--- a/make/jprt.gmk	Fri Jul 22 23:42:46 2011 -0700
+++ b/make/jprt.gmk	Sat Jul 23 10:42:20 2011 -0400
@@ -34,13 +34,13 @@
 endif
 
 jprt_build_productEmb:
-	$(MAKE) JAVASE_EMBEDDED=true jprt_build_product
+	$(MAKE) JAVASE_EMBEDDED=true MINIMIZE_RAM_USAGE=true jprt_build_product
 
 jprt_build_debugEmb:
-	$(MAKE) JAVASE_EMBEDDED=true jprt_build_debug
+	$(MAKE) JAVASE_EMBEDDED=true MINIMIZE_RAM_USAGE=true jprt_build_debug
 
 jprt_build_fastdebugEmb:
-	$(MAKE) JAVASE_EMBEDDED=true jprt_build_fastdebug
+	$(MAKE) JAVASE_EMBEDDED=true MINIMIZE_RAM_USAGE=true jprt_build_fastdebug
 
 jprt_build_productOpen:
 	$(MAKE) OPENJDK=true jprt_build_product

--- a/src/share/vm/classfile/javaClasses.cpp	Fri Jul 22 23:42:46 2011 -0700
+++ b/src/share/vm/classfile/javaClasses.cpp	Sat Jul 23 10:42:20 2011 -0400
@@ -1019,6 +1019,16 @@
   compute_offset(_ngroups_offset,     k, vmSymbols::ngroups_name(),     vmSymbols::int_signature());
 }
 
+oop java_lang_Throwable::unassigned_stacktrace() {
+  instanceKlass* ik = instanceKlass::cast(SystemDictionary::Throwable_klass());
+  address addr = ik->static_field_addr(static_unassigned_stacktrace_offset);
+  if (UseCompressedOops) {
+    return oopDesc::load_decode_heap_oop((narrowOop *)addr);
+  } else {
+    return oopDesc::load_decode_heap_oop((oop*)addr);
+  }
+}
+
 oop java_lang_Throwable::backtrace(oop throwable) {
   return throwable->obj_field_acquire(backtrace_offset);
 }
@@ -1044,9 +1054,13 @@
 }
 
 
+void java_lang_Throwable::set_stacktrace(oop throwable, oop st_element_array) {
+  throwable->obj_field_put(stackTrace_offset, st_element_array);
+}
+
 void java_lang_Throwable::clear_stacktrace(oop throwable) {
   assert(JDK_Version::is_gte_jdk14x_version(), "should only be called in >= 1.4");
-  throwable->obj_field_put(stackTrace_offset, NULL);
+  set_stacktrace(throwable, NULL);
 }
 
 
@@ -1340,6 +1354,7 @@
   if (JDK_Version::is_gte_jdk14x_version()) {
     // New since 1.4, clear lazily constructed Java level stacktrace if
     // refilling occurs
+    // This is unnecessary in 1.7+ but harmless
     clear_stacktrace(throwable());
   }
 
@@ -1541,6 +1556,15 @@
     // Bail-out for deep stacks
     if (chunk_count >= max_chunks) break;
   }
+
+  // For Java 7+ we support the Throwable immutability protocol defined for Java 7. This support
+  // was missing in 7u0 so in 7u0 there is a workaround in the Throwable class. That workaround
+  // can be removed in a JDK using this JVM version
+  if (JDK_Version::is_gte_jdk17x_version()) {
+      java_lang_Throwable::set_stacktrace(throwable(), java_lang_Throwable::unassigned_stacktrace());
+      assert(java_lang_Throwable::unassigned_stacktrace() != NULL, "not initialized");
+  }
+
 }
 
 
@@ -2770,6 +2794,7 @@
 int java_lang_Throwable::detailMessage_offset;
 int java_lang_Throwable::cause_offset;
 int java_lang_Throwable::stackTrace_offset;
+int java_lang_Throwable::static_unassigned_stacktrace_offset;
 int java_lang_reflect_AccessibleObject::override_offset;
 int java_lang_reflect_Method::clazz_offset;
 int java_lang_reflect_Method::name_offset;
@@ -2947,6 +2972,7 @@
   java_lang_Throwable::detailMessage_offset = java_lang_Throwable::hc_detailMessage_offset * x + header;
   java_lang_Throwable::cause_offset      = java_lang_Throwable::hc_cause_offset      * x + header;
   java_lang_Throwable::stackTrace_offset = java_lang_Throwable::hc_stackTrace_offset * x + header;
+  java_lang_Throwable::static_unassigned_stacktrace_offset = java_lang_Throwable::hc_static_unassigned_stacktrace_offset *  x;
 
   // java_lang_boxing_object
   java_lang_boxing_object::value_offset = java_lang_boxing_object::hc_value_offset + header;

--- a/src/share/vm/classfile/javaClasses.hpp	Fri Jul 22 23:42:46 2011 -0700
+++ b/src/share/vm/classfile/javaClasses.hpp	Sat Jul 23 10:42:20 2011 -0400
@@ -393,6 +393,9 @@
     hc_cause_offset         =  2,  // New since 1.4
     hc_stackTrace_offset    =  3   // New since 1.4
   };
+  enum {
+      hc_static_unassigned_stacktrace_offset = 0  // New since 1.7
+  };
   // Trace constants
   enum {
     trace_methods_offset = 0,
@@ -406,6 +409,7 @@
   static int detailMessage_offset;
   static int cause_offset;
   static int stackTrace_offset;
+  static int static_unassigned_stacktrace_offset;
 
   // Printing
   static char* print_stack_element_to_buffer(methodOop method, int bci);
@@ -414,6 +418,9 @@
   static void clear_stacktrace(oop throwable);
   // No stack trace available
   static const char* no_stack_trace_message();
+  // Stacktrace (post JDK 1.7.0 to allow immutability protocol to be followed)
+  static void set_stacktrace(oop throwable, oop st_element_array);
+  static oop unassigned_stacktrace();
 
  public:
   // Backtrace
@@ -438,7 +445,6 @@
   static void allocate_backtrace(Handle throwable, TRAPS);
   // Fill in current stack trace for throwable with preallocated backtrace (no GC)
   static void fill_in_stack_trace_of_preallocated_backtrace(Handle throwable);
-
   // Fill in current stack trace, can cause GC
   static void fill_in_stack_trace(Handle throwable, methodHandle method, TRAPS);
   static void fill_in_stack_trace(Handle throwable, methodHandle method = methodHandle());

--- a/src/share/vm/prims/jvmtiTagMap.cpp	Fri Jul 22 23:42:46 2011 -0700
+++ b/src/share/vm/prims/jvmtiTagMap.cpp	Sat Jul 23 10:42:20 2011 -0400
@@ -1647,6 +1647,7 @@
   // saved headers
   static GrowableArray<oop>* _saved_oop_stack;
   static GrowableArray<markOop>* _saved_mark_stack;
+  static bool _needs_reset;                  // do we need to reset mark bits?
 
  public:
   static void init();                       // initialize
@@ -1654,10 +1655,14 @@
 
   static inline void mark(oop o);           // mark an object
   static inline bool visited(oop o);        // check if object has been visited
+
+  static inline bool needs_reset()            { return _needs_reset; }
+  static inline void set_needs_reset(bool v)  { _needs_reset = v; }
 };
 
 GrowableArray<oop>* ObjectMarker::_saved_oop_stack = NULL;
 GrowableArray<markOop>* ObjectMarker::_saved_mark_stack = NULL;
+bool ObjectMarker::_needs_reset = true;  // need to reset mark bits by default
 
 // initialize ObjectMarker - prepares for object marking
 void ObjectMarker::init() {
@@ -1680,7 +1685,13 @@
   // iterate over all objects and restore the mark bits to
   // their initial value
   RestoreMarksClosure blk;
-  Universe::heap()->object_iterate(&blk);
+  if (needs_reset()) {
+    Universe::heap()->object_iterate(&blk);
+  } else {
+    // We don't need to reset mark bits on this call, but reset the
+    // flag to the default for the next call.
+    set_needs_reset(true);
+  }
 
   // When sharing is enabled we need to restore the headers of the objects
   // in the readwrite space too.
@@ -3023,7 +3034,8 @@
 }
 
 
-// collects all simple (non-stack) roots.
+// Collects all simple (non-stack) roots except for threads;
+// threads are handled in collect_stack_roots() as an optimization.
 // if there's a heap root callback provided then the callback is
 // invoked for each simple root.
 // if an object reference callback is provided then all simple
@@ -3054,16 +3066,7 @@
     return false;
   }
 
-  // Threads
-  for (JavaThread* thread = Threads::first(); thread != NULL ; thread = thread->next()) {
-    oop threadObj = thread->threadObj();
-    if (threadObj != NULL && !thread->is_exiting() && !thread->is_hidden_from_external_view()) {
-      bool cont = CallbackInvoker::report_simple_root(JVMTI_HEAP_REFERENCE_THREAD, threadObj);
-      if (!cont) {
-        return false;
-      }
-    }
-  }
+  // threads are now handled in collect_stack_roots()
 
   // Other kinds of roots maintained by HotSpot
   // Many of these won't be visible but others (such as instances of important
@@ -3175,13 +3178,20 @@
 }
 
 
-// collects all stack roots - for each thread it walks the execution
+// Collects the simple roots for all threads and collects all
+// stack roots - for each thread it walks the execution
 // stack to find all references and local JNI refs.
 inline bool VM_HeapWalkOperation::collect_stack_roots() {
   JNILocalRootsClosure blk;
   for (JavaThread* thread = Threads::first(); thread != NULL ; thread = thread->next()) {
     oop threadObj = thread->threadObj();
     if (threadObj != NULL && !thread->is_exiting() && !thread->is_hidden_from_external_view()) {
+      // Collect the simple root for this thread before we
+      // collect its stack roots
+      if (!CallbackInvoker::report_simple_root(JVMTI_HEAP_REFERENCE_THREAD,
+                                               threadObj)) {
+        return false;
+      }
       if (!collect_stack_roots(thread, &blk)) {
         return false;
       }
@@ -3235,8 +3245,20 @@
 
   // the heap walk starts with an initial object or the heap roots
   if (initial_object().is_null()) {
+    // If either collect_stack_roots() or collect_simple_roots()
+    // returns false at this point, then there are no mark bits
+    // to reset.
+    ObjectMarker::set_needs_reset(false);
+
+    // Calling collect_stack_roots() before collect_simple_roots()
+    // can result in a big performance boost for an agent that is
+    // focused on analyzing references in the thread stacks.
+    if (!collect_stack_roots()) return;
+
     if (!collect_simple_roots()) return;
-    if (!collect_stack_roots()) return;
+
+    // no early return so enable heap traversal to reset the mark bits
+    ObjectMarker::set_needs_reset(true);
   } else {
     visit_stack()->push(initial_object()());
   }