--- a/src/os/linux/vm/os_linux.cpp	Fri Mar 16 15:13:22 2012 -0400
+++ b/src/os/linux/vm/os_linux.cpp	Fri Mar 16 23:45:05 2012 -0700
@@ -2547,7 +2547,14 @@
 }
 
 void os::free_memory(char *addr, size_t bytes, size_t alignment_hint) {
-  commit_memory(addr, bytes, alignment_hint, false);
+  // This method works by doing an mmap over an existing mmaping and effectively discarding
+  // the existing pages. However it won't work for SHM-based large pages that cannot be
+  // uncommitted at all. We don't do anything in this case to avoid creating a segment with
+  // small pages on top of the SHM segment. This method always works for small pages, so we
+  // allow that in any case.
+  if (alignment_hint <= (size_t)os::vm_page_size() || !UseSHM) {
+    commit_memory(addr, bytes, alignment_hint, false);
+  }
 }
 
 void os::numa_make_global(char *addr, size_t bytes) {

--- a/src/share/vm/gc_implementation/g1/survRateGroup.cpp	Fri Mar 16 15:13:22 2012 -0400
+++ b/src/share/vm/gc_implementation/g1/survRateGroup.cpp	Fri Mar 16 23:45:05 2012 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2010, 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
@@ -38,33 +38,36 @@
     _summary_surv_rates(NULL),
     _surv_rate(NULL),
     _accum_surv_rate_pred(NULL),
-    _surv_rate_pred(NULL)
-{
+    _surv_rate_pred(NULL),
+    _stats_arrays_length(0) {
   reset();
   if (summary_surv_rates_len > 0) {
     size_t length = summary_surv_rates_len;
-      _summary_surv_rates = NEW_C_HEAP_ARRAY(NumberSeq*, length);
-    if (_summary_surv_rates == NULL) {
-      vm_exit_out_of_memory(sizeof(NumberSeq*) * length,
-                            "Not enough space for surv rate summary");
+    _summary_surv_rates = NEW_C_HEAP_ARRAY(NumberSeq*, length);
+    for (size_t i = 0; i < length; ++i) {
+      _summary_surv_rates[i] = new NumberSeq();
     }
-    for (size_t i = 0; i < length; ++i)
-      _summary_surv_rates[i] = new NumberSeq();
   }
 
   start_adding_regions();
 }
 
-
-void SurvRateGroup::reset()
-{
+void SurvRateGroup::reset() {
   _all_regions_allocated = 0;
   _setup_seq_num         = 0;
-  _stats_arrays_length   = 0;
   _accum_surv_rate       = 0.0;
   _last_pred             = 0.0;
   // the following will set up the arrays with length 1
   _region_num            = 1;
+
+  // The call to stop_adding_regions() will use "new" to refill
+  // the _surv_rate_pred array, so we need to make sure to call
+  // "delete".
+  for (size_t i = 0; i < _stats_arrays_length; ++i) {
+    delete _surv_rate_pred[i];
+  }
+  _stats_arrays_length = 0;
+
   stop_adding_regions();
   guarantee( _stats_arrays_length == 1, "invariant" );
   guarantee( _surv_rate_pred[0] != NULL, "invariant" );
@@ -73,72 +76,47 @@
   _region_num = 0;
 }
 
-
 void
 SurvRateGroup::start_adding_regions() {
   _setup_seq_num   = _stats_arrays_length;
   _region_num      = 0;
   _accum_surv_rate = 0.0;
-
-#if 0
-  gclog_or_tty->print_cr("[%s] start adding regions, seq num %d, length %d",
-                         _name, _setup_seq_num, _region_num);
-#endif // 0
 }
 
 void
 SurvRateGroup::stop_adding_regions() {
-
-#if 0
-  gclog_or_tty->print_cr("[%s] stop adding regions, length %d", _name, _region_num);
-#endif // 0
-
   if (_region_num > _stats_arrays_length) {
     double* old_surv_rate = _surv_rate;
     double* old_accum_surv_rate_pred = _accum_surv_rate_pred;
     TruncatedSeq** old_surv_rate_pred = _surv_rate_pred;
 
     _surv_rate = NEW_C_HEAP_ARRAY(double, _region_num);
-    if (_surv_rate == NULL) {
-      vm_exit_out_of_memory(sizeof(double) * _region_num,
-                            "Not enough space for surv rate array.");
-    }
     _accum_surv_rate_pred = NEW_C_HEAP_ARRAY(double, _region_num);
-    if (_accum_surv_rate_pred == NULL) {
-      vm_exit_out_of_memory(sizeof(double) * _region_num,
-                         "Not enough space for accum surv rate pred array.");
-    }
     _surv_rate_pred = NEW_C_HEAP_ARRAY(TruncatedSeq*, _region_num);
-    if (_surv_rate == NULL) {
-      vm_exit_out_of_memory(sizeof(TruncatedSeq*) * _region_num,
-                            "Not enough space for surv rate pred array.");
-    }
 
-    for (size_t i = 0; i < _stats_arrays_length; ++i)
+    for (size_t i = 0; i < _stats_arrays_length; ++i) {
       _surv_rate_pred[i] = old_surv_rate_pred[i];
-
-#if 0
-    gclog_or_tty->print_cr("[%s] stop adding regions, new seqs %d to %d",
-                  _name, _array_length, _region_num - 1);
-#endif // 0
-
+    }
     for (size_t i = _stats_arrays_length; i < _region_num; ++i) {
       _surv_rate_pred[i] = new TruncatedSeq(10);
-      // _surv_rate_pred[i]->add(last_pred);
     }
 
     _stats_arrays_length = _region_num;
 
-    if (old_surv_rate != NULL)
+    if (old_surv_rate != NULL) {
       FREE_C_HEAP_ARRAY(double, old_surv_rate);
-    if (old_accum_surv_rate_pred != NULL)
+    }
+    if (old_accum_surv_rate_pred != NULL) {
       FREE_C_HEAP_ARRAY(double, old_accum_surv_rate_pred);
-    if (old_surv_rate_pred != NULL)
-      FREE_C_HEAP_ARRAY(NumberSeq*, old_surv_rate_pred);
+    }
+    if (old_surv_rate_pred != NULL) {
+      FREE_C_HEAP_ARRAY(TruncatedSeq*, old_surv_rate_pred);
+    }
   }
 
-  for (size_t i = 0; i < _stats_arrays_length; ++i)
+  for (size_t i = 0; i < _stats_arrays_length; ++i) {
     _surv_rate[i] = 0.0;
+  }
 }
 
 double
@@ -187,12 +165,6 @@
 SurvRateGroup::all_surviving_words_recorded(bool propagate) {
   if (propagate && _region_num > 0) { // conservative
     double surv_rate = _surv_rate_pred[_region_num-1]->last();
-
-#if 0
-    gclog_or_tty->print_cr("propagating %1.2lf from %d to %d",
-                  surv_rate, _curr_length, _array_length - 1);
-#endif // 0
-
     for (size_t i = _region_num; i < _stats_arrays_length; ++i) {
       guarantee( _surv_rate[i] <= 0.00001,
                  "the slot should not have been updated" );

--- a/src/share/vm/memory/cardTableModRefBS.hpp	Fri Mar 16 15:13:22 2012 -0400
+++ b/src/share/vm/memory/cardTableModRefBS.hpp	Fri Mar 16 23:45:05 2012 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 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
@@ -72,6 +72,9 @@
     CT_MR_BS_last_reserved      = 16
   };
 
+  // a word's worth (row) of clean card values
+  static const intptr_t clean_card_row = (intptr_t)(-1);
+
   // dirty and precleaned are equivalent wrt younger_refs_iter.
   static bool card_is_dirty_wrt_gen_iter(jbyte cv) {
     return cv == dirty_card || cv == precleaned_card;

--- a/src/share/vm/memory/cardTableRS.cpp	Fri Mar 16 15:13:22 2012 -0400
+++ b/src/share/vm/memory/cardTableRS.cpp	Fri Mar 16 23:45:05 2012 -0700
@@ -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
@@ -173,6 +173,10 @@
             SharedHeap::heap()->workers()->active_workers()), "Mismatch");
 }
 
+bool ClearNoncleanCardWrapper::is_word_aligned(jbyte* entry) {
+  return (((intptr_t)entry) & (BytesPerWord-1)) == 0;
+}
+
 void ClearNoncleanCardWrapper::do_MemRegion(MemRegion mr) {
   assert(mr.word_size() > 0, "Error");
   assert(_ct->is_aligned(mr.start()), "mr.start() should be card aligned");
@@ -194,6 +198,17 @@
         const MemRegion mrd(start_of_non_clean, end_of_non_clean);
         _dirty_card_closure->do_MemRegion(mrd);
       }
+
+      // fast forward through potential continuous whole-word range of clean cards beginning at a word-boundary
+      if (is_word_aligned(cur_entry)) {
+        jbyte* cur_row = cur_entry - BytesPerWord;
+        while (cur_row >= limit && *((intptr_t*)cur_row) ==  CardTableRS::clean_card_row()) {
+          cur_row -= BytesPerWord;
+        }
+        cur_entry = cur_row + BytesPerWord;
+        cur_hw = _ct->addr_for(cur_entry);
+      }
+
       // Reset the dirty window, while continuing to look
       // for the next dirty card that will start a
       // new dirty window.

--- a/src/share/vm/memory/cardTableRS.hpp	Fri Mar 16 15:13:22 2012 -0400
+++ b/src/share/vm/memory/cardTableRS.hpp	Fri Mar 16 23:45:05 2012 -0700
@@ -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
@@ -45,6 +45,10 @@
     return CardTableModRefBS::clean_card;
   }
 
+  static intptr_t clean_card_row() {
+    return CardTableModRefBS::clean_card_row;
+  }
+
   static bool
   card_is_dirty_wrt_gen_iter(jbyte cv) {
     return CardTableModRefBS::card_is_dirty_wrt_gen_iter(cv);
@@ -176,6 +180,8 @@
   // Work methods called by the clear_card()
   inline bool clear_card_serial(jbyte* entry);
   inline bool clear_card_parallel(jbyte* entry);
+  // check alignment of pointer
+  bool is_word_aligned(jbyte* entry);
 
 public:
   ClearNoncleanCardWrapper(DirtyCardToOopClosure* dirty_card_closure, CardTableRS* ct);

--- a/src/share/vm/utilities/numberSeq.cpp	Fri Mar 16 15:13:22 2012 -0400
+++ b/src/share/vm/utilities/numberSeq.cpp	Fri Mar 16 23:45:05 2012 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2010, 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
@@ -156,6 +156,10 @@
     _sequence[i] = 0.0;
 }
 
+TruncatedSeq::~TruncatedSeq() {
+  FREE_C_HEAP_ARRAY(double, _sequence);
+}
+
 void TruncatedSeq::add(double val) {
   AbsSeq::add(val);
 

--- a/src/share/vm/utilities/numberSeq.hpp	Fri Mar 16 15:13:22 2012 -0400
+++ b/src/share/vm/utilities/numberSeq.hpp	Fri Mar 16 23:45:05 2012 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2010, 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
@@ -118,6 +118,7 @@
   // accepts a value for L
   TruncatedSeq(int length = DefaultSeqLength,
                double alpha = DEFAULT_ALPHA_VALUE);
+  ~TruncatedSeq();
   virtual void add(double val);
   virtual double maximum() const;
   virtual double last() const; // the last value added to the sequence