src/share/vm/runtime/virtualspace.cpp

rev 7765 : 8072434: 8064457: introduces performance regressions in 9-b47
Reviewed-by: coleenp

@@ -501,15 +501,16 @@
 
     // zerobased: Attempt to allocate in the lower 32G.
     // But leave room for the compressed class pointers, which is allocated above
     // the heap.
     char *zerobased_max = (char *)OopEncodingHeapMax;
+    const size_t class_space = align_size_up(CompressedClassSpaceSize, alignment);
     // For small heaps, save some space for compressed class pointer
     // space so it can be decoded with no base.
     if (UseCompressedClassPointers && !UseSharedSpaces &&
-        OopEncodingHeapMax <= KlassEncodingMetaspaceMax) {
-      const size_t class_space = align_size_up(CompressedClassSpaceSize, alignment);
+        OopEncodingHeapMax <= KlassEncodingMetaspaceMax &&
+        (uint64_t)(aligned_heap_base_min_address + size + class_space) <= KlassEncodingMetaspaceMax) {
       zerobased_max = (char *)OopEncodingHeapMax - class_space;
     }
 
     // Give it several tries from top of range to bottom.
     if (aligned_heap_base_min_address + size <= zerobased_max &&    // Zerobased theoretical possible.