*** old/src/share/vm/gc_implementation/g1/heapRegion.cpp	Thu Aug 29 14:32:01 2013
--- new/src/share/vm/gc_implementation/g1/heapRegion.cpp	Thu Aug 29 14:32:01 2013

*** 147,168 ****
--- 147,161 ----
  
  // The automatic region size calculation will try to have around this
  // many regions in the heap (based on the min heap size).
  #define TARGET_REGION_NUMBER          2048
  
! void HeapRegion::setup_heap_region_size(uintx min_heap_size) {
    // region_size in bytes
! void HeapRegion::setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size) {
    uintx region_size = G1HeapRegionSize;
    if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
      // We base the automatic calculation on the min heap size. This
      // can be problematic if the spread between min and max is quite
      // wide, imagine -Xms128m -Xmx32g. But, if we decided it based on
      // the max size, the region size might be way too large for the
      // min size. Either way, some users might have to set the region
      // size manually for some -Xms / -Xmx combos.
  
      region_size = MAX2(min_heap_size / TARGET_REGION_NUMBER,
+     size_t average_heap_size = (initial_heap_size + max_heap_size) / 2;
+     region_size = MAX2(average_heap_size / TARGET_REGION_NUMBER,
                         (uintx) MIN_REGION_SIZE);
    }
  
    int region_size_log = log2_long((jlong) region_size);
    // Recalculate the region size to make sure it's a power of