--- a/src/share/vm/gc_interface/collectedHeap.hpp	Fri Feb 24 18:30:42 2012 -0800
+++ b/src/share/vm/gc_interface/collectedHeap.hpp	Mon Feb 27 13:10:13 2012 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -31,6 +31,7 @@
 #include "runtime/handles.hpp"
 #include "runtime/perfData.hpp"
 #include "runtime/safepoint.hpp"
+#include "utilities/events.hpp"
 
 // A "CollectedHeap" is an implementation of a java heap for HotSpot.  This
 // is an abstract class: there may be many different kinds of heaps.  This
@@ -43,6 +44,29 @@
 class Thread;
 class CollectorPolicy;
 
+class GCMessage : public FormatBuffer<1024> {
+ public:
+  bool is_before;
+
+ public:
+  GCMessage() {}
+};
+
+class GCHeapLog : public EventLogBase<GCMessage> {
+ private:
+  void log_heap(bool before);
+
+ public:
+  GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
+
+  void log_heap_before() {
+    log_heap(true);
+  }
+  void log_heap_after() {
+    log_heap(false);
+  }
+};
+
 //
 // CollectedHeap
 //   SharedHeap
@@ -62,6 +86,8 @@
   // Used for filler objects (static, but initialized in ctor).
   static size_t _filler_array_max_size;
 
+  GCHeapLog* _gc_heap_log;
+
   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
   bool _defer_initial_card_mark;
 
@@ -69,7 +95,7 @@
   MemRegion _reserved;
   BarrierSet* _barrier_set;
   bool _is_gc_active;
-  int _n_par_threads;
+  uint _n_par_threads;
 
   unsigned int _total_collections;          // ... started
   unsigned int _total_full_collections;     // ... started
@@ -217,8 +243,8 @@
     return p == NULL || is_in_reserved(p);
   }
 
-  // Returns "TRUE" if "p" points to the head of an allocated object in the
-  // heap. Since this method can be expensive in general, we restrict its
+  // Returns "TRUE" iff "p" points into the committed areas of the heap.
+  // Since this method can be expensive in general, we restrict its
   // use to assertion checking only.
   virtual bool is_in(const void* p) const = 0;
 
@@ -309,10 +335,10 @@
   GCCause::Cause gc_cause() { return _gc_cause; }
 
   // Number of threads currently working on GC tasks.
-  int n_par_threads() { return _n_par_threads; }
+  uint n_par_threads() { return _n_par_threads; }
 
   // May be overridden to set additional parallelism.
-  virtual void set_par_threads(int t) { _n_par_threads = t; };
+  virtual void set_par_threads(uint t) { _n_par_threads = t; };
 
   // Preload classes into the shared portion of the heap, and then dump
   // that data to a file so that it can be loaded directly by another
@@ -618,6 +644,27 @@
   // Default implementation does nothing.
   virtual void print_tracing_info() const = 0;
 
+  // If PrintHeapAtGC is set call the appropriate routi
+  void print_heap_before_gc() {
+    if (PrintHeapAtGC) {
+      Universe::print_heap_before_gc();
+    }
+    if (_gc_heap_log != NULL) {
+      _gc_heap_log->log_heap_before();
+    }
+  }
+  void print_heap_after_gc() {
+    if (PrintHeapAtGC) {
+      Universe::print_heap_after_gc();
+    }
+    if (_gc_heap_log != NULL) {
+      _gc_heap_log->log_heap_after();
+    }
+  }
+
+  // Allocate GCHeapLog during VM startup
+  static void initialize_heap_log();
+
   // Heap verification
   virtual void verify(bool allow_dirty, bool silent, VerifyOption option) = 0;
 
@@ -648,6 +695,10 @@
   // reduce the occurrence of ParallelGCThreads to uses where the
   // actual number may be germane.
   static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
+
+  /////////////// Unit tests ///////////////
+
+  NOT_PRODUCT(static void test_is_in();)
 };
 
 // Class to set and reset the GC cause for a CollectedHeap.