (FLAG_IS_CMDLINE(MaxHeapSize)) {
+       // somebody set a maximum heap size with the intention that we should not
+       // exceed it. Adjust New/OldSize as necessary.
+       uintx calculated_size = NewSize + OldSize;
+       double shrink_factor = (double) MaxHeapSize / calculated_size;
+       // align
+       NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
+       // OldSize is already aligned because above we aligned MaxHeapSize to
+       // max_alignment(), and we just made sure that NewSize is aligned to
+       // min_alignment(). In initialize_flags() we verified that max_alignment()
+       // is a multiple of min_alignment().
+       OldSize = MaxHeapSize - NewSize;
+     } else {
+       MaxHeapSize = NewSize + OldSize;
+     }
+   }
+   // need to do this again
+   MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
+ 
    always_do_update_barrier = UseConcMarkSweepGC;
  
    // Check validity of heap flags
    assert(OldSize     % min_alignment() == 0, "old space alignment");
    assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");