7196103: NPG: Unable to allocate bit map for parallel garbage collection for the requested heap size

Don't allocate huge class metaspace size by default on x64

Reviewed-by: stefank, jmasa, kvn

hotspot/src/share/vm/memory/metaspace.cpp

@@ -2779,19 +2779,22 @@ void Metaspace::initialize_class_space(ReservedSpace rs) {
   _class_space_list = new VirtualSpaceList(rs);
 }
 
-// Class space probably needs a lot less than data space
-const int class_space_divisor = 4;
 
 void Metaspace::initialize(Mutex* lock, size_t initial_size) {
-  // Use SmallChunk size if not specified, adjust class to smaller size if so.
+  // Use SmallChunk size if not specified.   If specified, use this size for
+  // the data metaspace.
   size_t word_size;
   size_t class_word_size;
   if (initial_size == 0) {
     word_size = (size_t) SpaceManager::SmallChunk;
-    class_word_size = word_size;
+    class_word_size = (size_t) SpaceManager::SmallChunk;
   } else {
     word_size = initial_size;
-    class_word_size = initial_size/class_space_divisor;
+    // Make the first class chunk bigger than a medium chunk so it's not put
+    // on the medium chunk list.   The next chunk will be small and progress
+    // from there.  This size calculated by -version.
+    class_word_size = MIN2((size_t)SpaceManager::MediumChunk*5,
+                           (ClassMetaspaceSize/BytesPerWord)*2);
   }
 
   assert(space_list() != NULL,

hotspot/src/share/vm/memory/universe.cpp

@@ -858,7 +858,7 @@ jint Universe::initialize_heap() {
 ReservedSpace Universe::reserve_heap(size_t heap_size, size_t alignment) {
   // Add in the class metaspace area so the classes in the headers can
   // be compressed the same as instances.
-  size_t total_reserved = heap_size + ClassMetaspaceSize;
+  size_t total_reserved = align_size_up(heap_size + ClassMetaspaceSize, alignment);
   char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
 
   ReservedHeapSpace total_rs(total_reserved, alignment, UseLargePages, addr);

hotspot/src/share/vm/runtime/arguments.cpp

@@ -1427,6 +1427,16 @@ void Arguments::set_ergonomics_flags() {
     // if (FLAG_IS_DEFAULT(UseCompressedKlassPointers)) {
     //   FLAG_SET_ERGO(bool, UseCompressedKlassPointers, true);
     // }
+    // Set the ClassMetaspaceSize to something that will not need to be
+    // expanded, since it cannot be expanded.
+    if (UseCompressedKlassPointers && FLAG_IS_DEFAULT(ClassMetaspaceSize)) {
+      // 100,000 classes seems like a good size, so 100M assumes around 1K
+      // per klass.   The vtable and oopMap is embedded so we don't have a fixed
+      // size per klass.   Eventually, this will be parameterized because it
+      // would also be useful to determine the optimal size of the
+      // systemDictionary.
+      FLAG_SET_ERGO(uintx, ClassMetaspaceSize, 100*M);
+    }
   }
   // Also checks that certain machines are slower with compressed oops
   // in vm_version initialization code.
@@ -1965,6 +1975,9 @@ bool Arguments::check_vm_args_consistency() {
 
   status = status && verify_object_alignment();
 
+  status = status && verify_min_value(ClassMetaspaceSize, 1*M,
+                                      "ClassMetaspaceSize");
+
   return status;
 }
 
@@ -2916,7 +2929,7 @@ void Arguments::set_shared_spaces_flags() {
                             (UseLargePages && FLAG_IS_CMDLINE(UseLargePages));
   if (cannot_share) {
     if (must_share) {
-        warning("disabling large pages%s"
+        warning("disabling large pages %s"
                 "because of %s", "" LP64_ONLY("and compressed oops "),
                 DumpSharedSpaces ? "-Xshare:dump" : "-Xshare:on");
         FLAG_SET_CMDLINE(bool, UseLargePages, false);

hotspot/src/share/vm/runtime/globals.hpp

@@ -2993,7 +2993,7 @@ class CommandLineFlags {
   product(uintx, MaxMetaspaceSize, max_uintx,                               \
           "Maximum size of Metaspaces (in bytes)")                          \
                                                                             \
-  product(uintx, ClassMetaspaceSize, NOT_LP64(1*M) LP64_ONLY(512*M),        \
+  product(uintx, ClassMetaspaceSize, 2*M,                                   \
           "Maximum size of InstanceKlass area in Metaspace used for "       \
           "UseCompressedKlassPointers")                                     \
                                                                             \