--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Fri Jun 10 13:16:40 2011 -0400
@@ -578,16 +578,16 @@
   }
   if (res == NULL && do_expand) {
     if (expand(word_size * HeapWordSize)) {
-      // The expansion succeeded and so we should have at least one
-      // region on the free list.
-      res = _free_list.remove_head();
+      // Even though the heap was expanded, it might not have reached
+      // the desired size. So, we cannot assume that the allocation
+      // will succeed.
+      res = _free_list.remove_head_or_null();
     }
   }
   if (res != NULL) {
     if (G1PrintHeapRegions) {
-      gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT","PTR_FORMAT"], "
-                             "top "PTR_FORMAT, res->hrs_index(),
-                             res->bottom(), res->end(), res->top());
+      gclog_or_tty->print_cr("new alloc region "HR_FORMAT,
+                             HR_FORMAT_PARAMS(res));
     }
   }
   return res;
@@ -608,12 +608,12 @@
   return alloc_region;
 }
 
-int G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
-                                                       size_t word_size) {
+size_t G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
+                                                          size_t word_size) {
   assert(isHumongous(word_size), "word_size should be humongous");
   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 
-  int first = -1;
+  size_t first = G1_NULL_HRS_INDEX;
   if (num_regions == 1) {
     // Only one region to allocate, no need to go through the slower
     // path. The caller will attempt the expasion if this fails, so
@@ -622,7 +622,7 @@
     if (hr != NULL) {
       first = hr->hrs_index();
     } else {
-      first = -1;
+      first = G1_NULL_HRS_INDEX;
     }
   } else {
     // We can't allocate humongous regions while cleanupComplete() is
@@ -637,10 +637,10 @@
     append_secondary_free_list_if_not_empty_with_lock();
 
     if (free_regions() >= num_regions) {
-      first = _hrs->find_contiguous(num_regions);
-      if (first != -1) {
-        for (int i = first; i < first + (int) num_regions; ++i) {
-          HeapRegion* hr = _hrs->at(i);
+      first = _hrs.find_contiguous(num_regions);
+      if (first != G1_NULL_HRS_INDEX) {
+        for (size_t i = first; i < first + num_regions; ++i) {
+          HeapRegion* hr = region_at(i);
           assert(hr->is_empty(), "sanity");
           assert(is_on_master_free_list(hr), "sanity");
           hr->set_pending_removal(true);
@@ -653,15 +653,15 @@
 }
 
 HeapWord*
-G1CollectedHeap::humongous_obj_allocate_initialize_regions(int first,
+G1CollectedHeap::humongous_obj_allocate_initialize_regions(size_t first,
                                                            size_t num_regions,
                                                            size_t word_size) {
-  assert(first != -1, "pre-condition");
+  assert(first != G1_NULL_HRS_INDEX, "pre-condition");
   assert(isHumongous(word_size), "word_size should be humongous");
   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 
   // Index of last region in the series + 1.
-  int last = first + (int) num_regions;
+  size_t last = first + num_regions;
 
   // We need to initialize the region(s) we just discovered. This is
   // a bit tricky given that it can happen concurrently with
@@ -676,7 +676,7 @@
   assert(word_size <= word_size_sum, "sanity");
 
   // This will be the "starts humongous" region.
-  HeapRegion* first_hr = _hrs->at(first);
+  HeapRegion* first_hr = region_at(first);
   // The header of the new object will be placed at the bottom of
   // the first region.
   HeapWord* new_obj = first_hr->bottom();
@@ -711,8 +711,8 @@
   // Then, if there are any, we will set up the "continues
   // humongous" regions.
   HeapRegion* hr = NULL;
-  for (int i = first + 1; i < last; ++i) {
-    hr = _hrs->at(i);
+  for (size_t i = first + 1; i < last; ++i) {
+    hr = region_at(i);
     hr->set_continuesHumongous(first_hr);
   }
   // If we have "continues humongous" regions (hr != NULL), then the
@@ -746,8 +746,8 @@
   // last one) is actually used when we will free up the humongous
   // region in free_humongous_region().
   hr = NULL;
-  for (int i = first + 1; i < last; ++i) {
-    hr = _hrs->at(i);
+  for (size_t i = first + 1; i < last; ++i) {
+    hr = region_at(i);
     if ((i + 1) == last) {
       // last continues humongous region
       assert(hr->bottom() < new_top && new_top <= hr->end(),
@@ -783,9 +783,9 @@
   size_t num_regions =
          round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
   size_t x_size = expansion_regions();
-  size_t fs = _hrs->free_suffix();
-  int first = humongous_obj_allocate_find_first(num_regions, word_size);
-  if (first == -1) {
+  size_t fs = _hrs.free_suffix();
+  size_t first = humongous_obj_allocate_find_first(num_regions, word_size);
+  if (first == G1_NULL_HRS_INDEX) {
     // The only thing we can do now is attempt expansion.
     if (fs + x_size >= num_regions) {
       // If the number of regions we're trying to allocate for this
@@ -799,16 +799,16 @@
       assert(num_regions > fs, "earlier allocation should have succeeded");
 
       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
+        // Even though the heap was expanded, it might not have
+        // reached the desired size. So, we cannot assume that the
+        // allocation will succeed.
         first = humongous_obj_allocate_find_first(num_regions, word_size);
-        // If the expansion was successful then the allocation
-        // should have been successful.
-        assert(first != -1, "this should have worked");
       }
     }
   }
 
   HeapWord* result = NULL;
-  if (first != -1) {
+  if (first != G1_NULL_HRS_INDEX) {
     result =
       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
     assert(result != NULL, "it should always return a valid result");
@@ -1366,6 +1366,7 @@
   // Update the number of full collections that have been completed.
   increment_full_collections_completed(false /* concurrent */);
 
+  _hrs.verify_optional();
   verify_region_sets_optional();
 
   if (PrintHeapAtGC) {
@@ -1589,6 +1590,7 @@
 
   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
   if (expand(expand_bytes)) {
+    _hrs.verify_optional();
     verify_region_sets_optional();
     return attempt_allocation_at_safepoint(word_size,
                                  false /* expect_null_mutator_alloc_region */);
@@ -1596,6 +1598,19 @@
   return NULL;
 }
 
+void G1CollectedHeap::update_committed_space(HeapWord* old_end,
+                                             HeapWord* new_end) {
+  assert(old_end != new_end, "don't call this otherwise");
+  assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
+
+  // Update the committed mem region.
+  _g1_committed.set_end(new_end);
+  // Tell the card table about the update.
+  Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
+  // Tell the BOT about the update.
+  _bot_shared->resize(_g1_committed.word_size());
+}
+
 bool G1CollectedHeap::expand(size_t expand_bytes) {
   size_t old_mem_size = _g1_storage.committed_size();
   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
@@ -1607,47 +1622,37 @@
                            old_mem_size/K, aligned_expand_bytes/K);
   }
 
-  HeapWord* old_end = (HeapWord*)_g1_storage.high();
+  // First commit the memory.
+  HeapWord* old_end = (HeapWord*) _g1_storage.high();
   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
   if (successful) {
-    HeapWord* new_end = (HeapWord*)_g1_storage.high();
-
-    // Expand the committed region.
-    _g1_committed.set_end(new_end);
-
-    // Tell the cardtable about the expansion.
-    Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
-
-    // And the offset table as well.
-    _bot_shared->resize(_g1_committed.word_size());
-
-    expand_bytes = aligned_expand_bytes;
-    HeapWord* base = old_end;
-
-    // Create the heap regions for [old_end, new_end)
-    while (expand_bytes > 0) {
-      HeapWord* high = base + HeapRegion::GrainWords;
-
-      // Create a new HeapRegion.
-      MemRegion mr(base, high);
-      bool is_zeroed = !_g1_max_committed.contains(base);
-      HeapRegion* hr = new HeapRegion(_bot_shared, mr, is_zeroed);
-
-      // Add it to the HeapRegionSeq.
-      _hrs->insert(hr);
-      _free_list.add_as_tail(hr);
-
-      // And we used up an expansion region to create it.
-      _expansion_regions--;
-
-      expand_bytes -= HeapRegion::GrainBytes;
-      base += HeapRegion::GrainWords;
+    // Then propagate this update to the necessary data structures.
+    HeapWord* new_end = (HeapWord*) _g1_storage.high();
+    update_committed_space(old_end, new_end);
+
+    FreeRegionList expansion_list("Local Expansion List");
+    MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
+    assert(mr.start() == old_end, "post-condition");
+    // mr might be a smaller region than what was requested if
+    // expand_by() was unable to allocate the HeapRegion instances
+    assert(mr.end() <= new_end, "post-condition");
+
+    size_t actual_expand_bytes = mr.byte_size();
+    assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
+    assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
+           "post-condition");
+    if (actual_expand_bytes < aligned_expand_bytes) {
+      // We could not expand _hrs to the desired size. In this case we
+      // need to shrink the committed space accordingly.
+      assert(mr.end() < new_end, "invariant");
+
+      size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
+      // First uncommit the memory.
+      _g1_storage.shrink_by(diff_bytes);
+      // Then propagate this update to the necessary data structures.
+      update_committed_space(new_end, mr.end());
     }
-    assert(base == new_end, "sanity");
-
-    // Now update max_committed if necessary.
-    _g1_max_committed.set_end(MAX2(_g1_max_committed.end(), new_end));
-
+    _free_list.add_as_tail(&expansion_list);
   } else {
     // The expansion of the virtual storage space was unsuccessful.
     // Let's see if it was because we ran out of swap.
@@ -1667,37 +1672,31 @@
   return successful;
 }
 
-void G1CollectedHeap::shrink_helper(size_t shrink_bytes)
-{
+void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
   size_t old_mem_size = _g1_storage.committed_size();
   size_t aligned_shrink_bytes =
     ReservedSpace::page_align_size_down(shrink_bytes);
   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
                                          HeapRegion::GrainBytes);
   size_t num_regions_deleted = 0;
-  MemRegion mr = _hrs->shrink_by(aligned_shrink_bytes, num_regions_deleted);
-
-  assert(mr.end() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
-  if (mr.byte_size() > 0)
+  MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
+  HeapWord* old_end = (HeapWord*) _g1_storage.high();
+  assert(mr.end() == old_end, "post-condition");
+  if (mr.byte_size() > 0) {
     _g1_storage.shrink_by(mr.byte_size());
-  assert(mr.start() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
-
-  _g1_committed.set_end(mr.start());
-  _expansion_regions += num_regions_deleted;
-
-  // Tell the cardtable about it.
-  Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
-
-  // And the offset table as well.
-  _bot_shared->resize(_g1_committed.word_size());
-
-  HeapRegionRemSet::shrink_heap(n_regions());
-
-  if (Verbose && PrintGC) {
-    size_t new_mem_size = _g1_storage.committed_size();
-    gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
-                           old_mem_size/K, aligned_shrink_bytes/K,
-                           new_mem_size/K);
+    HeapWord* new_end = (HeapWord*) _g1_storage.high();
+    assert(mr.start() == new_end, "post-condition");
+
+    _expansion_regions += num_regions_deleted;
+    update_committed_space(old_end, new_end);
+    HeapRegionRemSet::shrink_heap(n_regions());
+
+    if (Verbose && PrintGC) {
+      size_t new_mem_size = _g1_storage.committed_size();
+      gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
+                             old_mem_size/K, aligned_shrink_bytes/K,
+                             new_mem_size/K);
+    }
   }
 }
 
@@ -1712,6 +1711,7 @@
   shrink_helper(shrink_bytes);
   rebuild_region_lists();
 
+  _hrs.verify_optional();
   verify_region_sets_optional();
 }
 
@@ -1890,9 +1890,9 @@
 
   _g1_storage.initialize(g1_rs, 0);
   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
-  _g1_max_committed = _g1_committed;
-  _hrs = new HeapRegionSeq(_expansion_regions);
-  guarantee(_hrs != NULL, "Couldn't allocate HeapRegionSeq");
+  _hrs.initialize((HeapWord*) _g1_reserved.start(),
+                  (HeapWord*) _g1_reserved.end(),
+                  _expansion_regions);
 
   // 6843694 - ensure that the maximum region index can fit
   // in the remembered set structures.
@@ -1991,8 +1991,9 @@
   // Here we allocate the dummy full region that is required by the
   // G1AllocRegion class. If we don't pass an address in the reserved
   // space here, lots of asserts fire.
-  MemRegion mr(_g1_reserved.start(), HeapRegion::GrainWords);
-  HeapRegion* dummy_region = new HeapRegion(_bot_shared, mr, true);
+
+  HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
+                                             _g1_reserved.start());
   // We'll re-use the same region whether the alloc region will
   // require BOT updates or not and, if it doesn't, then a non-young
   // region will complain that it cannot support allocations without
@@ -2100,7 +2101,7 @@
 
 size_t G1CollectedHeap::recalculate_used() const {
   SumUsedClosure blk;
-  _hrs->iterate(&blk);
+  heap_region_iterate(&blk);
   return blk.result();
 }
 
@@ -2120,7 +2121,7 @@
 
 size_t G1CollectedHeap::recalculate_used_regions() const {
   SumUsedRegionsClosure blk;
-  _hrs->iterate(&blk);
+  heap_region_iterate(&blk);
   return blk.result();
 }
 #endif // PRODUCT
@@ -2285,8 +2286,8 @@
 }
 
 bool G1CollectedHeap::is_in(const void* p) const {
-  if (_g1_committed.contains(p)) {
-    HeapRegion* hr = _hrs->addr_to_region(p);
+  HeapRegion* hr = _hrs.addr_to_region((HeapWord*) p);
+  if (hr != NULL) {
     return hr->is_in(p);
   } else {
     return _perm_gen->as_gen()->is_in(p);
@@ -2314,7 +2315,7 @@
 
 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
   IterateOopClosureRegionClosure blk(_g1_committed, cl);
-  _hrs->iterate(&blk);
+  heap_region_iterate(&blk);
   if (do_perm) {
     perm_gen()->oop_iterate(cl);
   }
@@ -2322,7 +2323,7 @@
 
 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
   IterateOopClosureRegionClosure blk(mr, cl);
-  _hrs->iterate(&blk);
+  heap_region_iterate(&blk);
   if (do_perm) {
     perm_gen()->oop_iterate(cl);
   }
@@ -2344,7 +2345,7 @@
 
 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
   IterateObjectClosureRegionClosure blk(cl);
-  _hrs->iterate(&blk);
+  heap_region_iterate(&blk);
   if (do_perm) {
     perm_gen()->object_iterate(cl);
   }
@@ -2369,26 +2370,19 @@
 
 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
   SpaceClosureRegionClosure blk(cl);
-  _hrs->iterate(&blk);
+  heap_region_iterate(&blk);
 }
 
-void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) {
-  _hrs->iterate(cl);
+void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
+  _hrs.iterate(cl);
 }
 
 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
-                                               HeapRegionClosure* cl) {
-  _hrs->iterate_from(r, cl);
+                                               HeapRegionClosure* cl) const {
+  _hrs.iterate_from(r, cl);
 }
 
 void
-G1CollectedHeap::heap_region_iterate_from(int idx, HeapRegionClosure* cl) {
-  _hrs->iterate_from(idx, cl);
-}
-
-HeapRegion* G1CollectedHeap::region_at(size_t idx) { return _hrs->at(idx); }
-
-void
 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
                                                  int worker,
                                                  jint claim_value) {
@@ -2568,7 +2562,7 @@
 }
 
 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
-  return _hrs->length() > 0 ? _hrs->at(0) : NULL;
+  return n_regions() > 0 ? region_at(0) : NULL;
 }
 
 
@@ -2881,7 +2875,7 @@
              "sanity check");
     } else {
       VerifyRegionClosure blk(allow_dirty, false, use_prev_marking);
-      _hrs->iterate(&blk);
+      heap_region_iterate(&blk);
       if (blk.failures()) {
         failures = true;
       }
@@ -2950,7 +2944,7 @@
 
 void G1CollectedHeap::print_on_extended(outputStream* st) const {
   PrintRegionClosure blk(st);
-  _hrs->iterate(&blk);
+  heap_region_iterate(&blk);
 }
 
 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
@@ -2989,15 +2983,6 @@
   SpecializationStats::print();
 }
 
-int G1CollectedHeap::addr_to_arena_id(void* addr) const {
-  HeapRegion* hr = heap_region_containing(addr);
-  if (hr == NULL) {
-    return 0;
-  } else {
-    return 1;
-  }
-}
-
 G1CollectedHeap* G1CollectedHeap::heap() {
   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
          "not a garbage-first heap");
@@ -3477,6 +3462,7 @@
     }
   }
 
+  _hrs.verify_optional();
   verify_region_sets_optional();
 
   TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
@@ -3609,8 +3595,8 @@
 public:
   bool doHeapRegion(HeapRegion* r) {
     if (r->is_gc_alloc_region()) {
-      gclog_or_tty->print_cr("Region %d ["PTR_FORMAT"...] is still a gc_alloc_region.",
-                             r->hrs_index(), r->bottom());
+      gclog_or_tty->print_cr("Region "HR_FORMAT" is still a GC alloc region",
+                             HR_FORMAT_PARAMS(r));
     }
     return false;
   }
@@ -3695,9 +3681,8 @@
       // the region was retained from the last collection
       ++_gc_alloc_region_counts[ap];
       if (G1PrintHeapRegions) {
-        gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT", "PTR_FORMAT"], "
-                               "top "PTR_FORMAT,
-                               alloc_region->hrs_index(), alloc_region->bottom(), alloc_region->end(), alloc_region->top());
+        gclog_or_tty->print_cr("new alloc region "HR_FORMAT,
+                               HR_FORMAT_PARAMS(alloc_region));
       }
     }
 
@@ -4908,10 +4893,10 @@
   hr->set_notHumongous();
   free_region(hr, &hr_pre_used, free_list, par);
 
-  int i = hr->hrs_index() + 1;
+  size_t i = hr->hrs_index() + 1;
   size_t num = 1;
-  while ((size_t) i < n_regions()) {
-    HeapRegion* curr_hr = _hrs->at(i);
+  while (i < n_regions()) {
+    HeapRegion* curr_hr = region_at(i);
     if (!curr_hr->continuesHumongous()) {
       break;
     }
@@ -5271,16 +5256,6 @@
   }
 }
 
-size_t G1CollectedHeap::n_regions() {
-  return _hrs->length();
-}
-
-size_t G1CollectedHeap::max_regions() {
-  return
-    (size_t)align_size_up(max_capacity(), HeapRegion::GrainBytes) /
-    HeapRegion::GrainBytes;
-}
-
 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
   assert(heap_lock_held_for_gc(),
               "the heap lock should already be held by or for this thread");
@@ -5477,6 +5452,15 @@
   }
 };
 
+HeapRegion* G1CollectedHeap::new_heap_region(size_t hrs_index,
+                                             HeapWord* bottom) {
+  HeapWord* end = bottom + HeapRegion::GrainWords;
+  MemRegion mr(bottom, end);
+  assert(_g1_reserved.contains(mr), "invariant");
+  // This might return NULL if the allocation fails
+  return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
+}
+
 void G1CollectedHeap::verify_region_sets() {
   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Fri Jun 10 13:16:40 2011 -0400
@@ -29,6 +29,7 @@
 #include "gc_implementation/g1/g1AllocRegion.hpp"
 #include "gc_implementation/g1/g1RemSet.hpp"
 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
+#include "gc_implementation/g1/heapRegionSeq.hpp"
 #include "gc_implementation/g1/heapRegionSets.hpp"
 #include "gc_implementation/shared/hSpaceCounters.hpp"
 #include "gc_implementation/parNew/parGCAllocBuffer.hpp"
@@ -42,7 +43,6 @@
 // heap subsets that will yield large amounts of garbage.
 
 class HeapRegion;
-class HeapRegionSeq;
 class HRRSCleanupTask;
 class PermanentGenerationSpec;
 class GenerationSpec;
@@ -196,9 +196,6 @@
   // The part of _g1_storage that is currently committed.
   MemRegion _g1_committed;
 
-  // The maximum part of _g1_storage that has ever been committed.
-  MemRegion _g1_max_committed;
-
   // The master free list. It will satisfy all new region allocations.
   MasterFreeRegionList      _free_list;
 
@@ -222,7 +219,7 @@
   void rebuild_region_lists();
 
   // The sequence of all heap regions in the heap.
-  HeapRegionSeq* _hrs;
+  HeapRegionSeq _hrs;
 
   // Alloc region used to satisfy mutator allocation requests.
   MutatorAllocRegion _mutator_alloc_region;
@@ -421,13 +418,15 @@
   // Attempt to satisfy a humongous allocation request of the given
   // size by finding a contiguous set of free regions of num_regions
   // length and remove them from the master free list. Return the
-  // index of the first region or -1 if the search was unsuccessful.
-  int humongous_obj_allocate_find_first(size_t num_regions, size_t word_size);
+  // index of the first region or G1_NULL_HRS_INDEX if the search
+  // was unsuccessful.
+  size_t humongous_obj_allocate_find_first(size_t num_regions,
+                                           size_t word_size);
 
   // Initialize a contiguous set of free regions of length num_regions
   // and starting at index first so that they appear as a single
   // humongous region.
-  HeapWord* humongous_obj_allocate_initialize_regions(int first,
+  HeapWord* humongous_obj_allocate_initialize_regions(size_t first,
                                                       size_t num_regions,
                                                       size_t word_size);
 
@@ -587,8 +586,8 @@
   void register_region_with_in_cset_fast_test(HeapRegion* r) {
     assert(_in_cset_fast_test_base != NULL, "sanity");
     assert(r->in_collection_set(), "invariant");
-    int index = r->hrs_index();
-    assert(0 <= index && (size_t) index < _in_cset_fast_test_length, "invariant");
+    size_t index = r->hrs_index();
+    assert(index < _in_cset_fast_test_length, "invariant");
     assert(!_in_cset_fast_test_base[index], "invariant");
     _in_cset_fast_test_base[index] = true;
   }
@@ -754,6 +753,11 @@
                              HumongousRegionSet* humongous_proxy_set,
                              bool par);
 
+  // Notifies all the necessary spaces that the committed space has
+  // been updated (either expanded or shrunk). It should be called
+  // after _g1_storage is updated.
+  void update_committed_space(HeapWord* old_end, HeapWord* new_end);
+
   // The concurrent marker (and the thread it runs in.)
   ConcurrentMark* _cm;
   ConcurrentMarkThread* _cmThread;
@@ -816,7 +820,6 @@
   oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
   void handle_evacuation_failure_common(oop obj, markOop m);
 
-
   // Ensure that the relevant gc_alloc regions are set.
   void get_gc_alloc_regions();
   // We're done with GC alloc regions. We are going to tear down the
@@ -967,15 +970,13 @@
   }
 
   // The total number of regions in the heap.
-  size_t n_regions();
+  size_t n_regions() { return _hrs.length(); }
+
+  // The max number of regions in the heap.
+  size_t max_regions() { return _hrs.max_length(); }
 
   // The number of regions that are completely free.
-  size_t max_regions();
-
-  // The number of regions that are completely free.
-  size_t free_regions() {
-    return _free_list.length();
-  }
+  size_t free_regions() { return _free_list.length(); }
 
   // The number of regions that are not completely free.
   size_t used_regions() { return n_regions() - free_regions(); }
@@ -983,6 +984,10 @@
   // The number of regions available for "regular" expansion.
   size_t expansion_regions() { return _expansion_regions; }
 
+  // Factory method for HeapRegion instances. It will return NULL if
+  // the allocation fails.
+  HeapRegion* new_heap_region(size_t hrs_index, HeapWord* bottom);
+
   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
@@ -1144,17 +1149,15 @@
 
   // Iterate over heap regions, in address order, terminating the
   // iteration early if the "doHeapRegion" method returns "true".
-  void heap_region_iterate(HeapRegionClosure* blk);
+  void heap_region_iterate(HeapRegionClosure* blk) const;
 
   // Iterate over heap regions starting with r (or the first region if "r"
   // is NULL), in address order, terminating early if the "doHeapRegion"
   // method returns "true".
-  void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk);
+  void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk) const;
 
-  // As above but starting from the region at index idx.
-  void heap_region_iterate_from(int idx, HeapRegionClosure* blk);
-
-  HeapRegion* region_at(size_t idx);
+  // Return the region with the given index. It assumes the index is valid.
+  HeapRegion* region_at(size_t index) const { return _hrs.at(index); }
 
   // Divide the heap region sequence into "chunks" of some size (the number
   // of regions divided by the number of parallel threads times some
@@ -1195,12 +1198,14 @@
 
   // A G1CollectedHeap will contain some number of heap regions.  This
   // finds the region containing a given address, or else returns NULL.
-  HeapRegion* heap_region_containing(const void* addr) const;
+  template <class T>
+  inline HeapRegion* heap_region_containing(const T addr) const;
 
   // Like the above, but requires "addr" to be in the heap (to avoid a
   // null-check), and unlike the above, may return an continuing humongous
   // region.
-  HeapRegion* heap_region_containing_raw(const void* addr) const;
+  template <class T>
+  inline HeapRegion* heap_region_containing_raw(const T addr) const;
 
   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
   // each address in the (reserved) heap is a member of exactly
@@ -1262,7 +1267,7 @@
     return true;
   }
 
-  bool is_in_young(oop obj) {
+  bool is_in_young(const oop obj) {
     HeapRegion* hr = heap_region_containing(obj);
     return hr != NULL && hr->is_young();
   }
@@ -1368,11 +1373,6 @@
   // Override
   void print_tracing_info() const;
 
-  // If "addr" is a pointer into the (reserved?) heap, returns a positive
-  // number indicating the "arena" within the heap in which "addr" falls.
-  // Or else returns 0.
-  virtual int addr_to_arena_id(void* addr) const;
-
   // Convenience function to be used in situations where the heap type can be
   // asserted to be this type.
   static G1CollectedHeap* heap();

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.inline.hpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.inline.hpp	Fri Jun 10 13:16:40 2011 -0400
@@ -34,9 +34,10 @@
 
 // Inline functions for G1CollectedHeap
 
+template <class T>
 inline HeapRegion*
-G1CollectedHeap::heap_region_containing(const void* addr) const {
-  HeapRegion* hr = _hrs->addr_to_region(addr);
+G1CollectedHeap::heap_region_containing(const T addr) const {
+  HeapRegion* hr = _hrs.addr_to_region((HeapWord*) addr);
   // hr can be null if addr in perm_gen
   if (hr != NULL && hr->continuesHumongous()) {
     hr = hr->humongous_start_region();
@@ -44,19 +45,16 @@
   return hr;
 }
 
+template <class T>
 inline HeapRegion*
-G1CollectedHeap::heap_region_containing_raw(const void* addr) const {
-  assert(_g1_reserved.contains(addr), "invariant");
-  size_t index = pointer_delta(addr, _g1_reserved.start(), 1)
-                                        >> HeapRegion::LogOfHRGrainBytes;
-
-  HeapRegion* res = _hrs->at(index);
-  assert(res == _hrs->addr_to_region(addr), "sanity");
+G1CollectedHeap::heap_region_containing_raw(const T addr) const {
+  assert(_g1_reserved.contains((const void*) addr), "invariant");
+  HeapRegion* res = _hrs.addr_to_region_unsafe((HeapWord*) addr);
   return res;
 }
 
 inline bool G1CollectedHeap::obj_in_cs(oop obj) {
-  HeapRegion* r = _hrs->addr_to_region(obj);
+  HeapRegion* r = _hrs.addr_to_region((HeapWord*) obj);
   return r != NULL && r->in_collection_set();
 }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Fri Jun 10 13:16:40 2011 -0400
@@ -2639,11 +2639,8 @@
   assert(!hr->is_young(), "non-incremental add of young region");
 
   if (G1PrintHeapRegions) {
-    gclog_or_tty->print_cr("added region to cset "
-                           "%d:["PTR_FORMAT", "PTR_FORMAT"], "
-                           "top "PTR_FORMAT", %s",
-                           hr->hrs_index(), hr->bottom(), hr->end(),
-                           hr->top(), hr->is_young() ? "YOUNG" : "NOT_YOUNG");
+    gclog_or_tty->print_cr("added region to cset "HR_FORMAT,
+                           HR_FORMAT_PARAMS(hr));
   }
 
   if (_g1->mark_in_progress())
@@ -2813,11 +2810,8 @@
   _inc_cset_tail = hr;
 
   if (G1PrintHeapRegions) {
-    gclog_or_tty->print_cr(" added region to incremental cset (RHS) "
-                  "%d:["PTR_FORMAT", "PTR_FORMAT"], "
-                  "top "PTR_FORMAT", young %s",
-                  hr->hrs_index(), hr->bottom(), hr->end(),
-                  hr->top(), (hr->is_young()) ? "YES" : "NO");
+    gclog_or_tty->print_cr(" added region to incremental cset (RHS) "HR_FORMAT,
+                           HR_FORMAT_PARAMS(hr));
   }
 }
 
@@ -2838,11 +2832,8 @@
   _inc_cset_head = hr;
 
   if (G1PrintHeapRegions) {
-    gclog_or_tty->print_cr(" added region to incremental cset (LHS) "
-                  "%d:["PTR_FORMAT", "PTR_FORMAT"], "
-                  "top "PTR_FORMAT", young %s",
-                  hr->hrs_index(), hr->bottom(), hr->end(),
-                  hr->top(), (hr->is_young()) ? "YES" : "NO");
+    gclog_or_tty->print_cr(" added region to incremental cset (LHS) "HR_FORMAT,
+                           HR_FORMAT_PARAMS(hr));
   }
 }
 

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Fri Jun 10 13:16:40 2011 -0400
@@ -159,20 +159,16 @@
               gclog_or_tty->print_cr("----------");
             }
             gclog_or_tty->print_cr("Missing rem set entry:");
-            gclog_or_tty->print_cr("Field "PTR_FORMAT
-                          " of obj "PTR_FORMAT
-                          ", in region %d ["PTR_FORMAT
-                          ", "PTR_FORMAT"),",
-                          p, (void*) _containing_obj,
-                          from->hrs_index(),
-                          from->bottom(),
-                          from->end());
+            gclog_or_tty->print_cr("Field "PTR_FORMAT" "
+                                   "of obj "PTR_FORMAT", "
+                                   "in region "HR_FORMAT,
+                                   p, (void*) _containing_obj,
+                                   HR_FORMAT_PARAMS(from));
             _containing_obj->print_on(gclog_or_tty);
-            gclog_or_tty->print_cr("points to obj "PTR_FORMAT
-                          " in region %d ["PTR_FORMAT
-                          ", "PTR_FORMAT").",
-                          (void*) obj, to->hrs_index(),
-                          to->bottom(), to->end());
+            gclog_or_tty->print_cr("points to obj "PTR_FORMAT" "
+                                   "in region "HR_FORMAT,
+                                   (void*) obj,
+                                   HR_FORMAT_PARAMS(to));
             obj->print_on(gclog_or_tty);
             gclog_or_tty->print_cr("Obj head CTE = %d, field CTE = %d.",
                           cv_obj, cv_field);
@@ -484,11 +480,10 @@
 
 
 HeapRegion::
-HeapRegion(G1BlockOffsetSharedArray* sharedOffsetArray,
-                     MemRegion mr, bool is_zeroed)
+HeapRegion(size_t hrs_index, G1BlockOffsetSharedArray* sharedOffsetArray,
+           MemRegion mr, bool is_zeroed)
   : G1OffsetTableContigSpace(sharedOffsetArray, mr, is_zeroed),
-    _next_fk(HeapRegionDCTOC::NoFilterKind),
-    _hrs_index(-1),
+    _next_fk(HeapRegionDCTOC::NoFilterKind), _hrs_index(hrs_index),
     _humongous_type(NotHumongous), _humongous_start_region(NULL),
     _in_collection_set(false), _is_gc_alloc_region(false),
     _next_in_special_set(NULL), _orig_end(NULL),

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp	Fri Jun 10 13:16:40 2011 -0400
@@ -52,9 +52,11 @@
 class HeapRegion;
 class HeapRegionSetBase;
 
-#define HR_FORMAT "%d:["PTR_FORMAT","PTR_FORMAT","PTR_FORMAT"]"
-#define HR_FORMAT_PARAMS(_hr_) (_hr_)->hrs_index(), (_hr_)->bottom(), \
-                               (_hr_)->top(), (_hr_)->end()
+#define HR_FORMAT SIZE_FORMAT":(%s)["PTR_FORMAT","PTR_FORMAT","PTR_FORMAT"]"
+#define HR_FORMAT_PARAMS(_hr_) \
+                (_hr_)->hrs_index(), \
+                (_hr_)->is_survivor() ? "S" : (_hr_)->is_young() ? "E" : "-", \
+                (_hr_)->bottom(), (_hr_)->top(), (_hr_)->end()
 
 // A dirty card to oop closure for heap regions. It
 // knows how to get the G1 heap and how to use the bitmap
@@ -237,9 +239,8 @@
   G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }
 
  protected:
-  // If this region is a member of a HeapRegionSeq, the index in that
-  // sequence, otherwise -1.
-  int  _hrs_index;
+  // The index of this region in the heap region sequence.
+  size_t  _hrs_index;
 
   HumongousType _humongous_type;
   // For a humongous region, region in which it starts.
@@ -296,8 +297,7 @@
   enum YoungType {
     NotYoung,                   // a region is not young
     Young,                      // a region is young
-    Survivor                    // a region is young and it contains
-                                // survivor
+    Survivor                    // a region is young and it contains survivors
   };
 
   volatile YoungType _young_type;
@@ -351,7 +351,8 @@
 
  public:
   // If "is_zeroed" is "true", the region "mr" can be assumed to contain zeros.
-  HeapRegion(G1BlockOffsetSharedArray* sharedOffsetArray,
+  HeapRegion(size_t hrs_index,
+             G1BlockOffsetSharedArray* sharedOffsetArray,
              MemRegion mr, bool is_zeroed);
 
   static int LogOfHRGrainBytes;
@@ -393,8 +394,7 @@
 
   // If this region is a member of a HeapRegionSeq, the index in that
   // sequence, otherwise -1.
-  int hrs_index() const { return _hrs_index; }
-  void set_hrs_index(int index) { _hrs_index = index; }
+  size_t hrs_index() const { return _hrs_index; }
 
   // The number of bytes marked live in the region in the last marking phase.
   size_t marked_bytes()    { return _prev_marked_bytes; }
@@ -579,6 +579,8 @@
   void set_next_dirty_cards_region(HeapRegion* hr) { _next_dirty_cards_region = hr; }
   bool is_on_dirty_cards_region_list() const { return get_next_dirty_cards_region() != NULL; }
 
+  HeapWord* orig_end() { return _orig_end; }
+
   // Allows logical separation between objects allocated before and after.
   void save_marks();
 

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp	Fri Jun 10 13:16:40 2011 -0400
@@ -834,7 +834,7 @@
 #endif
 
   // Set the corresponding coarse bit.
-  int max_hrs_index = max->hr()->hrs_index();
+  size_t max_hrs_index = max->hr()->hrs_index();
   if (!_coarse_map.at(max_hrs_index)) {
     _coarse_map.at_put(max_hrs_index, true);
     _n_coarse_entries++;
@@ -860,7 +860,8 @@
                               BitMap* region_bm, BitMap* card_bm) {
   // First eliminated garbage regions from the coarse map.
   if (G1RSScrubVerbose)
-    gclog_or_tty->print_cr("Scrubbing region %d:", hr()->hrs_index());
+    gclog_or_tty->print_cr("Scrubbing region "SIZE_FORMAT":",
+                           hr()->hrs_index());
 
   assert(_coarse_map.size() == region_bm->size(), "Precondition");
   if (G1RSScrubVerbose)
@@ -878,7 +879,8 @@
       PosParPRT* nxt = cur->next();
       // If the entire region is dead, eliminate.
       if (G1RSScrubVerbose)
-        gclog_or_tty->print_cr("     For other region %d:", cur->hr()->hrs_index());
+        gclog_or_tty->print_cr("     For other region "SIZE_FORMAT":",
+                               cur->hr()->hrs_index());
       if (!region_bm->at(cur->hr()->hrs_index())) {
         *prev = nxt;
         cur->set_next(NULL);
@@ -994,7 +996,7 @@
 
 void OtherRegionsTable::clear_incoming_entry(HeapRegion* from_hr) {
   MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
-  size_t hrs_ind = (size_t)from_hr->hrs_index();
+  size_t hrs_ind = from_hr->hrs_index();
   size_t ind = hrs_ind & _mod_max_fine_entries_mask;
   if (del_single_region_table(ind, from_hr)) {
     assert(!_coarse_map.at(hrs_ind), "Inv");
@@ -1002,7 +1004,7 @@
     _coarse_map.par_at_put(hrs_ind, 0);
   }
   // Check to see if any of the fcc entries come from here.
-  int hr_ind = hr()->hrs_index();
+  size_t hr_ind = hr()->hrs_index();
   for (int tid = 0; tid < HeapRegionRemSet::num_par_rem_sets(); tid++) {
     int fcc_ent = _from_card_cache[tid][hr_ind];
     if (fcc_ent != -1) {

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp	Fri Jun 10 13:16:40 2011 -0400
@@ -23,259 +23,182 @@
  */
 
 #include "precompiled.hpp"
+#include "gc_implementation/g1/heapRegion.hpp"
+#include "gc_implementation/g1/heapRegionSeq.inline.hpp"
+#include "gc_implementation/g1/heapRegionSets.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
-#include "gc_implementation/g1/heapRegionSeq.hpp"
 #include "memory/allocation.hpp"
 
-// Local to this file.
-
-static int orderRegions(HeapRegion** hr1p, HeapRegion** hr2p) {
-  if ((*hr1p)->end() <= (*hr2p)->bottom()) return -1;
-  else if ((*hr2p)->end() <= (*hr1p)->bottom()) return 1;
-  else if (*hr1p == *hr2p) return 0;
-  else {
-    assert(false, "We should never compare distinct overlapping regions.");
-  }
-  return 0;
-}
-
-HeapRegionSeq::HeapRegionSeq(const size_t max_size) :
-  _alloc_search_start(0),
-  // The line below is the worst bit of C++ hackery I've ever written
-  // (Detlefs, 11/23).  You should think of it as equivalent to
-  // "_regions(100, true)": initialize the growable array and inform it
-  // that it should allocate its elem array(s) on the C heap.
-  //
-  // The first argument, however, is actually a comma expression
-  // (set_allocation_type(this, C_HEAP), 100). The purpose of the
-  // set_allocation_type() call is to replace the default allocation
-  // type for embedded objects STACK_OR_EMBEDDED with C_HEAP. It will
-  // allow to pass the assert in GenericGrowableArray() which checks
-  // that a growable array object must be on C heap if elements are.
-  //
-  // Note: containing object is allocated on C heap since it is CHeapObj.
-  //
-  _regions((ResourceObj::set_allocation_type((address)&_regions,
-                                             ResourceObj::C_HEAP),
-            (int)max_size),
-           true),
-  _next_rr_candidate(0),
-  _seq_bottom(NULL)
-{}
-
-// Private methods.
+// Private
 
-void HeapRegionSeq::print_empty_runs() {
-  int empty_run = 0;
-  int n_empty = 0;
-  int empty_run_start;
-  for (int i = 0; i < _regions.length(); i++) {
-    HeapRegion* r = _regions.at(i);
-    if (r->continuesHumongous()) continue;
-    if (r->is_empty()) {
-      assert(!r->isHumongous(), "H regions should not be empty.");
-      if (empty_run == 0) empty_run_start = i;
-      empty_run++;
-      n_empty++;
-    } else {
-      if (empty_run > 0) {
-        gclog_or_tty->print("  %d:%d", empty_run_start, empty_run);
-        empty_run = 0;
-      }
-    }
-  }
-  if (empty_run > 0) {
-    gclog_or_tty->print(" %d:%d", empty_run_start, empty_run);
-  }
-  gclog_or_tty->print_cr(" [tot = %d]", n_empty);
-}
-
-int HeapRegionSeq::find(HeapRegion* hr) {
-  // FIXME: optimized for adjacent regions of fixed size.
-  int ind = hr->hrs_index();
-  if (ind != -1) {
-    assert(_regions.at(ind) == hr, "Mismatch");
-  }
-  return ind;
-}
-
-
-// Public methods.
+size_t HeapRegionSeq::find_contiguous_from(size_t from, size_t num) {
+  size_t len = length();
+  assert(num > 1, "use this only for sequences of length 2 or greater");
+  assert(from <= len,
+         err_msg("from: "SIZE_FORMAT" should be valid and <= than "SIZE_FORMAT,
+                 from, len));
 
-void HeapRegionSeq::insert(HeapRegion* hr) {
-  assert(!_regions.is_full(), "Too many elements in HeapRegionSeq");
-  if (_regions.length() == 0
-      || _regions.top()->end() <= hr->bottom()) {
-    hr->set_hrs_index(_regions.length());
-    _regions.append(hr);
-  } else {
-    _regions.append(hr);
-    _regions.sort(orderRegions);
-    for (int i = 0; i < _regions.length(); i++) {
-      _regions.at(i)->set_hrs_index(i);
-    }
-  }
-  char* bot = (char*)_regions.at(0)->bottom();
-  if (_seq_bottom == NULL || bot < _seq_bottom) _seq_bottom = bot;
-}
-
-size_t HeapRegionSeq::length() {
-  return _regions.length();
-}
-
-size_t HeapRegionSeq::free_suffix() {
-  size_t res = 0;
-  int first = _regions.length() - 1;
-  int cur = first;
-  while (cur >= 0 &&
-         (_regions.at(cur)->is_empty()
-          && (first == cur
-              || (_regions.at(cur+1)->bottom() ==
-                  _regions.at(cur)->end())))) {
-      res++;
-      cur--;
-  }
-  return res;
-}
-
-int HeapRegionSeq::find_contiguous_from(int from, size_t num) {
-  assert(num > 1, "pre-condition");
-  assert(0 <= from && from <= _regions.length(),
-         err_msg("from: %d should be valid and <= than %d",
-                 from, _regions.length()));
-
-  int curr = from;
-  int first = -1;
+  size_t curr = from;
+  size_t first = G1_NULL_HRS_INDEX;
   size_t num_so_far = 0;
-  while (curr < _regions.length() && num_so_far < num) {
-    HeapRegion* curr_hr = _regions.at(curr);
-    if (curr_hr->is_empty()) {
-      if (first == -1) {
+  while (curr < len && num_so_far < num) {
+    if (at(curr)->is_empty()) {
+      if (first == G1_NULL_HRS_INDEX) {
         first = curr;
         num_so_far = 1;
       } else {
         num_so_far += 1;
       }
     } else {
-      first = -1;
+      first = G1_NULL_HRS_INDEX;
       num_so_far = 0;
     }
     curr += 1;
   }
-
   assert(num_so_far <= num, "post-condition");
   if (num_so_far == num) {
     // we found enough space for the humongous object
-    assert(from <= first && first < _regions.length(), "post-condition");
-    assert(first < curr && (curr - first) == (int) num, "post-condition");
-    for (int i = first; i < first + (int) num; ++i) {
-      assert(_regions.at(i)->is_empty(), "post-condition");
+    assert(from <= first && first < len, "post-condition");
+    assert(first < curr && (curr - first) == num, "post-condition");
+    for (size_t i = first; i < first + num; ++i) {
+      assert(at(i)->is_empty(), "post-condition");
     }
     return first;
   } else {
     // we failed to find enough space for the humongous object
-    return -1;
+    return G1_NULL_HRS_INDEX;
   }
 }
 
-int HeapRegionSeq::find_contiguous(size_t num) {
-  assert(num > 1, "otherwise we should not be calling this");
-  assert(0 <= _alloc_search_start && _alloc_search_start <= _regions.length(),
-         err_msg("_alloc_search_start: %d should be valid and <= than %d",
-                 _alloc_search_start, _regions.length()));
+// Public
+
+void HeapRegionSeq::initialize(HeapWord* bottom, HeapWord* end,
+                               size_t max_length) {
+  assert((size_t) bottom % HeapRegion::GrainBytes == 0,
+         "bottom should be heap region aligned");
+  assert((size_t) end % HeapRegion::GrainBytes == 0,
+         "end should be heap region aligned");
+
+  _length = 0;
+  _heap_bottom = bottom;
+  _heap_end = end;
+  _region_shift = HeapRegion::LogOfHRGrainBytes;
+  _next_search_index = 0;
+  _allocated_length = 0;
+  _max_length = max_length;
+
+  _regions = NEW_C_HEAP_ARRAY(HeapRegion*, max_length);
+  memset(_regions, 0, max_length * sizeof(HeapRegion*));
+  _regions_biased = _regions - ((size_t) bottom >> _region_shift);
+
+  assert(&_regions[0] == &_regions_biased[addr_to_index_biased(bottom)],
+         "bottom should be included in the region with index 0");
+}
+
+MemRegion HeapRegionSeq::expand_by(HeapWord* old_end,
+                                   HeapWord* new_end,
+                                   FreeRegionList* list) {
+  assert(old_end < new_end, "don't call it otherwise");
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
+
+  HeapWord* next_bottom = old_end;
+  assert(_heap_bottom <= next_bottom, "invariant");
+  while (next_bottom < new_end) {
+    assert(next_bottom < _heap_end, "invariant");
+    size_t index = length();
 
-  int start = _alloc_search_start;
-  int res = find_contiguous_from(start, num);
-  if (res == -1 && start != 0) {
-    // Try starting from the beginning. If _alloc_search_start was 0,
-    // no point in doing this again.
-    res = find_contiguous_from(0, num);
+    assert(index < _max_length, "otherwise we cannot expand further");
+    if (index == 0) {
+      // We have not allocated any regions so far
+      assert(next_bottom == _heap_bottom, "invariant");
+    } else {
+      // next_bottom should match the end of the last/previous region
+      assert(next_bottom == at(index - 1)->end(), "invariant");
+    }
+
+    if (index == _allocated_length) {
+      // We have to allocate a new HeapRegion.
+      HeapRegion* new_hr = g1h->new_heap_region(index, next_bottom);
+      if (new_hr == NULL) {
+        // allocation failed, we bail out and return what we have done so far
+        return MemRegion(old_end, next_bottom);
+      }
+      assert(_regions[index] == NULL, "invariant");
+      _regions[index] = new_hr;
+      increment_length(&_allocated_length);
+    }
+    // Have to increment the length first, otherwise we will get an
+    // assert failure at(index) below.
+    increment_length(&_length);
+    HeapRegion* hr = at(index);
+    list->add_as_tail(hr);
+
+    next_bottom = hr->end();
   }
-  if (res != -1) {
-    assert(0 <= res && res < _regions.length(),
-           err_msg("res: %d should be valid", res));
-    _alloc_search_start = res + (int) num;
-    assert(0 < _alloc_search_start && _alloc_search_start <= _regions.length(),
-           err_msg("_alloc_search_start: %d should be valid",
-                   _alloc_search_start));
+  assert(next_bottom == new_end, "post-condition");
+  return MemRegion(old_end, next_bottom);
+}
+
+size_t HeapRegionSeq::free_suffix() {
+  size_t res = 0;
+  size_t index = length();
+  while (index > 0) {
+    index -= 1;
+    if (!at(index)->is_empty()) {
+      break;
+    }
+    res += 1;
   }
   return res;
 }
 
-void HeapRegionSeq::iterate(HeapRegionClosure* blk) {
-  iterate_from((HeapRegion*)NULL, blk);
+size_t HeapRegionSeq::find_contiguous(size_t num) {
+  assert(num > 1, "use this only for sequences of length 2 or greater");
+  assert(_next_search_index <= length(),
+         err_msg("_next_search_indeex: "SIZE_FORMAT" "
+                 "should be valid and <= than "SIZE_FORMAT,
+                 _next_search_index, length()));
+
+  size_t start = _next_search_index;
+  size_t res = find_contiguous_from(start, num);
+  if (res == G1_NULL_HRS_INDEX && start > 0) {
+    // Try starting from the beginning. If _next_search_index was 0,
+    // no point in doing this again.
+    res = find_contiguous_from(0, num);
+  }
+  if (res != G1_NULL_HRS_INDEX) {
+    assert(res < length(),
+           err_msg("res: "SIZE_FORMAT" should be valid", res));
+    _next_search_index = res + num;
+    assert(_next_search_index <= length(),
+           err_msg("_next_search_indeex: "SIZE_FORMAT" "
+                   "should be valid and <= than "SIZE_FORMAT,
+                   _next_search_index, length()));
+  }
+  return res;
 }
 
-// The first argument r is the heap region at which iteration begins.
-// This operation runs fastest when r is NULL, or the heap region for
-// which a HeapRegionClosure most recently returned true, or the
-// heap region immediately to its right in the sequence.  In all
-// other cases a linear search is required to find the index of r.
-
-void HeapRegionSeq::iterate_from(HeapRegion* r, HeapRegionClosure* blk) {
-
-  // :::: FIXME ::::
-  // Static cache value is bad, especially when we start doing parallel
-  // remembered set update. For now just don't cache anything (the
-  // code in the def'd out blocks).
+void HeapRegionSeq::iterate(HeapRegionClosure* blk) const {
+  iterate_from((HeapRegion*) NULL, blk);
+}
 
-#if 0
-  static int cached_j = 0;
-#endif
-  int len = _regions.length();
-  int j = 0;
-  // Find the index of r.
-  if (r != NULL) {
-#if 0
-    assert(cached_j >= 0, "Invariant.");
-    if ((cached_j < len) && (r == _regions.at(cached_j))) {
-      j = cached_j;
-    } else if ((cached_j + 1 < len) && (r == _regions.at(cached_j + 1))) {
-      j = cached_j + 1;
-    } else {
-      j = find(r);
-#endif
-      if (j < 0) {
-        j = 0;
-      }
-#if 0
-    }
-#endif
+void HeapRegionSeq::iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const {
+  size_t hr_index = 0;
+  if (hr != NULL) {
+    hr_index = (size_t) hr->hrs_index();
   }
-  int i;
-  for (i = j; i < len; i += 1) {
-    int res = blk->doHeapRegion(_regions.at(i));
+
+  size_t len = length();
+  for (size_t i = hr_index; i < len; i += 1) {
+    bool res = blk->doHeapRegion(at(i));
     if (res) {
-#if 0
-      cached_j = i;
-#endif
       blk->incomplete();
       return;
     }
   }
-  for (i = 0; i < j; i += 1) {
-    int res = blk->doHeapRegion(_regions.at(i));
+  for (size_t i = 0; i < hr_index; i += 1) {
+    bool res = blk->doHeapRegion(at(i));
     if (res) {
-#if 0
-      cached_j = i;
-#endif
-      blk->incomplete();
-      return;
-    }
-  }
-}
-
-void HeapRegionSeq::iterate_from(int idx, HeapRegionClosure* blk) {
-  int len = _regions.length();
-  int i;
-  for (i = idx; i < len; i++) {
-    if (blk->doHeapRegion(_regions.at(i))) {
-      blk->incomplete();
-      return;
-    }
-  }
-  for (i = 0; i < idx; i++) {
-    if (blk->doHeapRegion(_regions.at(i))) {
       blk->incomplete();
       return;
     }
@@ -283,54 +206,92 @@
 }
 
 MemRegion HeapRegionSeq::shrink_by(size_t shrink_bytes,
-                                   size_t& num_regions_deleted) {
+                                   size_t* num_regions_deleted) {
   // Reset this in case it's currently pointing into the regions that
   // we just removed.
-  _alloc_search_start = 0;
+  _next_search_index = 0;
 
   assert(shrink_bytes % os::vm_page_size() == 0, "unaligned");
   assert(shrink_bytes % HeapRegion::GrainBytes == 0, "unaligned");
+  assert(length() > 0, "the region sequence should not be empty");
+  assert(length() <= _allocated_length, "invariant");
+  assert(_allocated_length > 0, "we should have at least one region committed");
 
-  if (_regions.length() == 0) {
-    num_regions_deleted = 0;
-    return MemRegion();
-  }
-  int j = _regions.length() - 1;
-  HeapWord* end = _regions.at(j)->end();
+  // around the loop, i will be the next region to be removed
+  size_t i = length() - 1;
+  assert(i > 0, "we should never remove all regions");
+  // [last_start, end) is the MemRegion that covers the regions we will remove.
+  HeapWord* end = at(i)->end();
   HeapWord* last_start = end;
-  while (j >= 0 && shrink_bytes > 0) {
-    HeapRegion* cur = _regions.at(j);
-    // We have to leave humongous regions where they are,
-    // and work around them.
-    if (cur->isHumongous()) {
-      return MemRegion(last_start, end);
-    }
-    assert(cur == _regions.top(), "Should be top");
+  *num_regions_deleted = 0;
+  while (shrink_bytes > 0) {
+    HeapRegion* cur = at(i);
+    // We should leave the humongous regions where they are.
+    if (cur->isHumongous()) break;
+    // We should stop shrinking if we come across a non-empty region.
     if (!cur->is_empty()) break;
+
+    i -= 1;
+    *num_regions_deleted += 1;
     shrink_bytes -= cur->capacity();
-    num_regions_deleted++;
-    _regions.pop();
     last_start = cur->bottom();
-    // We need to delete these somehow, but can't currently do so here: if
-    // we do, the ZF thread may still access the deleted region.  We'll
-    // leave this here as a reminder that we have to do something about
-    // this.
-    // delete cur;
-    j--;
+    decrement_length(&_length);
+    // We will reclaim the HeapRegion. _allocated_length should be
+    // covering this index. So, even though we removed the region from
+    // the active set by decreasing _length, we still have it
+    // available in the future if we need to re-use it.
+    assert(i > 0, "we should never remove all regions");
+    assert(length() > 0, "we should never remove all regions");
   }
   return MemRegion(last_start, end);
 }
 
-class PrintHeapRegionClosure : public  HeapRegionClosure {
-public:
-  bool doHeapRegion(HeapRegion* r) {
-    gclog_or_tty->print(PTR_FORMAT ":", r);
-    r->print();
-    return false;
+#ifndef PRODUCT
+void HeapRegionSeq::verify_optional() {
+  guarantee(_length <= _allocated_length,
+            err_msg("invariant: _length: "SIZE_FORMAT" "
+                    "_allocated_length: "SIZE_FORMAT,
+                    _length, _allocated_length));
+  guarantee(_allocated_length <= _max_length,
+            err_msg("invariant: _allocated_length: "SIZE_FORMAT" "
+                    "_max_length: "SIZE_FORMAT,
+                    _allocated_length, _max_length));
+  guarantee(_next_search_index <= _length,
+            err_msg("invariant: _next_search_index: "SIZE_FORMAT" "
+                    "_length: "SIZE_FORMAT,
+                    _next_search_index, _length));
+
+  HeapWord* prev_end = _heap_bottom;
+  for (size_t i = 0; i < _allocated_length; i += 1) {
+    HeapRegion* hr = _regions[i];
+    guarantee(hr != NULL, err_msg("invariant: i: "SIZE_FORMAT, i));
+    guarantee(hr->bottom() == prev_end,
+              err_msg("invariant i: "SIZE_FORMAT" "HR_FORMAT" "
+                      "prev_end: "PTR_FORMAT,
+                      i, HR_FORMAT_PARAMS(hr), prev_end));
+    guarantee(hr->hrs_index() == i,
+              err_msg("invariant: i: "SIZE_FORMAT" hrs_index(): "SIZE_FORMAT,
+                      i, hr->hrs_index()));
+    if (i < _length) {
+      // Asserts will fire if i is >= _length
+      HeapWord* addr = hr->bottom();
+      guarantee(addr_to_region(addr) == hr, "sanity");
+      guarantee(addr_to_region_unsafe(addr) == hr, "sanity");
+    } else {
+      guarantee(hr->is_empty(), "sanity");
+      guarantee(!hr->isHumongous(), "sanity");
+      // using assert instead of guarantee here since containing_set()
+      // is only available in non-product builds.
+      assert(hr->containing_set() == NULL, "sanity");
+    }
+    if (hr->startsHumongous()) {
+      prev_end = hr->orig_end();
+    } else {
+      prev_end = hr->end();
+    }
   }
-};
-
-void HeapRegionSeq::print() {
-  PrintHeapRegionClosure cl;
-  iterate(&cl);
+  for (size_t i = _allocated_length; i < _max_length; i += 1) {
+    guarantee(_regions[i] == NULL, err_msg("invariant i: "SIZE_FORMAT, i));
+  }
 }
+#endif // PRODUCT

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.hpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.hpp	Fri Jun 10 13:16:40 2011 -0400
@@ -25,92 +25,143 @@
 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
 
-#include "gc_implementation/g1/heapRegion.hpp"
-#include "utilities/growableArray.hpp"
-
 class HeapRegion;
 class HeapRegionClosure;
+class FreeRegionList;
+
+#define G1_NULL_HRS_INDEX ((size_t) -1)
+
+// This class keeps track of the region metadata (i.e., HeapRegion
+// instances). They are kept in the _regions array in address
+// order. A region's index in the array corresponds to its index in
+// the heap (i.e., 0 is the region at the bottom of the heap, 1 is
+// the one after it, etc.). Two regions that are consecutive in the
+// array should also be adjacent in the address space (i.e.,
+// region(i).end() == region(i+1).bottom().
+//
+// We create a HeapRegion when we commit the region's address space
+// for the first time. When we uncommit the address space of a
+// region we retain the HeapRegion to be able to re-use it in the
+// future (in case we recommit it).
+//
+// We keep track of three lengths:
+//
+// * _length (returned by length()) is the number of currently
+//   committed regions.
+// * _allocated_length (not exposed outside this class) is the
+//   number of regions for which we have HeapRegions.
+// * _max_length (returned by max_length()) is the maximum number of
+//   regions the heap can have.
+//
+// and maintain that: _length <= _allocated_length <= _max_length
 
 class HeapRegionSeq: public CHeapObj {
 
-  // _regions is kept sorted by start address order, and no two regions are
-  // overlapping.
-  GrowableArray<HeapRegion*> _regions;
+  // The array that holds the HeapRegions.
+  HeapRegion** _regions;
+
+  // Version of _regions biased to address 0
+  HeapRegion** _regions_biased;
+
+  // The number of regions committed in the heap.
+  size_t _length;
 
-  // The index in "_regions" at which to start the next allocation search.
-  // (For efficiency only; private to obj_allocate after initialization.)
-  int _alloc_search_start;
+  // The address of the first reserved word in the heap.
+  HeapWord* _heap_bottom;
+
+  // The address of the last reserved word in the heap - 1.
+  HeapWord* _heap_end;
+
+  // The log of the region byte size.
+  size_t _region_shift;
+
+  // A hint for which index to start searching from for humongous
+  // allocations.
+  size_t _next_search_index;
 
-  // Finds a contiguous set of empty regions of length num, starting
-  // from a given index.
-  int find_contiguous_from(int from, size_t num);
+  // The number of regions for which we have allocated HeapRegions for.
+  size_t _allocated_length;
+
+  // The maximum number of regions in the heap.
+  size_t _max_length;
+
+  // Find a contiguous set of empty regions of length num, starting
+  // from the given index.
+  size_t find_contiguous_from(size_t from, size_t num);
 
-  // Currently, we're choosing collection sets in a round-robin fashion,
-  // starting here.
-  int _next_rr_candidate;
+  // Map a heap address to a biased region index. Assume that the
+  // address is valid.
+  inline size_t addr_to_index_biased(HeapWord* addr) const;
 
-  // The bottom address of the bottom-most region, or else NULL if there
-  // are no regions in the sequence.
-  char* _seq_bottom;
+  void increment_length(size_t* length) {
+    assert(*length < _max_length, "pre-condition");
+    *length += 1;
+  }
+
+  void decrement_length(size_t* length) {
+    assert(*length > 0, "pre-condition");
+    *length -= 1;
+  }
 
  public:
-  // Initializes "this" to the empty sequence of regions.
-  HeapRegionSeq(const size_t max_size);
+  // Empty contructor, we'll initialize it with the initialize() method.
+  HeapRegionSeq() { }
+
+  void initialize(HeapWord* bottom, HeapWord* end, size_t max_length);
 
-  // Adds "hr" to "this" sequence.  Requires "hr" not to overlap with
-  // any region already in "this".  (Will perform better if regions are
-  // inserted in ascending address order.)
-  void insert(HeapRegion* hr);
+  // Return the HeapRegion at the given index. Assume that the index
+  // is valid.
+  inline HeapRegion* at(size_t index) const;
+
+  // If addr is within the committed space return its corresponding
+  // HeapRegion, otherwise return NULL.
+  inline HeapRegion* addr_to_region(HeapWord* addr) const;
+
+  // Return the HeapRegion that corresponds to the given
+  // address. Assume the address is valid.
+  inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const;
 
-  // Given a HeapRegion*, returns its index within _regions,
-  // or returns -1 if not found.
-  int find(HeapRegion* hr);
+  // Return the number of regions that have been committed in the heap.
+  size_t length() const { return _length; }
+
+  // Return the maximum number of regions in the heap.
+  size_t max_length() const { return _max_length; }
 
-  // Requires the index to be valid, and return the region at the index.
-  HeapRegion* at(size_t i) { return _regions.at((int)i); }
+  // Expand the sequence to reflect that the heap has grown from
+  // old_end to new_end. Either create new HeapRegions, or re-use
+  // existing ones, and return them in the given list. Returns the
+  // memory region that covers the newly-created regions. If a
+  // HeapRegion allocation fails, the result memory region might be
+  // smaller than the desired one.
+  MemRegion expand_by(HeapWord* old_end, HeapWord* new_end,
+                      FreeRegionList* list);
 
-  // Return the number of regions in the sequence.
-  size_t length();
-
-  // Returns the number of contiguous regions at the end of the sequence
+  // Return the number of contiguous regions at the end of the sequence
   // that are available for allocation.
   size_t free_suffix();
 
   // Find a contiguous set of empty regions of length num and return
-  // the index of the first region or -1 if the search was unsuccessful.
-  int find_contiguous(size_t num);
+  // the index of the first region or G1_NULL_HRS_INDEX if the
+  // search was unsuccessful.
+  size_t find_contiguous(size_t num);
 
-  // Apply the "doHeapRegion" method of "blk" to all regions in "this",
-  // in address order, terminating the iteration early
-  // if the "doHeapRegion" method returns "true".
-  void iterate(HeapRegionClosure* blk);
-
-  // Apply the "doHeapRegion" method of "blk" to all regions in "this",
-  // starting at "r" (or first region, if "r" is NULL), in a circular
-  // manner, terminating the iteration early if the "doHeapRegion" method
-  // returns "true".
-  void iterate_from(HeapRegion* r, HeapRegionClosure* blk);
+  // Apply blk->doHeapRegion() on all committed regions in address order,
+  // terminating the iteration early if doHeapRegion() returns true.
+  void iterate(HeapRegionClosure* blk) const;
 
-  // As above, but start from a given index in the sequence
-  // instead of a given heap region.
-  void iterate_from(int idx, HeapRegionClosure* blk);
+  // As above, but start the iteration from hr and loop around. If hr
+  // is NULL, we start from the first region in the heap.
+  void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
 
-  // Requires "shrink_bytes" to be a multiple of the page size and heap
-  // region granularity.  Deletes as many "rightmost" completely free heap
-  // regions from the sequence as comprise shrink_bytes bytes.  Returns the
-  // MemRegion indicating the region those regions comprised, and sets
-  // "num_regions_deleted" to the number of regions deleted.
-  MemRegion shrink_by(size_t shrink_bytes, size_t& num_regions_deleted);
+  // Tag as uncommitted as many regions that are completely free as
+  // possible, up to shrink_bytes, from the suffix of the committed
+  // sequence. Return a MemRegion that corresponds to the address
+  // range of the uncommitted regions. Assume shrink_bytes is page and
+  // heap region aligned.
+  MemRegion shrink_by(size_t shrink_bytes, size_t* num_regions_deleted);
 
-  // If "addr" falls within a region in the sequence, return that region,
-  // or else NULL.
-  inline HeapRegion* addr_to_region(const void* addr);
-
-  void print();
-
-  // Prints out runs of empty regions.
-  void print_empty_runs();
-
+  // Do some sanity checking.
+  void verify_optional() PRODUCT_RETURN;
 };
 
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.inline.hpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionSeq.inline.hpp	Fri Jun 10 13:16:40 2011 -0400
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2011, 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
@@ -25,23 +25,42 @@
 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_INLINE_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_INLINE_HPP
 
+#include "gc_implementation/g1/heapRegion.hpp"
 #include "gc_implementation/g1/heapRegionSeq.hpp"
 
-inline HeapRegion* HeapRegionSeq::addr_to_region(const void* addr) {
-  assert(_seq_bottom != NULL, "bad _seq_bottom in addr_to_region");
-  if ((char*) addr >= _seq_bottom) {
-    size_t diff = (size_t) pointer_delta((HeapWord*) addr,
-                                         (HeapWord*) _seq_bottom);
-    int index = (int) (diff >> HeapRegion::LogOfHRGrainWords);
-    assert(index >= 0, "invariant / paranoia");
-    if (index < _regions.length()) {
-      HeapRegion* hr = _regions.at(index);
-      assert(hr->is_in_reserved(addr),
-             "addr_to_region is wrong...");
-      return hr;
-    }
+inline size_t HeapRegionSeq::addr_to_index_biased(HeapWord* addr) const {
+  assert(_heap_bottom <= addr && addr < _heap_end,
+         err_msg("addr: "PTR_FORMAT" bottom: "PTR_FORMAT" end: "PTR_FORMAT,
+                 addr, _heap_bottom, _heap_end));
+  size_t index = (size_t) addr >> _region_shift;
+  return index;
+}
+
+inline HeapRegion* HeapRegionSeq::addr_to_region_unsafe(HeapWord* addr) const {
+  assert(_heap_bottom <= addr && addr < _heap_end,
+         err_msg("addr: "PTR_FORMAT" bottom: "PTR_FORMAT" end: "PTR_FORMAT,
+                 addr, _heap_bottom, _heap_end));
+  size_t index_biased = addr_to_index_biased(addr);
+  HeapRegion* hr = _regions_biased[index_biased];
+  assert(hr != NULL, "invariant");
+  return hr;
+}
+
+inline HeapRegion* HeapRegionSeq::addr_to_region(HeapWord* addr) const {
+  if (addr != NULL && addr < _heap_end) {
+    assert(addr >= _heap_bottom,
+          err_msg("addr: "PTR_FORMAT" bottom: "PTR_FORMAT, addr, _heap_bottom));
+    return addr_to_region_unsafe(addr);
   }
   return NULL;
 }
 
+inline HeapRegion* HeapRegionSeq::at(size_t index) const {
+  assert(index < length(), "pre-condition");
+  HeapRegion* hr = _regions[index];
+  assert(hr != NULL, "sanity");
+  assert(hr->hrs_index() == index, "sanity");
+  return hr;
+}
+
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_INLINE_HPP

--- a/hotspot/src/share/vm/gc_implementation/g1/sparsePRT.cpp	Wed Jun 08 21:48:38 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/sparsePRT.cpp	Fri Jun 10 13:16:40 2011 -0400
@@ -481,8 +481,9 @@
 
 bool SparsePRT::add_card(RegionIdx_t region_id, CardIdx_t card_index) {
 #if SPARSE_PRT_VERBOSE
-  gclog_or_tty->print_cr("  Adding card %d from region %d to region %d sparse.",
-                card_index, region_id, _hr->hrs_index());
+  gclog_or_tty->print_cr("  Adding card %d from region %d to region "
+                         SIZE_FORMAT" sparse.",
+                         card_index, region_id, _hr->hrs_index());
 #endif
   if (_next->occupied_entries() * 2 > _next->capacity()) {
     expand();
@@ -533,8 +534,8 @@
   _next = new RSHashTable(last->capacity() * 2);
 
 #if SPARSE_PRT_VERBOSE
-  gclog_or_tty->print_cr("  Expanded sparse table for %d to %d.",
-                _hr->hrs_index(), _next->capacity());
+  gclog_or_tty->print_cr("  Expanded sparse table for "SIZE_FORMAT" to %d.",
+                         _hr->hrs_index(), _next->capacity());
 #endif
   for (size_t i = 0; i < last->capacity(); i++) {
     SparsePRTEntry* e = last->entry((int)i);