changeset 4644:73652d89e7c4

Merge
author stefank
date Fri, 10 May 2013 09:24:20 +0200
parents d3c98423c146 194f52aa2f23
children 69494caf5790
files
diffstat 27 files changed, 1166 insertions(+), 953 deletions(-) [+]
line wrap: on
line diff
--- a/make/excludeSrc.make	Thu May 09 16:27:51 2013 -0400
+++ b/make/excludeSrc.make	Fri May 10 09:24:20 2013 +0200
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2013, 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
@@ -81,22 +81,25 @@
 	cmsAdaptiveSizePolicy.cpp cmsCollectorPolicy.cpp \
 	cmsGCAdaptivePolicyCounters.cpp cmsLockVerifier.cpp compactibleFreeListSpace.cpp \
 	concurrentMarkSweepGeneration.cpp concurrentMarkSweepThread.cpp \
-	freeChunk.cpp adaptiveFreeList.cpp promotionInfo.cpp vmCMSOperations.cpp collectionSetChooser.cpp \
-	concurrentG1Refine.cpp concurrentG1RefineThread.cpp concurrentMark.cpp concurrentMarkThread.cpp \
-	dirtyCardQueue.cpp g1AllocRegion.cpp g1BlockOffsetTable.cpp g1CollectedHeap.cpp g1GCPhaseTimes.cpp \
-	g1CollectorPolicy.cpp g1ErgoVerbose.cpp g1_globals.cpp g1HRPrinter.cpp g1MarkSweep.cpp \
-	g1MMUTracker.cpp g1MonitoringSupport.cpp g1RemSet.cpp g1SATBCardTableModRefBS.cpp heapRegion.cpp \
-	heapRegionRemSet.cpp heapRegionSeq.cpp heapRegionSet.cpp heapRegionSets.cpp ptrQueue.cpp \
-	satbQueue.cpp sparsePRT.cpp survRateGroup.cpp vm_operations_g1.cpp adjoiningGenerations.cpp \
-	adjoiningVirtualSpaces.cpp asPSOldGen.cpp asPSYoungGen.cpp cardTableExtension.cpp \
-	gcTaskManager.cpp gcTaskThread.cpp objectStartArray.cpp parallelScavengeHeap.cpp parMarkBitMap.cpp \
-	pcTasks.cpp psAdaptiveSizePolicy.cpp psCompactionManager.cpp psGCAdaptivePolicyCounters.cpp \
-	psGenerationCounters.cpp psMarkSweep.cpp psMarkSweepDecorator.cpp psOldGen.cpp psParallelCompact.cpp \
-	psPromotionLAB.cpp psPromotionManager.cpp psScavenge.cpp psTasks.cpp psVirtualspace.cpp \
-	psYoungGen.cpp vmPSOperations.cpp asParNewGeneration.cpp parCardTableModRefBS.cpp \
-	parGCAllocBuffer.cpp parNewGeneration.cpp mutableSpace.cpp gSpaceCounters.cpp allocationStats.cpp \
-	spaceCounters.cpp gcAdaptivePolicyCounters.cpp mutableNUMASpace.cpp immutableSpace.cpp \
-	immutableSpace.cpp g1MemoryPool.cpp psMemoryPool.cpp yieldingWorkGroup.cpp g1Log.cpp
+	freeChunk.cpp adaptiveFreeList.cpp promotionInfo.cpp vmCMSOperations.cpp \
+	collectionSetChooser.cpp concurrentG1Refine.cpp concurrentG1RefineThread.cpp \
+	concurrentMark.cpp concurrentMarkThread.cpp dirtyCardQueue.cpp g1AllocRegion.cpp \
+	g1BlockOffsetTable.cpp g1CardCounts.cpp g1CollectedHeap.cpp g1CollectorPolicy.cpp \
+	g1ErgoVerbose.cpp g1GCPhaseTimes.cpp g1HRPrinter.cpp g1HotCardCache.cpp g1Log.cpp \
+	g1MMUTracker.cpp g1MarkSweep.cpp g1MemoryPool.cpp g1MonitoringSupport.cpp \
+	g1RemSet.cpp g1SATBCardTableModRefBS.cpp g1_globals.cpp heapRegion.cpp \
+	heapRegionRemSet.cpp heapRegionSeq.cpp heapRegionSet.cpp heapRegionSets.cpp \
+	ptrQueue.cpp satbQueue.cpp sparsePRT.cpp survRateGroup.cpp vm_operations_g1.cpp \
+	adjoiningGenerations.cpp adjoiningVirtualSpaces.cpp asPSOldGen.cpp asPSYoungGen.cpp \
+	cardTableExtension.cpp gcTaskManager.cpp gcTaskThread.cpp objectStartArray.cpp \
+	parallelScavengeHeap.cpp parMarkBitMap.cpp pcTasks.cpp psAdaptiveSizePolicy.cpp \
+	psCompactionManager.cpp psGCAdaptivePolicyCounters.cpp psGenerationCounters.cpp \
+	psMarkSweep.cpp psMarkSweepDecorator.cpp psMemoryPool.cpp psOldGen.cpp \
+	psParallelCompact.cpp psPromotionLAB.cpp psPromotionManager.cpp psScavenge.cpp \
+	psTasks.cpp psVirtualspace.cpp psYoungGen.cpp vmPSOperations.cpp asParNewGeneration.cpp \
+	parCardTableModRefBS.cpp parGCAllocBuffer.cpp parNewGeneration.cpp mutableSpace.cpp \
+	gSpaceCounters.cpp allocationStats.cpp spaceCounters.cpp gcAdaptivePolicyCounters.cpp \
+	mutableNUMASpace.cpp immutableSpace.cpp yieldingWorkGroup.cpp
 endif 
 
 ifeq ($(INCLUDE_NMT), false)
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp	Fri May 10 09:24:20 2013 +0200
@@ -193,7 +193,8 @@
      FreeBlockDictionary<FreeChunk>::DictionaryChoice dictionaryChoice) :
   CardGeneration(rs, initial_byte_size, level, ct),
   _dilatation_factor(((double)MinChunkSize)/((double)(CollectedHeap::min_fill_size()))),
-  _debug_collection_type(Concurrent_collection_type)
+  _debug_collection_type(Concurrent_collection_type),
+  _did_compact(false)
 {
   HeapWord* bottom = (HeapWord*) _virtual_space.low();
   HeapWord* end    = (HeapWord*) _virtual_space.high();
@@ -917,18 +918,15 @@
     return;
   }
 
-  // Compute some numbers about the state of the heap.
-  const size_t used_after_gc = used();
-  const size_t capacity_after_gc = capacity();
+  // The heap has been compacted but not reset yet.
+  // Any metric such as free() or used() will be incorrect.
 
   CardGeneration::compute_new_size();
 
   // Reset again after a possible resizing
-  cmsSpace()->reset_after_compaction();
-
-  assert(used() == used_after_gc && used_after_gc <= capacity(),
-         err_msg("used: " SIZE_FORMAT " used_after_gc: " SIZE_FORMAT
-         " capacity: " SIZE_FORMAT, used(), used_after_gc, capacity()));
+  if (did_compact()) {
+    cmsSpace()->reset_after_compaction();
+  }
 }
 
 void ConcurrentMarkSweepGeneration::compute_new_size_free_list() {
@@ -1578,6 +1576,8 @@
   return false;
 }
 
+void CMSCollector::set_did_compact(bool v) { _cmsGen->set_did_compact(v); }
+
 // Clear _expansion_cause fields of constituent generations
 void CMSCollector::clear_expansion_cause() {
   _cmsGen->clear_expansion_cause();
@@ -1675,7 +1675,6 @@
   }
   acquire_control_and_collect(full, clear_all_soft_refs);
   _full_gcs_since_conc_gc++;
-
 }
 
 void CMSCollector::request_full_gc(unsigned int full_gc_count) {
@@ -1857,6 +1856,7 @@
     }
   }
 
+  set_did_compact(should_compact);
   if (should_compact) {
     // If the collection is being acquired from the background
     // collector, there may be references on the discovered
@@ -2718,6 +2718,7 @@
     Chunk::clean_chunk_pool();
   }
 
+  set_did_compact(false);
   _between_prologue_and_epilogue = false;  // ready for next cycle
 }
 
--- a/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp	Fri May 10 09:24:20 2013 +0200
@@ -604,6 +604,8 @@
   ConcurrentMarkSweepPolicy* _collector_policy;
   ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
 
+  void set_did_compact(bool v);
+
   // XXX Move these to CMSStats ??? FIX ME !!!
   elapsedTimer _inter_sweep_timer;   // time between sweeps
   elapsedTimer _intra_sweep_timer;   // time _in_ sweeps
@@ -1081,6 +1083,10 @@
 
   CollectionTypes _debug_collection_type;
 
+  // True if a compactiing collection was done.
+  bool _did_compact;
+  bool did_compact() { return _did_compact; }
+
   // Fraction of current occupancy at which to start a CMS collection which
   // will collect this generation (at least).
   double _initiating_occupancy;
@@ -1121,6 +1127,8 @@
   // Adaptive size policy
   CMSAdaptiveSizePolicy* size_policy();
 
+  void set_did_compact(bool v) { _did_compact = v; }
+
   bool refs_discovery_is_atomic() const { return false; }
   bool refs_discovery_is_mt()     const {
     // Note: CMS does MT-discovery during the parallel-remark
--- a/src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp	Fri May 10 09:24:20 2013 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2013, 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
@@ -26,40 +26,12 @@
 #include "gc_implementation/g1/concurrentG1Refine.hpp"
 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
-#include "gc_implementation/g1/g1CollectorPolicy.hpp"
-#include "gc_implementation/g1/g1GCPhaseTimes.hpp"
-#include "gc_implementation/g1/g1RemSet.hpp"
-#include "gc_implementation/g1/heapRegionSeq.inline.hpp"
-#include "memory/space.inline.hpp"
-#include "runtime/atomic.hpp"
-#include "runtime/java.hpp"
-#include "utilities/copy.hpp"
+#include "gc_implementation/g1/g1HotCardCache.hpp"
 
-// Possible sizes for the card counts cache: odd primes that roughly double in size.
-// (See jvmtiTagMap.cpp).
-
-#define MAX_SIZE ((size_t) -1)
-
-size_t ConcurrentG1Refine::_cc_cache_sizes[] = {
-          16381,    32771,    76831,    150001,   307261,
-         614563,  1228891,  2457733,   4915219,  9830479,
-       19660831, 39321619, 78643219, 157286461,  MAX_SIZE
-  };
-
-ConcurrentG1Refine::ConcurrentG1Refine() :
-  _card_counts(NULL), _card_epochs(NULL),
-  _n_card_counts(0), _max_cards(0), _max_n_card_counts(0),
-  _cache_size_index(0), _expand_card_counts(false),
-  _hot_cache(NULL),
-  _def_use_cache(false), _use_cache(false),
-  // We initialize the epochs of the array to 0. By initializing
-  // _n_periods to 1 and not 0 we automatically invalidate all the
-  // entries on the array. Otherwise we might accidentally think that
-  // we claimed a card that was in fact never set (see CR7033292).
-  _n_periods(1),
-  _threads(NULL), _n_threads(0)
+ConcurrentG1Refine::ConcurrentG1Refine(G1CollectedHeap* g1h) :
+  _threads(NULL), _n_threads(0),
+  _hot_card_cache(g1h)
 {
-
   // Ergomonically select initial concurrent refinement parameters
   if (FLAG_IS_DEFAULT(G1ConcRefinementGreenZone)) {
     FLAG_SET_DEFAULT(G1ConcRefinementGreenZone, MAX2<int>(ParallelGCThreads, 1));
@@ -75,13 +47,17 @@
     FLAG_SET_DEFAULT(G1ConcRefinementRedZone, yellow_zone() * 2);
   }
   set_red_zone(MAX2<int>(G1ConcRefinementRedZone, yellow_zone()));
+
   _n_worker_threads = thread_num();
   // We need one extra thread to do the young gen rset size sampling.
   _n_threads = _n_worker_threads + 1;
+
   reset_threshold_step();
 
   _threads = NEW_C_HEAP_ARRAY(ConcurrentG1RefineThread*, _n_threads, mtGC);
+
   int worker_id_offset = (int)DirtyCardQueueSet::num_par_ids();
+
   ConcurrentG1RefineThread *next = NULL;
   for (int i = _n_threads - 1; i >= 0; i--) {
     ConcurrentG1RefineThread* t = new ConcurrentG1RefineThread(this, next, worker_id_offset, i);
@@ -100,74 +76,8 @@
   }
 }
 
-int ConcurrentG1Refine::thread_num() {
-  return MAX2<int>((G1ConcRefinementThreads > 0) ? G1ConcRefinementThreads : ParallelGCThreads, 1);
-}
-
 void ConcurrentG1Refine::init() {
-  if (G1ConcRSLogCacheSize > 0) {
-    _g1h = G1CollectedHeap::heap();
-
-    _max_cards = _g1h->max_capacity() >> CardTableModRefBS::card_shift;
-    _max_n_card_counts = _max_cards * G1MaxHotCardCountSizePercent / 100;
-
-    size_t max_card_num = ((size_t)1 << (sizeof(unsigned)*BitsPerByte-1)) - 1;
-    guarantee(_max_cards < max_card_num, "card_num representation");
-
-    // We need _n_card_counts to be less than _max_n_card_counts here
-    // so that the expansion call (below) actually allocates the
-    // _counts and _epochs arrays.
-    assert(_n_card_counts == 0, "pre-condition");
-    assert(_max_n_card_counts > 0, "pre-condition");
-
-    // Find the index into cache size array that is of a size that's
-    // large enough to hold desired_sz.
-    size_t desired_sz = _max_cards / InitialCacheFraction;
-    int desired_sz_index = 0;
-    while (_cc_cache_sizes[desired_sz_index] < desired_sz) {
-      desired_sz_index += 1;
-      assert(desired_sz_index <  MAX_CC_CACHE_INDEX, "invariant");
-    }
-    assert(desired_sz_index <  MAX_CC_CACHE_INDEX, "invariant");
-
-    // If the desired_sz value is between two sizes then
-    // _cc_cache_sizes[desired_sz_index-1] < desired_sz <= _cc_cache_sizes[desired_sz_index]
-    // we will start with the lower size in the optimistic expectation that
-    // we will not need to expand up. Note desired_sz_index could also be 0.
-    if (desired_sz_index > 0 &&
-        _cc_cache_sizes[desired_sz_index] > desired_sz) {
-      desired_sz_index -= 1;
-    }
-
-    if (!expand_card_count_cache(desired_sz_index)) {
-      // Allocation was unsuccessful - exit
-      vm_exit_during_initialization("Could not reserve enough space for card count cache");
-    }
-    assert(_n_card_counts > 0, "post-condition");
-    assert(_cache_size_index == desired_sz_index, "post-condition");
-
-    Copy::fill_to_bytes(&_card_counts[0],
-                        _n_card_counts * sizeof(CardCountCacheEntry));
-    Copy::fill_to_bytes(&_card_epochs[0], _n_card_counts * sizeof(CardEpochCacheEntry));
-
-    ModRefBarrierSet* bs = _g1h->mr_bs();
-    guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
-    _ct_bs = (CardTableModRefBS*)bs;
-    _ct_bot = _ct_bs->byte_for_const(_g1h->reserved_region().start());
-
-    _def_use_cache = true;
-    _use_cache = true;
-    _hot_cache_size = (1 << G1ConcRSLogCacheSize);
-    _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size, mtGC);
-    _n_hot = 0;
-    _hot_cache_idx = 0;
-
-    // For refining the cards in the hot cache in parallel
-    int n_workers = (ParallelGCThreads > 0 ?
-                        _g1h->workers()->total_workers() : 1);
-    _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / n_workers);
-    _hot_cache_par_claimed_idx = 0;
-  }
+  _hot_card_cache.initialize();
 }
 
 void ConcurrentG1Refine::stop() {
@@ -188,17 +98,6 @@
 }
 
 ConcurrentG1Refine::~ConcurrentG1Refine() {
-  if (G1ConcRSLogCacheSize > 0) {
-    // Please see the comment in allocate_card_count_cache
-    // for why we call os::malloc() and os::free() directly.
-    assert(_card_counts != NULL, "Logic");
-    os::free(_card_counts, mtGC);
-    assert(_card_epochs != NULL, "Logic");
-    os::free(_card_epochs, mtGC);
-
-    assert(_hot_cache != NULL, "Logic");
-    FREE_C_HEAP_ARRAY(jbyte*, _hot_cache, mtGC);
-  }
   if (_threads != NULL) {
     for (int i = 0; i < _n_threads; i++) {
       delete _threads[i];
@@ -215,317 +114,10 @@
   }
 }
 
-bool ConcurrentG1Refine::is_young_card(jbyte* card_ptr) {
-  HeapWord* start = _ct_bs->addr_for(card_ptr);
-  HeapRegion* r = _g1h->heap_region_containing(start);
-  if (r != NULL && r->is_young()) {
-    return true;
-  }
-  // This card is not associated with a heap region
-  // so can't be young.
-  return false;
-}
-
-jbyte* ConcurrentG1Refine::add_card_count(jbyte* card_ptr, int* count, bool* defer) {
-  unsigned new_card_num = ptr_2_card_num(card_ptr);
-  unsigned bucket = hash(new_card_num);
-  assert(0 <= bucket && bucket < _n_card_counts, "Bounds");
-
-  CardCountCacheEntry* count_ptr = &_card_counts[bucket];
-  CardEpochCacheEntry* epoch_ptr = &_card_epochs[bucket];
-
-  // We have to construct a new entry if we haven't updated the counts
-  // during the current period, or if the count was updated for a
-  // different card number.
-  unsigned int new_epoch = (unsigned int) _n_periods;
-  julong new_epoch_entry = make_epoch_entry(new_card_num, new_epoch);
-
-  while (true) {
-    // Fetch the previous epoch value
-    julong prev_epoch_entry = epoch_ptr->_value;
-    julong cas_res;
-
-    if (extract_epoch(prev_epoch_entry) != new_epoch) {
-      // This entry has not yet been updated during this period.
-      // Note: we update the epoch value atomically to ensure
-      // that there is only one winner that updates the cached
-      // card_ptr value even though all the refine threads share
-      // the same epoch value.
-
-      cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry,
-                                         (volatile jlong*)&epoch_ptr->_value,
-                                         (jlong) prev_epoch_entry);
-
-      if (cas_res == prev_epoch_entry) {
-        // We have successfully won the race to update the
-        // epoch and card_num value. Make it look like the
-        // count and eviction count were previously cleared.
-        count_ptr->_count = 1;
-        count_ptr->_evict_count = 0;
-        *count = 0;
-        // We can defer the processing of card_ptr
-        *defer = true;
-        return card_ptr;
-      }
-      // We did not win the race to update the epoch field, so some other
-      // thread must have done it. The value that gets returned by CAS
-      // should be the new epoch value.
-      assert(extract_epoch(cas_res) == new_epoch, "unexpected epoch");
-      // We could 'continue' here or just re-read the previous epoch value
-      prev_epoch_entry = epoch_ptr->_value;
-    }
-
-    // The epoch entry for card_ptr has been updated during this period.
-    unsigned old_card_num = extract_card_num(prev_epoch_entry);
-
-    // The card count that will be returned to caller
-    *count = count_ptr->_count;
-
-    // Are we updating the count for the same card?
-    if (new_card_num == old_card_num) {
-      // Same card - just update the count. We could have more than one
-      // thread racing to update count for the current card. It should be
-      // OK not to use a CAS as the only penalty should be some missed
-      // increments of the count which delays identifying the card as "hot".
-
-      if (*count < max_jubyte) count_ptr->_count++;
-      // We can defer the processing of card_ptr
-      *defer = true;
-      return card_ptr;
-    }
-
-    // Different card - evict old card info
-    if (count_ptr->_evict_count < max_jubyte) count_ptr->_evict_count++;
-    if (count_ptr->_evict_count > G1CardCountCacheExpandThreshold) {
-      // Trigger a resize the next time we clear
-      _expand_card_counts = true;
-    }
-
-    cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry,
-                                       (volatile jlong*)&epoch_ptr->_value,
-                                       (jlong) prev_epoch_entry);
-
-    if (cas_res == prev_epoch_entry) {
-      // We successfully updated the card num value in the epoch entry
-      count_ptr->_count = 0; // initialize counter for new card num
-      jbyte* old_card_ptr = card_num_2_ptr(old_card_num);
-
-      // Even though the region containg the card at old_card_num was not
-      // in the young list when old_card_num was recorded in the epoch
-      // cache it could have been added to the free list and subsequently
-      // added to the young list in the intervening time. See CR 6817995.
-      // We do not deal with this case here - it will be handled in
-      // HeapRegion::oops_on_card_seq_iterate_careful after it has been
-      // determined that the region containing the card has been allocated
-      // to, and it's safe to check the young type of the region.
-
-      // We do not want to defer processing of card_ptr in this case
-      // (we need to refine old_card_ptr and card_ptr)
-      *defer = false;
-      return old_card_ptr;
-    }
-    // Someone else beat us - try again.
-  }
-}
-
-jbyte* ConcurrentG1Refine::cache_insert(jbyte* card_ptr, bool* defer) {
-  int count;
-  jbyte* cached_ptr = add_card_count(card_ptr, &count, defer);
-  assert(cached_ptr != NULL, "bad cached card ptr");
-
-  // We've just inserted a card pointer into the card count cache
-  // and got back the card that we just inserted or (evicted) the
-  // previous contents of that count slot.
-
-  // The card we got back could be in a young region. When the
-  // returned card (if evicted) was originally inserted, we had
-  // determined that its containing region was not young. However
-  // it is possible for the region to be freed during a cleanup
-  // pause, then reallocated and tagged as young which will result
-  // in the returned card residing in a young region.
-  //
-  // We do not deal with this case here - the change from non-young
-  // to young could be observed at any time - it will be handled in
-  // HeapRegion::oops_on_card_seq_iterate_careful after it has been
-  // determined that the region containing the card has been allocated
-  // to.
-
-  // The card pointer we obtained from card count cache is not hot
-  // so do not store it in the cache; return it for immediate
-  // refining.
-  if (count < G1ConcRSHotCardLimit) {
-    return cached_ptr;
-  }
-
-  // Otherwise, the pointer we got from the _card_counts cache is hot.
-  jbyte* res = NULL;
-  MutexLockerEx x(HotCardCache_lock, Mutex::_no_safepoint_check_flag);
-  if (_n_hot == _hot_cache_size) {
-    res = _hot_cache[_hot_cache_idx];
-    _n_hot--;
-  }
-  // Now _n_hot < _hot_cache_size, and we can insert at _hot_cache_idx.
-  _hot_cache[_hot_cache_idx] = cached_ptr;
-  _hot_cache_idx++;
-  if (_hot_cache_idx == _hot_cache_size) _hot_cache_idx = 0;
-  _n_hot++;
-
-  // The card obtained from the hot card cache could be in a young
-  // region. See above on how this can happen.
-
-  return res;
-}
-
-void ConcurrentG1Refine::clean_up_cache(int worker_i,
-                                        G1RemSet* g1rs,
-                                        DirtyCardQueue* into_cset_dcq) {
-  assert(!use_cache(), "cache should be disabled");
-  int start_idx;
-
-  while ((start_idx = _hot_cache_par_claimed_idx) < _n_hot) { // read once
-    int end_idx = start_idx + _hot_cache_par_chunk_size;
-
-    if (start_idx ==
-        Atomic::cmpxchg(end_idx, &_hot_cache_par_claimed_idx, start_idx)) {
-      // The current worker has successfully claimed the chunk [start_idx..end_idx)
-      end_idx = MIN2(end_idx, _n_hot);
-      for (int i = start_idx; i < end_idx; i++) {
-        jbyte* entry = _hot_cache[i];
-        if (entry != NULL) {
-          if (g1rs->concurrentRefineOneCard(entry, worker_i, true)) {
-            // 'entry' contains references that point into the current
-            // collection set. We need to record 'entry' in the DCQS
-            // that's used for that purpose.
-            //
-            // The only time we care about recording cards that contain
-            // references that point into the collection set is during
-            // RSet updating while within an evacuation pause.
-            // In this case worker_i should be the id of a GC worker thread
-            assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
-            assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "incorrect worker id");
-            into_cset_dcq->enqueue(entry);
-          }
-        }
-      }
-    }
-  }
-}
-
-// The arrays used to hold the card counts and the epochs must have
-// a 1:1 correspondence. Hence they are allocated and freed together
-// Returns true if the allocations of both the counts and epochs
-// were successful; false otherwise.
-bool ConcurrentG1Refine::allocate_card_count_cache(size_t n,
-                                                   CardCountCacheEntry** counts,
-                                                   CardEpochCacheEntry** epochs) {
-  // We call the allocation/free routines directly for the counts
-  // and epochs arrays. The NEW_C_HEAP_ARRAY/FREE_C_HEAP_ARRAY
-  // macros call AllocateHeap and FreeHeap respectively.
-  // AllocateHeap will call vm_exit_out_of_memory in the event
-  // of an allocation failure and abort the JVM. With the
-  // _counts/epochs arrays we only need to abort the JVM if the
-  // initial allocation of these arrays fails.
-  //
-  // Additionally AllocateHeap/FreeHeap do some tracing of
-  // allocate/free calls so calling one without calling the
-  // other can cause inconsistencies in the tracing. So we
-  // call neither.
-
-  assert(*counts == NULL, "out param");
-  assert(*epochs == NULL, "out param");
-
-  size_t counts_size = n * sizeof(CardCountCacheEntry);
-  size_t epochs_size = n * sizeof(CardEpochCacheEntry);
-
-  *counts = (CardCountCacheEntry*) os::malloc(counts_size, mtGC);
-  if (*counts == NULL) {
-    // allocation was unsuccessful
-    return false;
-  }
-
-  *epochs = (CardEpochCacheEntry*) os::malloc(epochs_size, mtGC);
-  if (*epochs == NULL) {
-    // allocation was unsuccessful - free counts array
-    assert(*counts != NULL, "must be");
-    os::free(*counts, mtGC);
-    *counts = NULL;
-    return false;
-  }
-
-  // We successfully allocated both counts and epochs
-  return true;
-}
-
-// Returns true if the card counts/epochs cache was
-// successfully expanded; false otherwise.
-bool ConcurrentG1Refine::expand_card_count_cache(int cache_size_idx) {
-  // Can we expand the card count and epoch tables?
-  if (_n_card_counts < _max_n_card_counts) {
-    assert(cache_size_idx >= 0 && cache_size_idx  < MAX_CC_CACHE_INDEX, "oob");
-
-    size_t cache_size = _cc_cache_sizes[cache_size_idx];
-    // Make sure we don't go bigger than we will ever need
-    cache_size = MIN2(cache_size, _max_n_card_counts);
-
-    // Should we expand the card count and card epoch tables?
-    if (cache_size > _n_card_counts) {
-      // We have been asked to allocate new, larger, arrays for
-      // the card counts and the epochs. Attempt the allocation
-      // of both before we free the existing arrays in case
-      // the allocation is unsuccessful...
-      CardCountCacheEntry* counts = NULL;
-      CardEpochCacheEntry* epochs = NULL;
-
-      if (allocate_card_count_cache(cache_size, &counts, &epochs)) {
-        // Allocation was successful.
-        // We can just free the old arrays; we're
-        // not interested in preserving the contents
-        if (_card_counts != NULL) os::free(_card_counts, mtGC);
-        if (_card_epochs != NULL) os::free(_card_epochs, mtGC);
-
-        // Cache the size of the arrays and the index that got us there.
-        _n_card_counts = cache_size;
-        _cache_size_index = cache_size_idx;
-
-        _card_counts = counts;
-        _card_epochs = epochs;
-
-        // We successfully allocated/expanded the caches.
-        return true;
-      }
-    }
-  }
-
-  // We did not successfully expand the caches.
-  return false;
-}
-
-void ConcurrentG1Refine::clear_and_record_card_counts() {
-  if (G1ConcRSLogCacheSize == 0) {
-    return;
-  }
-
-  double start = os::elapsedTime();
-
-  if (_expand_card_counts) {
-    int new_idx = _cache_size_index + 1;
-
-    if (expand_card_count_cache(new_idx)) {
-      // Allocation was successful and  _n_card_counts has
-      // been updated to the new size. We only need to clear
-      // the epochs so we don't read a bogus epoch value
-      // when inserting a card into the hot card cache.
-      Copy::fill_to_bytes(&_card_epochs[0], _n_card_counts * sizeof(CardEpochCacheEntry));
-    }
-    _expand_card_counts = false;
-  }
-
-  int this_epoch = (int) _n_periods;
-  assert((this_epoch+1) <= max_jint, "to many periods");
-  // Update epoch
-  _n_periods++;
-  double cc_clear_time_ms = (os::elapsedTime() - start) * 1000;
-  _g1h->g1_policy()->phase_times()->record_cc_clear_time_ms(cc_clear_time_ms);
+int ConcurrentG1Refine::thread_num() {
+  int n_threads = (G1ConcRefinementThreads > 0) ? G1ConcRefinementThreads
+                                                : ParallelGCThreads;
+  return MAX2<int>(n_threads, 1);
 }
 
 void ConcurrentG1Refine::print_worker_threads_on(outputStream* st) const {
--- a/src/share/vm/gc_implementation/g1/concurrentG1Refine.hpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/concurrentG1Refine.hpp	Fri May 10 09:24:20 2013 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2013, 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
@@ -25,13 +25,15 @@
 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTG1REFINE_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTG1REFINE_HPP
 
+#include "gc_implementation/g1/g1HotCardCache.hpp"
 #include "memory/allocation.hpp"
-#include "memory/cardTableModRefBS.hpp"
 #include "runtime/thread.hpp"
 #include "utilities/globalDefinitions.hpp"
 
 // Forward decl
 class ConcurrentG1RefineThread;
+class G1CollectedHeap;
+class G1HotCardCache;
 class G1RemSet;
 
 class ConcurrentG1Refine: public CHeapObj<mtGC> {
@@ -61,141 +63,14 @@
 
   int _thread_threshold_step;
 
+  // We delay the refinement of 'hot' cards using the hot card cache.
+  G1HotCardCache _hot_card_cache;
+
   // Reset the threshold step value based of the current zone boundaries.
   void reset_threshold_step();
 
-  // The cache for card refinement.
-  bool   _use_cache;
-  bool   _def_use_cache;
-
-  size_t _n_periods;    // Used as clearing epoch
-
-  // An evicting cache of the number of times each card
-  // is accessed. Reduces, but does not eliminate, the amount
-  // of duplicated processing of dirty cards.
-
-  enum SomePrivateConstants {
-    epoch_bits           = 32,
-    card_num_shift       = epoch_bits,
-    epoch_mask           = AllBits,
-    card_num_mask        = AllBits,
-
-    // The initial cache size is approximately this fraction
-    // of a maximal cache (i.e. the size needed for all cards
-    // in the heap)
-    InitialCacheFraction = 512
-  };
-
-  const static julong card_num_mask_in_place =
-                        (julong) card_num_mask << card_num_shift;
-
-  typedef struct {
-    julong _value;      // |  card_num   |  epoch   |
-  } CardEpochCacheEntry;
-
-  julong make_epoch_entry(unsigned int card_num, unsigned int epoch) {
-    assert(0 <= card_num && card_num < _max_cards, "Bounds");
-    assert(0 <= epoch && epoch <= _n_periods, "must be");
-
-    return ((julong) card_num << card_num_shift) | epoch;
-  }
-
-  unsigned int extract_epoch(julong v) {
-    return (v & epoch_mask);
-  }
-
-  unsigned int extract_card_num(julong v) {
-    return (v & card_num_mask_in_place) >> card_num_shift;
-  }
-
-  typedef struct {
-    unsigned char _count;
-    unsigned char _evict_count;
-  } CardCountCacheEntry;
-
-  CardCountCacheEntry* _card_counts;
-  CardEpochCacheEntry* _card_epochs;
-
-  // The current number of buckets in the card count cache
-  size_t _n_card_counts;
-
-  // The number of cards for the entire reserved heap
-  size_t _max_cards;
-
-  // The max number of buckets for the card counts and epochs caches.
-  // This is the maximum that the counts and epochs will grow to.
-  // It is specified as a fraction or percentage of _max_cards using
-  // G1MaxHotCardCountSizePercent.
-  size_t _max_n_card_counts;
-
-  // Possible sizes of the cache: odd primes that roughly double in size.
-  // (See jvmtiTagMap.cpp).
-  enum {
-    MAX_CC_CACHE_INDEX = 15    // maximum index into the cache size array.
-  };
-
-  static size_t _cc_cache_sizes[MAX_CC_CACHE_INDEX];
-
-  // The index in _cc_cache_sizes corresponding to the size of
-  // _card_counts.
-  int _cache_size_index;
-
-  bool _expand_card_counts;
-
-  const jbyte* _ct_bot;
-
-  jbyte**      _hot_cache;
-  int          _hot_cache_size;
-  int          _n_hot;
-  int          _hot_cache_idx;
-
-  int          _hot_cache_par_chunk_size;
-  volatile int _hot_cache_par_claimed_idx;
-
-  // Needed to workaround 6817995
-  CardTableModRefBS* _ct_bs;
-  G1CollectedHeap*   _g1h;
-
-  // Helper routine for expand_card_count_cache().
-  // The arrays used to hold the card counts and the epochs must have
-  // a 1:1 correspondence. Hence they are allocated and freed together.
-  // Returns true if the allocations of both the counts and epochs
-  // were successful; false otherwise.
-  bool allocate_card_count_cache(size_t n,
-                                 CardCountCacheEntry** counts,
-                                 CardEpochCacheEntry** epochs);
-
-  // Expands the arrays that hold the card counts and epochs
-  // to the cache size at index. Returns true if the expansion/
-  // allocation was successful; false otherwise.
-  bool expand_card_count_cache(int index);
-
-  // hash a given key (index of card_ptr) with the specified size
-  static unsigned int hash(size_t key, size_t size) {
-    return (unsigned int) (key % size);
-  }
-
-  // hash a given key (index of card_ptr)
-  unsigned int hash(size_t key) {
-    return hash(key, _n_card_counts);
-  }
-
-  unsigned int ptr_2_card_num(jbyte* card_ptr) {
-    return (unsigned int) (card_ptr - _ct_bot);
-  }
-
-  jbyte* card_num_2_ptr(unsigned int card_num) {
-    return (jbyte*) (_ct_bot + card_num);
-  }
-
-  // Returns the count of this card after incrementing it.
-  jbyte* add_card_count(jbyte* card_ptr, int* count, bool* defer);
-
-  // Returns true if this card is in a young region
-  bool is_young_card(jbyte* card_ptr);
-
  public:
-  ConcurrentG1Refine();
+  ConcurrentG1Refine(G1CollectedHeap* g1h);
   ~ConcurrentG1Refine();
 
   void init(); // Accomplish some initialization that has to wait.
@@ -206,34 +81,6 @@
   // Iterate over the conc refine threads
   void threads_do(ThreadClosure *tc);
 
-  // If this is the first entry for the slot, writes into the cache and
-  // returns NULL.  If it causes an eviction, returns the evicted pointer.
-  // Otherwise, its a cache hit, and returns NULL.
-  jbyte* cache_insert(jbyte* card_ptr, bool* defer);
-
-  // Process the cached entries.
-  void clean_up_cache(int worker_i, G1RemSet* g1rs, DirtyCardQueue* into_cset_dcq);
-
-  // Set up for parallel processing of the cards in the hot cache
-  void clear_hot_cache_claimed_index() {
-    _hot_cache_par_claimed_idx = 0;
-  }
-
-  // Discard entries in the hot cache.
-  void clear_hot_cache() {
-    _hot_cache_idx = 0; _n_hot = 0;
-  }
-
-  bool hot_cache_is_empty() { return _n_hot == 0; }
-
-  bool use_cache() { return _use_cache; }
-  void set_use_cache(bool b) {
-    if (b) _use_cache = _def_use_cache;
-    else   _use_cache = false;
-  }
-
-  void clear_and_record_card_counts();
-
   static int thread_num();
 
   void print_worker_threads_on(outputStream* st) const;
@@ -250,6 +97,8 @@
   int worker_thread_num() const { return _n_worker_threads; }
 
   int thread_threshold_step() const { return _thread_threshold_step; }
+
+  G1HotCardCache* hot_card_cache() { return &_hot_card_cache; }
 };
 
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTG1REFINE_HPP
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1CardCounts.cpp	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,212 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc_implementation/g1/g1CardCounts.hpp"
+#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
+#include "gc_implementation/g1/g1CollectorPolicy.hpp"
+#include "gc_implementation/g1/g1GCPhaseTimes.hpp"
+#include "memory/cardTableModRefBS.hpp"
+#include "services/memTracker.hpp"
+#include "utilities/copy.hpp"
+
+void G1CardCounts::clear_range(size_t from_card_num, size_t to_card_num) {
+  if (has_count_table()) {
+    check_card_num(from_card_num,
+                   err_msg("from card num out of range: "SIZE_FORMAT, from_card_num));
+    assert(from_card_num < to_card_num,
+           err_msg("Wrong order? from: " SIZE_FORMAT ", to: "SIZE_FORMAT,
+                   from_card_num, to_card_num));
+    assert(to_card_num <= _committed_max_card_num,
+           err_msg("to card num out of range: "
+                   "to: "SIZE_FORMAT ", "
+                   "max: "SIZE_FORMAT,
+                   to_card_num, _committed_max_card_num));
+
+    to_card_num = MIN2(_committed_max_card_num, to_card_num);
+
+    Copy::fill_to_bytes(&_card_counts[from_card_num], (to_card_num - from_card_num));
+  }
+}
+
+G1CardCounts::G1CardCounts(G1CollectedHeap *g1h):
+  _g1h(g1h), _card_counts(NULL),
+  _reserved_max_card_num(0), _committed_max_card_num(0),
+  _committed_size(0) {}
+
+void G1CardCounts::initialize() {
+  assert(_g1h->max_capacity() > 0, "initialization order");
+  assert(_g1h->capacity() == 0, "initialization order");
+
+  if (G1ConcRSHotCardLimit > 0) {
+    // The max value we can store in the counts table is
+    // max_jubyte. Guarantee the value of the hot
+    // threshold limit is no more than this.
+    guarantee(G1ConcRSHotCardLimit <= max_jubyte, "sanity");
+
+    ModRefBarrierSet* bs = _g1h->mr_bs();
+    guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
+    _ct_bs = (CardTableModRefBS*)bs;
+    _ct_bot = _ct_bs->byte_for_const(_g1h->reserved_region().start());
+
+    // Allocate/Reserve the counts table
+    size_t reserved_bytes = _g1h->max_capacity();
+    _reserved_max_card_num = reserved_bytes >> CardTableModRefBS::card_shift;
+
+    size_t reserved_size = _reserved_max_card_num * sizeof(jbyte);
+    ReservedSpace rs(ReservedSpace::allocation_align_size_up(reserved_size));
+    if (!rs.is_reserved()) {
+      warning("Could not reserve enough space for the card counts table");
+      guarantee(!has_reserved_count_table(), "should be NULL");
+      return;
+    }
+
+    MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
+
+    _card_counts_storage.initialize(rs, 0);
+    _card_counts = (jubyte*) _card_counts_storage.low();
+  }
+}
+
+void G1CardCounts::resize(size_t heap_capacity) {
+  // Expand the card counts table to handle a heap with the given capacity.
+
+  if (!has_reserved_count_table()) {
+    // Don't expand if we failed to reserve the card counts table.
+    return;
+  }
+
+  assert(_committed_size ==
+         ReservedSpace::allocation_align_size_up(_committed_size),
+         err_msg("Unaligned? committed_size: " SIZE_FORMAT, _committed_size));
+
+  // Verify that the committed space for the card counts
+  // matches our committed max card num.
+  size_t prev_committed_size = _committed_size;
+  size_t prev_committed_card_num = prev_committed_size / sizeof(jbyte);
+  assert(prev_committed_card_num == _committed_max_card_num,
+         err_msg("Card mismatch: "
+                 "prev: " SIZE_FORMAT ", "
+                 "committed: "SIZE_FORMAT,
+                 prev_committed_card_num, _committed_max_card_num));
+
+  size_t new_size = (heap_capacity >> CardTableModRefBS::card_shift) * sizeof(jbyte);
+  size_t new_committed_size = ReservedSpace::allocation_align_size_up(new_size);
+  size_t new_committed_card_num =
+                MIN2(_reserved_max_card_num, new_committed_size / sizeof(jbyte));
+
+  if (_committed_max_card_num < new_committed_card_num) {
+    // we need to expand the backing store for the card counts
+    size_t expand_size = new_committed_size - prev_committed_size;
+
+    if (!_card_counts_storage.expand_by(expand_size)) {
+      warning("Card counts table backing store commit failure");
+      return;
+    }
+    assert(_card_counts_storage.committed_size() == new_committed_size,
+           "expansion commit failure");
+
+    _committed_size = new_committed_size;
+    _committed_max_card_num = new_committed_card_num;
+
+    clear_range(prev_committed_card_num, _committed_max_card_num);
+  }
+}
+
+uint G1CardCounts::add_card_count(jbyte* card_ptr) {
+  // Returns the number of times the card has been refined.
+  // If we failed to reserve/commit the counts table, return 0.
+  // If card_ptr is beyond the committed end of the counts table,
+  // return 0.
+  // Otherwise return the actual count.
+  // Unless G1ConcRSHotCardLimit has been set appropriately,
+  // returning 0 will result in the card being considered
+  // cold and will be refined immediately.
+  uint count = 0;
+  if (has_count_table()) {
+    size_t card_num = ptr_2_card_num(card_ptr);
+    if (card_num < _committed_max_card_num) {
+      count = (uint) _card_counts[card_num];
+      if (count < G1ConcRSHotCardLimit) {
+        _card_counts[card_num] += 1;
+      }
+      assert(_card_counts[card_num] <= G1ConcRSHotCardLimit,
+             err_msg("Refinement count overflow? "
+                     "new count: "UINT32_FORMAT,
+                     (uint) _card_counts[card_num]));
+    }
+  }
+  return count;
+}
+
+bool G1CardCounts::is_hot(uint count) {
+  return (count >= G1ConcRSHotCardLimit);
+}
+
+void G1CardCounts::clear_region(HeapRegion* hr) {
+  assert(!hr->isHumongous(), "Should have been cleared");
+  if (has_count_table()) {
+    HeapWord* bottom = hr->bottom();
+
+    // We use the last address in hr as hr could be the
+    // last region in the heap. In which case trying to find
+    // the card for hr->end() will be an OOB accesss to the
+    // card table.
+    HeapWord* last = hr->end() - 1;
+    assert(_g1h->g1_committed().contains(last),
+           err_msg("last not in committed: "
+                   "last: " PTR_FORMAT ", "
+                   "committed: [" PTR_FORMAT ", " PTR_FORMAT ")",
+                   last,
+                   _g1h->g1_committed().start(),
+                   _g1h->g1_committed().end()));
+
+    const jbyte* from_card_ptr = _ct_bs->byte_for_const(bottom);
+    const jbyte* last_card_ptr = _ct_bs->byte_for_const(last);
+
+#ifdef ASSERT
+    HeapWord* start_addr = _ct_bs->addr_for(from_card_ptr);
+    assert(start_addr == hr->bottom(), "alignment");
+    HeapWord* last_addr = _ct_bs->addr_for(last_card_ptr);
+    assert((last_addr + CardTableModRefBS::card_size_in_words) == hr->end(), "alignment");
+#endif // ASSERT
+
+    // Clear the counts for the (exclusive) card range.
+    size_t from_card_num = ptr_2_card_num(from_card_ptr);
+    size_t to_card_num = ptr_2_card_num(last_card_ptr) + 1;
+    clear_range(from_card_num, to_card_num);
+  }
+}
+
+void G1CardCounts::clear_all() {
+  assert(SafepointSynchronize::is_at_safepoint(), "don't call this otherwise");
+  clear_range((size_t)0, _committed_max_card_num);
+}
+
+G1CardCounts::~G1CardCounts() {
+  if (has_reserved_count_table()) {
+    _card_counts_storage.release();
+  }
+}
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1CardCounts.hpp	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP
+#define SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP
+
+#include "memory/allocation.hpp"
+#include "runtime/virtualspace.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+class CardTableModRefBS;
+class G1CollectedHeap;
+class HeapRegion;
+
+// Table to track the number of times a card has been refined. Once
+// a card has been refined a certain number of times, it is
+// considered 'hot' and its refinement is delayed by inserting the
+// card into the hot card cache. The card will then be refined when
+// it is evicted from the hot card cache, or when the hot card cache
+// is 'drained' during the next evacuation pause.
+
+class G1CardCounts: public CHeapObj<mtGC> {
+  G1CollectedHeap* _g1h;
+
+  // The table of counts
+  jubyte* _card_counts;
+
+  // Max capacity of the reserved space for the counts table
+  size_t _reserved_max_card_num;
+
+  // Max capacity of the committed space for the counts table
+  size_t _committed_max_card_num;
+
+  // Size of committed space for the counts table
+  size_t _committed_size;
+
+  // CardTable bottom.
+  const jbyte* _ct_bot;
+
+  // Barrier set
+  CardTableModRefBS* _ct_bs;
+
+  // The virtual memory backing the counts table
+  VirtualSpace _card_counts_storage;
+
+  // Returns true if the card counts table has been reserved.
+  bool has_reserved_count_table() { return _card_counts != NULL; }
+
+  // Returns true if the card counts table has been reserved and committed.
+  bool has_count_table() {
+    return has_reserved_count_table() && _committed_max_card_num > 0;
+  }
+
+  void check_card_num(size_t card_num, const char* msg) {
+    assert(card_num >= 0 && card_num < _committed_max_card_num, msg);
+  }
+
+  size_t ptr_2_card_num(const jbyte* card_ptr) {
+    assert(card_ptr >= _ct_bot,
+           err_msg("Inavalied card pointer: "
+                   "card_ptr: " PTR_FORMAT ", "
+                   "_ct_bot: " PTR_FORMAT,
+                   card_ptr, _ct_bot));
+    size_t card_num = pointer_delta(card_ptr, _ct_bot, sizeof(jbyte));
+    check_card_num(card_num,
+                   err_msg("card pointer out of range: " PTR_FORMAT, card_ptr));
+    return card_num;
+  }
+
+  jbyte* card_num_2_ptr(size_t card_num) {
+    check_card_num(card_num,
+                   err_msg("card num out of range: "SIZE_FORMAT, card_num));
+    return (jbyte*) (_ct_bot + card_num);
+  }
+
+  // Clear the counts table for the given (exclusive) index range.
+  void clear_range(size_t from_card_num, size_t to_card_num);
+
+ public:
+  G1CardCounts(G1CollectedHeap* g1h);
+  ~G1CardCounts();
+
+  void initialize();
+
+  // Resize the committed space for the card counts table in
+  // response to a resize of the committed space for the heap.
+  void resize(size_t heap_capacity);
+
+  // Increments the refinement count for the given card.
+  // Returns the pre-increment count value.
+  uint add_card_count(jbyte* card_ptr);
+
+  // Returns true if the given count is high enough to be considered
+  // 'hot'; false otherwise.
+  bool is_hot(uint count);
+
+  // Clears the card counts for the cards spanned by the region
+  void clear_region(HeapRegion* hr);
+
+  // Clear the entire card counts table during GC.
+  // Updates the policy stats with the duration.
+  void clear_all();
+};
+
+#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Fri May 10 09:24:20 2013 +0200
@@ -96,7 +96,7 @@
     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
   {}
   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
-    bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
+    bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
     // This path is executed by the concurrent refine or mutator threads,
     // concurrently, and so we do not care if card_ptr contains references
     // that point into the collection set.
@@ -1452,9 +1452,10 @@
         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
       }
 
-      if (_cg1r->use_cache()) {
-        _cg1r->clear_and_record_card_counts();
-        _cg1r->clear_hot_cache();
+      G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
+      if (hot_card_cache->use_cache()) {
+        hot_card_cache->reset_card_counts();
+        hot_card_cache->reset_hot_cache();
       }
 
       // Rebuild remembered sets of all regions.
@@ -1767,6 +1768,8 @@
   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
   // Tell the BOT about the update.
   _bot_shared->resize(_g1_committed.word_size());
+  // Tell the hot card cache about the update
+  _cg1r->hot_card_cache()->resize_card_counts(capacity());
 }
 
 bool G1CollectedHeap::expand(size_t expand_bytes) {
@@ -1843,33 +1846,32 @@
     ReservedSpace::page_align_size_down(shrink_bytes);
   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
                                          HeapRegion::GrainBytes);
-  uint num_regions_deleted = 0;
-  MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
+  uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
+
+  uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
   HeapWord* old_end = (HeapWord*) _g1_storage.high();
-  assert(mr.end() == old_end, "post-condition");
+  size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
 
   ergo_verbose3(ErgoHeapSizing,
                 "shrink the heap",
                 ergo_format_byte("requested shrinking amount")
                 ergo_format_byte("aligned shrinking amount")
                 ergo_format_byte("attempted shrinking amount"),
-                shrink_bytes, aligned_shrink_bytes, mr.byte_size());
-  if (mr.byte_size() > 0) {
+                shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
+  if (num_regions_removed > 0) {
+    _g1_storage.shrink_by(shrunk_bytes);
+    HeapWord* new_end = (HeapWord*) _g1_storage.high();
+
     if (_hr_printer.is_active()) {
-      HeapWord* curr = mr.end();
-      while (curr > mr.start()) {
+      HeapWord* curr = old_end;
+      while (curr > new_end) {
         HeapWord* curr_end = curr;
         curr -= HeapRegion::GrainWords;
         _hr_printer.uncommit(curr, curr_end);
       }
-      assert(curr == mr.start(), "post-condition");
     }
 
-    _g1_storage.shrink_by(mr.byte_size());
-    HeapWord* new_end = (HeapWord*) _g1_storage.high();
-    assert(mr.start() == new_end, "post-condition");
-
-    _expansion_regions += num_regions_deleted;
+    _expansion_regions += num_regions_removed;
     update_committed_space(old_end, new_end);
     HeapRegionRemSet::shrink_heap(n_regions());
     g1_policy()->record_new_heap_size(n_regions());
@@ -2000,7 +2002,7 @@
   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
 
-  _cg1r = new ConcurrentG1Refine();
+  _cg1r = new ConcurrentG1Refine(this);
 
   // Reserve the maximum.
 
@@ -2061,6 +2063,9 @@
                   (HeapWord*) _g1_reserved.end(),
                   _expansion_regions);
 
+  // Do later initialization work for concurrent refinement.
+  _cg1r->init();
+
   // 6843694 - ensure that the maximum region index can fit
   // in the remembered set structures.
   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
@@ -2078,20 +2083,20 @@
 
   _g1h = this;
 
-   _in_cset_fast_test_length = max_regions();
-   _in_cset_fast_test_base =
+  _in_cset_fast_test_length = max_regions();
+  _in_cset_fast_test_base =
                    NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
 
-   // We're biasing _in_cset_fast_test to avoid subtracting the
-   // beginning of the heap every time we want to index; basically
-   // it's the same with what we do with the card table.
-   _in_cset_fast_test = _in_cset_fast_test_base -
+  // We're biasing _in_cset_fast_test to avoid subtracting the
+  // beginning of the heap every time we want to index; basically
+  // it's the same with what we do with the card table.
+  _in_cset_fast_test = _in_cset_fast_test_base -
                ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
 
-   // Clear the _cset_fast_test bitmap in anticipation of adding
-   // regions to the incremental collection set for the first
-   // evacuation pause.
-   clear_cset_fast_test();
+  // Clear the _cset_fast_test bitmap in anticipation of adding
+  // regions to the incremental collection set for the first
+  // evacuation pause.
+  clear_cset_fast_test();
 
   // Create the ConcurrentMark data structure and thread.
   // (Must do this late, so that "max_regions" is defined.)
@@ -2153,9 +2158,6 @@
   // counts and that mechanism.
   SpecializationStats::clear();
 
-  // Do later initialization work for concurrent refinement.
-  _cg1r->init();
-
   // 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.
@@ -2314,7 +2316,8 @@
                                                  bool concurrent,
                                                  int worker_i) {
   // Clean cards in the hot card cache
-  concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
+  G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
+  hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
 
   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
   int n_completed_buffers = 0;
@@ -5604,8 +5607,11 @@
   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
 
   g1_rem_set()->prepare_for_oops_into_collection_set_do();
-  concurrent_g1_refine()->set_use_cache(false);
-  concurrent_g1_refine()->clear_hot_cache_claimed_index();
+
+  // Disable the hot card cache.
+  G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
+  hot_card_cache->reset_hot_cache_claimed_index();
+  hot_card_cache->set_use_cache(false);
 
   uint n_workers;
   if (G1CollectedHeap::use_parallel_gc_threads()) {
@@ -5687,8 +5693,11 @@
   release_gc_alloc_regions(n_workers);
   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
 
-  concurrent_g1_refine()->clear_hot_cache();
-  concurrent_g1_refine()->set_use_cache(true);
+  // Reset and re-enable the hot card cache.
+  // Note the counts for the cards in the regions in the
+  // collection set are reset when the collection set is freed.
+  hot_card_cache->reset_hot_cache();
+  hot_card_cache->set_use_cache(true);
 
   finalize_for_evac_failure();
 
@@ -5750,6 +5759,12 @@
   assert(!hr->is_empty(), "the region should not be empty");
   assert(free_list != NULL, "pre-condition");
 
+  // Clear the card counts for this region.
+  // Note: we only need to do this if the region is not young
+  // (since we don't refine cards in young regions).
+  if (!hr->is_young()) {
+    _cg1r->hot_card_cache()->reset_card_counts(hr);
+  }
   *pre_used += hr->used();
   hr->hr_clear(par, true /* clear_space */);
   free_list->add_as_head(hr);
--- a/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Fri May 10 09:24:20 2013 +0200
@@ -309,7 +309,8 @@
 
 void G1CollectorPolicy::initialize_flags() {
   set_min_alignment(HeapRegion::GrainBytes);
-  set_max_alignment(GenRemSet::max_alignment_constraint(rem_set_name()));
+  size_t card_table_alignment = GenRemSet::max_alignment_constraint(rem_set_name());
+  set_max_alignment(MAX2(card_table_alignment, min_alignment()));
   if (SurvivorRatio < 1) {
     vm_exit_during_initialization("Invalid survivor ratio specified");
   }
--- a/src/share/vm/gc_implementation/g1/g1GCPhaseTimes.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/g1GCPhaseTimes.cpp	Fri May 10 09:24:20 2013 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 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
@@ -155,11 +155,6 @@
 
 G1GCPhaseTimes::G1GCPhaseTimes(uint max_gc_threads) :
   _max_gc_threads(max_gc_threads),
-  _min_clear_cc_time_ms(-1.0),
-  _max_clear_cc_time_ms(-1.0),
-  _cur_clear_cc_time_ms(0.0),
-  _cum_clear_cc_time_ms(0.0),
-  _num_cc_clears(0L),
   _last_gc_worker_start_times_ms(_max_gc_threads, "%.1lf", false),
   _last_ext_root_scan_times_ms(_max_gc_threads, "%.1lf"),
   _last_satb_filtering_times_ms(_max_gc_threads, "%.1lf"),
@@ -212,11 +207,11 @@
     _last_gc_worker_times_ms.set(i, worker_time);
 
     double worker_known_time = _last_ext_root_scan_times_ms.get(i) +
-      _last_satb_filtering_times_ms.get(i) +
-      _last_update_rs_times_ms.get(i) +
-      _last_scan_rs_times_ms.get(i) +
-      _last_obj_copy_times_ms.get(i) +
-      _last_termination_times_ms.get(i);
+                               _last_satb_filtering_times_ms.get(i) +
+                               _last_update_rs_times_ms.get(i) +
+                               _last_scan_rs_times_ms.get(i) +
+                               _last_obj_copy_times_ms.get(i) +
+                               _last_termination_times_ms.get(i);
 
     double worker_other_time = worker_time - worker_known_time;
     _last_gc_worker_other_times_ms.set(i, worker_other_time);
@@ -285,15 +280,6 @@
   }
   print_stats(1, "Code Root Fixup", _cur_collection_code_root_fixup_time_ms);
   print_stats(1, "Clear CT", _cur_clear_ct_time_ms);
-  if (Verbose && G1Log::finest()) {
-    print_stats(1, "Cur Clear CC", _cur_clear_cc_time_ms);
-    print_stats(1, "Cum Clear CC", _cum_clear_cc_time_ms);
-    print_stats(1, "Min Clear CC", _min_clear_cc_time_ms);
-    print_stats(1, "Max Clear CC", _max_clear_cc_time_ms);
-    if (_num_cc_clears > 0) {
-      print_stats(1, "Avg Clear CC", _cum_clear_cc_time_ms / ((double)_num_cc_clears));
-    }
-  }
   double misc_time_ms = pause_time_sec * MILLIUNITS - accounted_time_ms();
   print_stats(1, "Other", misc_time_ms);
   if (_cur_verify_before_time_ms > 0.0) {
@@ -311,19 +297,3 @@
     print_stats(2, "Verify After", _cur_verify_after_time_ms);
   }
 }
-
-void G1GCPhaseTimes::record_cc_clear_time_ms(double ms) {
-  if (!(Verbose && G1Log::finest())) {
-    return;
-  }
-
-  if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms) {
-    _min_clear_cc_time_ms = ms;
-  }
-  if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms) {
-    _max_clear_cc_time_ms = ms;
-  }
-  _cur_clear_cc_time_ms = ms;
-  _cum_clear_cc_time_ms += ms;
-  _num_cc_clears++;
-}
--- a/src/share/vm/gc_implementation/g1/g1GCPhaseTimes.hpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/g1GCPhaseTimes.hpp	Fri May 10 09:24:20 2013 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 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
@@ -133,13 +133,6 @@
   double _cur_ref_proc_time_ms;
   double _cur_ref_enq_time_ms;
 
-  // Card Table Count Cache stats
-  double _min_clear_cc_time_ms;         // min
-  double _max_clear_cc_time_ms;         // max
-  double _cur_clear_cc_time_ms;         // clearing time during current pause
-  double _cum_clear_cc_time_ms;         // cummulative clearing time
-  jlong  _num_cc_clears;                // number of times the card count cache has been cleared
-
   double _cur_collection_start_sec;
   double _root_region_scan_wait_time_ms;
 
@@ -227,8 +220,6 @@
     _root_region_scan_wait_time_ms = time_ms;
   }
 
-  void record_cc_clear_time_ms(double ms);
-
   void record_young_free_cset_time_ms(double time_ms) {
     _recorded_young_free_cset_time_ms = time_ms;
   }
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1HotCardCache.cpp	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,148 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc_implementation/g1/dirtyCardQueue.hpp"
+#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
+#include "gc_implementation/g1/g1HotCardCache.hpp"
+#include "gc_implementation/g1/g1RemSet.hpp"
+#include "gc_implementation/g1/heapRegion.hpp"
+#include "runtime/atomic.hpp"
+
+G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h):
+  _g1h(g1h), _hot_cache(NULL), _use_cache(false), _card_counts(g1h) {}
+
+void G1HotCardCache::initialize() {
+  if (default_use_cache()) {
+    _use_cache = true;
+
+    _hot_cache_size = (1 << G1ConcRSLogCacheSize);
+    _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size, mtGC);
+
+    _n_hot = 0;
+    _hot_cache_idx = 0;
+
+    // For refining the cards in the hot cache in parallel
+    int n_workers = (ParallelGCThreads > 0 ?
+                        _g1h->workers()->total_workers() : 1);
+    _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / n_workers);
+    _hot_cache_par_claimed_idx = 0;
+
+    _card_counts.initialize();
+  }
+}
+
+G1HotCardCache::~G1HotCardCache() {
+  if (default_use_cache()) {
+    assert(_hot_cache != NULL, "Logic");
+    FREE_C_HEAP_ARRAY(jbyte*, _hot_cache, mtGC);
+  }
+}
+
+jbyte* G1HotCardCache::insert(jbyte* card_ptr) {
+  uint count = _card_counts.add_card_count(card_ptr);
+  if (!_card_counts.is_hot(count)) {
+    // The card is not hot so do not store it in the cache;
+    // return it for immediate refining.
+    return card_ptr;
+  }
+
+  // Otherwise, the card is hot.
+  jbyte* res = NULL;
+  MutexLockerEx x(HotCardCache_lock, Mutex::_no_safepoint_check_flag);
+  if (_n_hot == _hot_cache_size) {
+    res = _hot_cache[_hot_cache_idx];
+    _n_hot--;
+  }
+
+  // Now _n_hot < _hot_cache_size, and we can insert at _hot_cache_idx.
+  _hot_cache[_hot_cache_idx] = card_ptr;
+  _hot_cache_idx++;
+
+  if (_hot_cache_idx == _hot_cache_size) {
+    // Wrap around
+    _hot_cache_idx = 0;
+  }
+  _n_hot++;
+
+  return res;
+}
+
+void G1HotCardCache::drain(int worker_i,
+                           G1RemSet* g1rs,
+                           DirtyCardQueue* into_cset_dcq) {
+  if (!default_use_cache()) {
+    assert(_hot_cache == NULL, "Logic");
+    return;
+  }
+
+  assert(_hot_cache != NULL, "Logic");
+  assert(!use_cache(), "cache should be disabled");
+  int start_idx;
+
+  while ((start_idx = _hot_cache_par_claimed_idx) < _n_hot) { // read once
+    int end_idx = start_idx + _hot_cache_par_chunk_size;
+
+    if (start_idx ==
+        Atomic::cmpxchg(end_idx, &_hot_cache_par_claimed_idx, start_idx)) {
+      // The current worker has successfully claimed the chunk [start_idx..end_idx)
+      end_idx = MIN2(end_idx, _n_hot);
+      for (int i = start_idx; i < end_idx; i++) {
+        jbyte* card_ptr = _hot_cache[i];
+        if (card_ptr != NULL) {
+          if (g1rs->refine_card(card_ptr, worker_i, true)) {
+            // The part of the heap spanned by the card contains references
+            // that point into the current collection set.
+            // We need to record the card pointer in the DirtyCardQueueSet
+            // that we use for such cards.
+            //
+            // The only time we care about recording cards that contain
+            // references that point into the collection set is during
+            // RSet updating while within an evacuation pause.
+            // In this case worker_i should be the id of a GC worker thread
+            assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");
+            assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads),
+                   err_msg("incorrect worker id: "INT32_FORMAT, worker_i));
+
+            into_cset_dcq->enqueue(card_ptr);
+          }
+        }
+      }
+    }
+  }
+  // The existing entries in the hot card cache, which were just refined
+  // above, are discarded prior to re-enabling the cache near the end of the GC.
+}
+
+void G1HotCardCache::resize_card_counts(size_t heap_capacity) {
+  _card_counts.resize(heap_capacity);
+}
+
+void G1HotCardCache::reset_card_counts(HeapRegion* hr) {
+  _card_counts.clear_region(hr);
+}
+
+void G1HotCardCache::reset_card_counts() {
+  _card_counts.clear_all();
+}
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1HotCardCache.hpp	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP
+#define SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP
+
+#include "gc_implementation/g1/g1_globals.hpp"
+#include "gc_implementation/g1/g1CardCounts.hpp"
+#include "memory/allocation.hpp"
+#include "runtime/safepoint.hpp"
+#include "runtime/thread.inline.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+class DirtyCardQueue;
+class G1CollectedHeap;
+class G1RemSet;
+class HeapRegion;
+
+// An evicting cache of cards that have been logged by the G1 post
+// write barrier. Placing a card in the cache delays the refinement
+// of the card until the card is evicted, or the cache is drained
+// during the next evacuation pause.
+//
+// The first thing the G1 post write barrier does is to check whether
+// the card containing the updated pointer is already dirty and, if
+// so, skips the remaining code in the barrier.
+//
+// Delaying the refinement of a card will make the card fail the
+// first is_dirty check in the write barrier, skipping the remainder
+// of the write barrier.
+//
+// This can significantly reduce the overhead of the write barrier
+// code, increasing throughput.
+
+class G1HotCardCache: public CHeapObj<mtGC> {
+  G1CollectedHeap*   _g1h;
+
+  // The card cache table
+  jbyte**      _hot_cache;
+
+  int          _hot_cache_size;
+  int          _n_hot;
+  int          _hot_cache_idx;
+
+  int          _hot_cache_par_chunk_size;
+  volatile int _hot_cache_par_claimed_idx;
+
+  bool         _use_cache;
+
+  G1CardCounts _card_counts;
+
+  bool default_use_cache() const {
+    return (G1ConcRSLogCacheSize > 0);
+  }
+
+ public:
+  G1HotCardCache(G1CollectedHeap* g1h);
+  ~G1HotCardCache();
+
+  void initialize();
+
+  bool use_cache() { return _use_cache; }
+
+  void set_use_cache(bool b) {
+    _use_cache = (b ? default_use_cache() : false);
+  }
+
+  // Returns the card to be refined or NULL.
+  //
+  // Increments the count for given the card. if the card is not 'hot',
+  // it is returned for immediate refining. Otherwise the card is
+  // added to the hot card cache.
+  // If there is enough room in the hot card cache for the card we're
+  // adding, NULL is returned and no further action in needed.
+  // If we evict a card from the cache to make room for the new card,
+  // the evicted card is then returned for refinement.
+  jbyte* insert(jbyte* card_ptr);
+
+  // Refine the cards that have delayed as a result of
+  // being in the cache.
+  void drain(int worker_i, G1RemSet* g1rs, DirtyCardQueue* into_cset_dcq);
+
+  // Set up for parallel processing of the cards in the hot cache
+  void reset_hot_cache_claimed_index() {
+    _hot_cache_par_claimed_idx = 0;
+  }
+
+  // Resets the hot card cache and discards the entries.
+  void reset_hot_cache() {
+    assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");
+    assert(Thread::current()->is_VM_thread(), "Current thread should be the VMthread");
+    _hot_cache_idx = 0; _n_hot = 0;
+  }
+
+  bool hot_cache_is_empty() { return _n_hot == 0; }
+
+  // Resizes the card counts table to match the given capacity
+  void resize_card_counts(size_t heap_capacity);
+
+  // Zeros the values in the card counts table for entire committed heap
+  void reset_card_counts();
+
+  // Zeros the values in the card counts table for the given region
+  void reset_card_counts(HeapRegion* hr);
+};
+
+#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1HOTCARDCACHE_HPP
--- a/src/share/vm/gc_implementation/g1/g1RemSet.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/g1RemSet.cpp	Fri May 10 09:24:20 2013 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2013, 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
@@ -29,6 +29,7 @@
 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
+#include "gc_implementation/g1/g1HotCardCache.hpp"
 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
 #include "gc_implementation/g1/g1RemSet.inline.hpp"
@@ -247,7 +248,7 @@
     assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
     assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");
 
-    if (_g1rs->concurrentRefineOneCard(card_ptr, worker_i, true)) {
+    if (_g1rs->refine_card(card_ptr, worker_i, true)) {
       // 'card_ptr' contains references that point into the collection
       // set. We need to record the card in the DCQS
       // (G1CollectedHeap::into_cset_dirty_card_queue_set())
@@ -288,9 +289,6 @@
 #if CARD_REPEAT_HISTO
   ct_freq_update_histo_and_reset();
 #endif
-  if (worker_i == 0) {
-    _cg1r->clear_and_record_card_counts();
-  }
 
   // We cache the value of 'oc' closure into the appropriate slot in the
   // _cset_rs_update_cl for this worker
@@ -396,7 +394,7 @@
     //   RSet updating,
     // * the post-write barrier shouldn't be logging updates to young
     //   regions (but there is a situation where this can happen - see
-    //   the comment in G1RemSet::concurrentRefineOneCard below -
+    //   the comment in G1RemSet::refine_card() below -
     //   that should not be applicable here), and
     // * during actual RSet updating, the filtering of cards in young
     //   regions in HeapRegion::oops_on_card_seq_iterate_careful is
@@ -502,8 +500,6 @@
                                        claim_val);
 }
 
-
-
 G1TriggerClosure::G1TriggerClosure() :
   _triggered(false) { }
 
@@ -524,13 +520,91 @@
   _record_refs_into_cset(record_refs_into_cset),
   _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
 
-bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
-                                                   bool check_for_refs_into_cset) {
+// Returns true if the given card contains references that point
+// into the collection set, if we're checking for such references;
+// false otherwise.
+
+bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i,
+                           bool check_for_refs_into_cset) {
+
+  // If the card is no longer dirty, nothing to do.
+  if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
+    // No need to return that this card contains refs that point
+    // into the collection set.
+    return false;
+  }
+
   // Construct the region representing the card.
   HeapWord* start = _ct_bs->addr_for(card_ptr);
   // And find the region containing it.
   HeapRegion* r = _g1->heap_region_containing(start);
-  assert(r != NULL, "unexpected null");
+  if (r == NULL) {
+    // Again no need to return that this card contains refs that
+    // point into the collection set.
+    return false;  // Not in the G1 heap (might be in perm, for example.)
+  }
+
+  // Why do we have to check here whether a card is on a young region,
+  // given that we dirty young regions and, as a result, the
+  // post-barrier is supposed to filter them out and never to enqueue
+  // them? When we allocate a new region as the "allocation region" we
+  // actually dirty its cards after we release the lock, since card
+  // dirtying while holding the lock was a performance bottleneck. So,
+  // as a result, it is possible for other threads to actually
+  // allocate objects in the region (after the acquire the lock)
+  // before all the cards on the region are dirtied. This is unlikely,
+  // and it doesn't happen often, but it can happen. So, the extra
+  // check below filters out those cards.
+  if (r->is_young()) {
+    return false;
+  }
+
+  // While we are processing RSet buffers during the collection, we
+  // actually don't want to scan any cards on the collection set,
+  // since we don't want to update remebered sets with entries that
+  // point into the collection set, given that live objects from the
+  // collection set are about to move and such entries will be stale
+  // very soon. This change also deals with a reliability issue which
+  // involves scanning a card in the collection set and coming across
+  // an array that was being chunked and looking malformed. Note,
+  // however, that if evacuation fails, we have to scan any objects
+  // that were not moved and create any missing entries.
+  if (r->in_collection_set()) {
+    return false;
+  }
+
+  // The result from the hot card cache insert call is either:
+  //   * pointer to the current card
+  //     (implying that the current card is not 'hot'),
+  //   * null
+  //     (meaning we had inserted the card ptr into the "hot" card cache,
+  //     which had some headroom),
+  //   * a pointer to a "hot" card that was evicted from the "hot" cache.
+  //
+
+  G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
+  if (hot_card_cache->use_cache()) {
+    assert(!check_for_refs_into_cset, "sanity");
+    assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
+
+    card_ptr = hot_card_cache->insert(card_ptr);
+    if (card_ptr == NULL) {
+      // There was no eviction. Nothing to do.
+      return false;
+    }
+
+    start = _ct_bs->addr_for(card_ptr);
+    r = _g1->heap_region_containing(start);
+    if (r == NULL) {
+      // Not in the G1 heap
+      return false;
+    }
+
+    // Checking whether the region we got back from the cache
+    // is young here is inappropriate. The region could have been
+    // freed, reallocated and tagged as young while in the cache.
+    // Hence we could see its young type change at any time.
+  }
 
   // Don't use addr_for(card_ptr + 1) which can ask for
   // a card beyond the heap.  This is not safe without a perm
@@ -610,140 +684,17 @@
     _conc_refine_cards++;
   }
 
-  return trigger_cl.triggered();
-}
+  // This gets set to true if the card being refined has
+  // references that point into the collection set.
+  bool has_refs_into_cset = trigger_cl.triggered();
 
-bool G1RemSet::concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
-                                              bool check_for_refs_into_cset) {
-  // If the card is no longer dirty, nothing to do.
-  if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
-    // No need to return that this card contains refs that point
-    // into the collection set.
-    return false;
-  }
+  // We should only be detecting that the card contains references
+  // that point into the collection set if the current thread is
+  // a GC worker thread.
+  assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
+           "invalid result at non safepoint");
 
-  // Construct the region representing the card.
-  HeapWord* start = _ct_bs->addr_for(card_ptr);
-  // And find the region containing it.
-  HeapRegion* r = _g1->heap_region_containing(start);
-  if (r == NULL) {
-    // Again no need to return that this card contains refs that
-    // point into the collection set.
-    return false;  // Not in the G1 heap (might be in perm, for example.)
-  }
-  // Why do we have to check here whether a card is on a young region,
-  // given that we dirty young regions and, as a result, the
-  // post-barrier is supposed to filter them out and never to enqueue
-  // them? When we allocate a new region as the "allocation region" we
-  // actually dirty its cards after we release the lock, since card
-  // dirtying while holding the lock was a performance bottleneck. So,
-  // as a result, it is possible for other threads to actually
-  // allocate objects in the region (after the acquire the lock)
-  // before all the cards on the region are dirtied. This is unlikely,
-  // and it doesn't happen often, but it can happen. So, the extra
-  // check below filters out those cards.
-  if (r->is_young()) {
-    return false;
-  }
-  // While we are processing RSet buffers during the collection, we
-  // actually don't want to scan any cards on the collection set,
-  // since we don't want to update remebered sets with entries that
-  // point into the collection set, given that live objects from the
-  // collection set are about to move and such entries will be stale
-  // very soon. This change also deals with a reliability issue which
-  // involves scanning a card in the collection set and coming across
-  // an array that was being chunked and looking malformed. Note,
-  // however, that if evacuation fails, we have to scan any objects
-  // that were not moved and create any missing entries.
-  if (r->in_collection_set()) {
-    return false;
-  }
-
-  // Should we defer processing the card?
-  //
-  // Previously the result from the insert_cache call would be
-  // either card_ptr (implying that card_ptr was currently "cold"),
-  // null (meaning we had inserted the card ptr into the "hot"
-  // cache, which had some headroom), or a "hot" card ptr
-  // extracted from the "hot" cache.
-  //
-  // Now that the _card_counts cache in the ConcurrentG1Refine
-  // instance is an evicting hash table, the result we get back
-  // could be from evicting the card ptr in an already occupied
-  // bucket (in which case we have replaced the card ptr in the
-  // bucket with card_ptr and "defer" is set to false). To avoid
-  // having a data structure (updates to which would need a lock)
-  // to hold these unprocessed dirty cards, we need to immediately
-  // process card_ptr. The actions needed to be taken on return
-  // from cache_insert are summarized in the following table:
-  //
-  // res      defer   action
-  // --------------------------------------------------------------
-  // null     false   card evicted from _card_counts & replaced with
-  //                  card_ptr; evicted ptr added to hot cache.
-  //                  No need to process res; immediately process card_ptr
-  //
-  // null     true    card not evicted from _card_counts; card_ptr added
-  //                  to hot cache.
-  //                  Nothing to do.
-  //
-  // non-null false   card evicted from _card_counts & replaced with
-  //                  card_ptr; evicted ptr is currently "cold" or
-  //                  caused an eviction from the hot cache.
-  //                  Immediately process res; process card_ptr.
-  //
-  // non-null true    card not evicted from _card_counts; card_ptr is
-  //                  currently cold, or caused an eviction from hot
-  //                  cache.
-  //                  Immediately process res; no need to process card_ptr.
-
-
-  jbyte* res = card_ptr;
-  bool defer = false;
-
-  // This gets set to true if the card being refined has references
-  // that point into the collection set.
-  bool oops_into_cset = false;
-
-  if (_cg1r->use_cache()) {
-    jbyte* res = _cg1r->cache_insert(card_ptr, &defer);
-    if (res != NULL && (res != card_ptr || defer)) {
-      start = _ct_bs->addr_for(res);
-      r = _g1->heap_region_containing(start);
-      if (r != NULL) {
-        // Checking whether the region we got back from the cache
-        // is young here is inappropriate. The region could have been
-        // freed, reallocated and tagged as young while in the cache.
-        // Hence we could see its young type change at any time.
-        //
-        // Process card pointer we get back from the hot card cache. This
-        // will check whether the region containing the card is young
-        // _after_ checking that the region has been allocated from.
-        oops_into_cset = concurrentRefineOneCard_impl(res, worker_i,
-                                                      false /* check_for_refs_into_cset */);
-        // The above call to concurrentRefineOneCard_impl is only
-        // performed if the hot card cache is enabled. This cache is
-        // disabled during an evacuation pause - which is the only
-        // time when we need know if the card contains references
-        // that point into the collection set. Also when the hot card
-        // cache is enabled, this code is executed by the concurrent
-        // refine threads - rather than the GC worker threads - and
-        // concurrentRefineOneCard_impl will return false.
-        assert(!oops_into_cset, "should not see true here");
-      }
-    }
-  }
-
-  if (!defer) {
-    oops_into_cset =
-      concurrentRefineOneCard_impl(card_ptr, worker_i, check_for_refs_into_cset);
-    // We should only be detecting that the card contains references
-    // that point into the collection set if the current thread is
-    // a GC worker thread.
-    assert(!oops_into_cset || SafepointSynchronize::is_at_safepoint(),
-           "invalid result at non safepoint");
-  }
-  return oops_into_cset;
+  return has_refs_into_cset;
 }
 
 class HRRSStatsIter: public HeapRegionClosure {
@@ -846,13 +797,16 @@
       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
       dcqs.concatenate_logs();
     }
-    bool cg1r_use_cache = _cg1r->use_cache();
-    _cg1r->set_use_cache(false);
+
+    G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
+    bool use_hot_card_cache = hot_card_cache->use_cache();
+    hot_card_cache->set_use_cache(false);
+
     DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
     updateRS(&into_cset_dcq, 0);
     _g1->into_cset_dirty_card_queue_set().clear();
-    _cg1r->set_use_cache(cg1r_use_cache);
 
+    hot_card_cache->set_use_cache(use_hot_card_cache);
     assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
   }
 }
--- a/src/share/vm/gc_implementation/g1/g1RemSet.hpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/g1RemSet.hpp	Fri May 10 09:24:20 2013 +0200
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2013, 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
@@ -66,14 +66,6 @@
   // references into the collection set.
   OopsInHeapRegionClosure** _cset_rs_update_cl;
 
-  // The routine that performs the actual work of refining a dirty
-  // card.
-  // If check_for_refs_into_refs is true then a true result is returned
-  // if the card contains oops that have references into the current
-  // collection set.
-  bool concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
-                                    bool check_for_refs_into_cset);
-
 public:
   // This is called to reset dual hash tables after the gc pause
   // is finished and the initial hash table is no longer being
@@ -90,8 +82,7 @@
   // function can be helpful in partitioning the work to be done. It
   // should be the same as the "i" passed to the calling thread's
   // work(i) function. In the sequential case this param will be ingored.
-  void oops_into_collection_set_do(OopsInHeapRegionClosure* blk,
-                                   int worker_i);
+  void oops_into_collection_set_do(OopsInHeapRegionClosure* blk, int worker_i);
 
   // Prepare for and cleanup after an oops_into_collection_set_do
   // call.  Must call each of these once before and after (in sequential
@@ -124,14 +115,13 @@
   void scrub_par(BitMap* region_bm, BitMap* card_bm,
                  uint worker_num, int claim_val);
 
-  // Refine the card corresponding to "card_ptr".  If "sts" is non-NULL,
-  // join and leave around parts that must be atomic wrt GC.  (NULL means
-  // being done at a safepoint.)
+  // Refine the card corresponding to "card_ptr".
   // If check_for_refs_into_cset is true, a true result is returned
   // if the given card contains oops that have references into the
   // current collection set.
-  virtual bool concurrentRefineOneCard(jbyte* card_ptr, int worker_i,
-                                       bool check_for_refs_into_cset);
+  virtual bool refine_card(jbyte* card_ptr,
+                           int worker_i,
+                           bool check_for_refs_into_cset);
 
   // Print any relevant summary info.
   virtual void print_summary_info();
--- a/src/share/vm/gc_implementation/g1/g1_globals.hpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/g1_globals.hpp	Fri May 10 09:24:20 2013 +0200
@@ -163,16 +163,12 @@
           "Select green, yellow and red zones adaptively to meet the "      \
           "the pause requirements.")                                        \
                                                                             \
-  develop(intx, G1ConcRSLogCacheSize, 10,                                   \
+  product(uintx, G1ConcRSLogCacheSize, 10,                                  \
           "Log base 2 of the length of conc RS hot-card cache.")            \
                                                                             \
-  develop(intx, G1ConcRSHotCardLimit, 4,                                    \
+  product(uintx, G1ConcRSHotCardLimit, 4,                                   \
           "The threshold that defines (>=) a hot card.")                    \
                                                                             \
-  develop(intx, G1MaxHotCardCountSizePercent, 25,                           \
-          "The maximum size of the hot card count cache as a "              \
-          "percentage of the number of cards for the maximum heap.")        \
-                                                                            \
   develop(bool, G1PrintOopAppls, false,                                     \
           "When true, print applications of closures to external locs.")    \
                                                                             \
@@ -247,10 +243,6 @@
           "If non-0 is the number of parallel rem set update threads, "     \
           "otherwise the value is determined ergonomically.")               \
                                                                             \
-  develop(intx, G1CardCountCacheExpandThreshold, 16,                        \
-          "Expand the card count cache if the number of collisions for "    \
-          "a particular entry exceeds this value.")                         \
-                                                                            \
   develop(bool, G1VerifyCTCleanup, false,                                   \
           "Verify card table cleanup.")                                     \
                                                                             \
--- a/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/heapRegionSeq.cpp	Fri May 10 09:24:20 2013 +0200
@@ -124,11 +124,11 @@
       }
       assert(_regions[index] == NULL, "invariant");
       _regions[index] = new_hr;
-      increment_length(&_allocated_length);
+      increment_allocated_length();
     }
     // Have to increment the length first, otherwise we will get an
     // assert failure at(index) below.
-    increment_length(&_length);
+    increment_length();
     HeapRegion* hr = at(index);
     list->add_as_tail(hr);
 
@@ -201,45 +201,29 @@
   }
 }
 
-MemRegion HeapRegionSeq::shrink_by(size_t shrink_bytes,
-                                   uint* num_regions_deleted) {
+uint HeapRegionSeq::shrink_by(uint num_regions_to_remove) {
   // Reset this in case it's currently pointing into the regions that
   // we just removed.
   _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");
+  assert(num_regions_to_remove < length(), "We should never remove all regions");
 
-  // around the loop, i will be the next region to be removed
-  uint 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;
-  *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;
+  uint i = 0;
+  for (; i < num_regions_to_remove; i++) {
+    HeapRegion* cur = at(length() - 1);
 
-    i -= 1;
-    *num_regions_deleted += 1;
-    shrink_bytes -= cur->capacity();
-    last_start = cur->bottom();
-    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");
+    if (!cur->is_empty()) {
+      // We have to give up if the region can not be moved
+      break;
   }
-  return MemRegion(last_start, end);
+    assert(!cur->isHumongous(), "Humongous regions should not be empty");
+
+    decrement_length();
+  }
+  return i;
 }
 
 #ifndef PRODUCT
--- a/src/share/vm/gc_implementation/g1/heapRegionSeq.hpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/gc_implementation/g1/heapRegionSeq.hpp	Fri May 10 09:24:20 2013 +0200
@@ -92,14 +92,19 @@
   // address is valid.
   inline uintx addr_to_index_biased(HeapWord* addr) const;
 
-  void increment_length(uint* length) {
-    assert(*length < _max_length, "pre-condition");
-    *length += 1;
+  void increment_allocated_length() {
+    assert(_allocated_length < _max_length, "pre-condition");
+    _allocated_length++;
   }
 
-  void decrement_length(uint* length) {
-    assert(*length > 0, "pre-condition");
-    *length -= 1;
+  void increment_length() {
+    assert(_length < _max_length, "pre-condition");
+    _length++;
+  }
+
+  void decrement_length() {
+    assert(_length > 0, "pre-condition");
+    _length--;
   }
 
  public:
@@ -153,11 +158,9 @@
   void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
 
   // 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, uint* num_regions_deleted);
+  // possible, up to num_regions_to_remove, from the suffix of the committed
+  // sequence. Return the actual number of removed regions.
+  uint shrink_by(uint num_regions_to_remove);
 
   // Do some sanity checking.
   void verify_optional() PRODUCT_RETURN;
--- a/src/share/vm/memory/collectorPolicy.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/memory/collectorPolicy.cpp	Fri May 10 09:24:20 2013 +0200
@@ -48,6 +48,17 @@
 // CollectorPolicy methods.
 
 void CollectorPolicy::initialize_flags() {
+  assert(max_alignment() >= min_alignment(),
+      err_msg("max_alignment: " SIZE_FORMAT " less than min_alignment: " SIZE_FORMAT,
+          max_alignment(), min_alignment()));
+  assert(max_alignment() % min_alignment() == 0,
+      err_msg("max_alignment: " SIZE_FORMAT " not aligned by min_alignment: " SIZE_FORMAT,
+          max_alignment(), min_alignment()));
+
+  if (MaxHeapSize < InitialHeapSize) {
+    vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
+  }
+
   if (MetaspaceSize > MaxMetaspaceSize) {
     MaxMetaspaceSize = MetaspaceSize;
   }
@@ -71,21 +82,9 @@
 }
 
 void CollectorPolicy::initialize_size_info() {
-  // User inputs from -mx and ms are aligned
-  set_initial_heap_byte_size(InitialHeapSize);
-  if (initial_heap_byte_size() == 0) {
-    set_initial_heap_byte_size(NewSize + OldSize);
-  }
-  set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
-                                           min_alignment()));
-
-  set_min_heap_byte_size(Arguments::min_heap_size());
-  if (min_heap_byte_size() == 0) {
-    set_min_heap_byte_size(NewSize + OldSize);
-  }
-  set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
-                                       min_alignment()));
-
+  // User inputs from -mx and ms must be aligned
+  set_min_heap_byte_size(align_size_up(Arguments::min_heap_size(), min_alignment()));
+  set_initial_heap_byte_size(align_size_up(InitialHeapSize, min_alignment()));
   set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
 
   // Check heap parameter properties
@@ -201,9 +200,6 @@
   // All sizes must be multiples of the generation granularity.
   set_min_alignment((uintx) Generation::GenGrain);
   set_max_alignment(compute_max_alignment());
-  assert(max_alignment() >= min_alignment() &&
-         max_alignment() % min_alignment() == 0,
-         "invalid alignment constraints");
 
   CollectorPolicy::initialize_flags();
 
@@ -233,9 +229,6 @@
   GenCollectorPolicy::initialize_flags();
 
   OldSize = align_size_down(OldSize, min_alignment());
-  if (NewSize + OldSize > MaxHeapSize) {
-    MaxHeapSize = NewSize + OldSize;
-  }
 
   if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
     // NewRatio will be used later to set the young generation size so we use
@@ -250,6 +243,27 @@
   }
   MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
 
+  // adjust max heap size if necessary
+  if (NewSize + OldSize > MaxHeapSize) {
+    if (FLAG_IS_CMDLINE(MaxHeapSize)) {
+      // somebody set a maximum heap size with the intention that we should not
+      // exceed it. Adjust New/OldSize as necessary.
+      uintx calculated_size = NewSize + OldSize;
+      double shrink_factor = (double) MaxHeapSize / calculated_size;
+      // align
+      NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
+      // OldSize is already aligned because above we aligned MaxHeapSize to
+      // max_alignment(), and we just made sure that NewSize is aligned to
+      // min_alignment(). In initialize_flags() we verified that max_alignment()
+      // is a multiple of min_alignment().
+      OldSize = MaxHeapSize - NewSize;
+    } else {
+      MaxHeapSize = NewSize + OldSize;
+    }
+  }
+  // need to do this again
+  MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
+
   always_do_update_barrier = UseConcMarkSweepGC;
 
   // Check validity of heap flags
--- a/src/share/vm/prims/whitebox.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/prims/whitebox.cpp	Fri May 10 09:24:20 2013 +0200
@@ -93,6 +93,15 @@
   return closure.found();
 WB_END
 
+WB_ENTRY(void, WB_PrintHeapSizes(JNIEnv* env, jobject o)) {
+  CollectorPolicy * p = Universe::heap()->collector_policy();
+  gclog_or_tty->print_cr("Minimum heap "SIZE_FORMAT" Initial heap "
+    SIZE_FORMAT" Maximum heap "SIZE_FORMAT" Min alignment "SIZE_FORMAT" Max alignment "SIZE_FORMAT,
+    p->min_heap_byte_size(), p->initial_heap_byte_size(), p->max_heap_byte_size(),
+    p->min_alignment(), p->max_alignment());
+}
+WB_END
+
 #if INCLUDE_ALL_GCS
 WB_ENTRY(jboolean, WB_G1IsHumongous(JNIEnv* env, jobject o, jobject obj))
   G1CollectedHeap* g1 = G1CollectedHeap::heap();
@@ -386,6 +395,7 @@
       CC"(Ljava/lang/String;[Lsun/hotspot/parser/DiagnosticCommand;)[Ljava/lang/Object;",
       (void*) &WB_ParseCommandLine
   },
+  {CC"printHeapSizes",     CC"()V",                   (void*)&WB_PrintHeapSizes    },
 #if INCLUDE_ALL_GCS
   {CC"g1InConcurrentMark", CC"()Z",                   (void*)&WB_G1InConcurrentMark},
   {CC"g1IsHumongous",      CC"(Ljava/lang/Object;)Z", (void*)&WB_G1IsHumongous     },
--- a/src/share/vm/runtime/arguments.cpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/runtime/arguments.cpp	Fri May 10 09:24:20 2013 +0200
@@ -747,16 +747,16 @@
     return;
   }
 
-  int index = *count;
+  int new_count = *count + 1;
 
   // expand the array and add arg to the last element
-  (*count)++;
   if (*bldarray == NULL) {
-    *bldarray = NEW_C_HEAP_ARRAY(char*, *count, mtInternal);
+    *bldarray = NEW_C_HEAP_ARRAY(char*, new_count, mtInternal);
   } else {
-    *bldarray = REALLOC_C_HEAP_ARRAY(char*, *bldarray, *count, mtInternal);
+    *bldarray = REALLOC_C_HEAP_ARRAY(char*, *bldarray, new_count, mtInternal);
   }
-  (*bldarray)[index] = strdup(arg);
+  (*bldarray)[*count] = strdup(arg);
+  *count = new_count;
 }
 
 void Arguments::build_jvm_args(const char* arg) {
@@ -1617,30 +1617,38 @@
     FLAG_SET_ERGO(uintx, MaxHeapSize, (uintx)reasonable_max);
   }
 
-  // If the initial_heap_size has not been set with InitialHeapSize
-  // or -Xms, then set it as fraction of the size of physical memory,
-  // respecting the maximum and minimum sizes of the heap.
-  if (FLAG_IS_DEFAULT(InitialHeapSize)) {
+  // If the minimum or initial heap_size have not been set or requested to be set
+  // ergonomically, set them accordingly.
+  if (InitialHeapSize == 0 || min_heap_size() == 0) {
     julong reasonable_minimum = (julong)(OldSize + NewSize);
 
     reasonable_minimum = MIN2(reasonable_minimum, (julong)MaxHeapSize);
 
     reasonable_minimum = limit_by_allocatable_memory(reasonable_minimum);
 
-    julong reasonable_initial = phys_mem / InitialRAMFraction;
-
-    reasonable_initial = MAX2(reasonable_initial, reasonable_minimum);
-    reasonable_initial = MIN2(reasonable_initial, (julong)MaxHeapSize);
-
-    reasonable_initial = limit_by_allocatable_memory(reasonable_initial);
-
-    if (PrintGCDetails && Verbose) {
-      // Cannot use gclog_or_tty yet.
-      tty->print_cr("  Initial heap size " SIZE_FORMAT, (uintx)reasonable_initial);
-      tty->print_cr("  Minimum heap size " SIZE_FORMAT, (uintx)reasonable_minimum);
+    if (InitialHeapSize == 0) {
+      julong reasonable_initial = phys_mem / InitialRAMFraction;
+
+      reasonable_initial = MAX3(reasonable_initial, reasonable_minimum, (julong)min_heap_size());
+      reasonable_initial = MIN2(reasonable_initial, (julong)MaxHeapSize);
+
+      reasonable_initial = limit_by_allocatable_memory(reasonable_initial);
+
+      if (PrintGCDetails && Verbose) {
+        // Cannot use gclog_or_tty yet.
+        tty->print_cr("  Initial heap size " SIZE_FORMAT, (uintx)reasonable_initial);
+      }
+      FLAG_SET_ERGO(uintx, InitialHeapSize, (uintx)reasonable_initial);
     }
-    FLAG_SET_ERGO(uintx, InitialHeapSize, (uintx)reasonable_initial);
-    set_min_heap_size((uintx)reasonable_minimum);
+    // If the minimum heap size has not been set (via -Xms),
+    // synchronize with InitialHeapSize to avoid errors with the default value.
+    if (min_heap_size() == 0) {
+      set_min_heap_size(MIN2((uintx)reasonable_minimum, InitialHeapSize));
+      if (PrintGCDetails && Verbose) {
+        // Cannot use gclog_or_tty yet.
+        tty->print_cr("  Minimum heap size " SIZE_FORMAT, min_heap_size());
+      }
+    }
   }
 }
 
@@ -2043,6 +2051,10 @@
                                         "G1RefProcDrainInterval");
     status = status && verify_min_value((intx)G1ConcMarkStepDurationMillis, 1,
                                         "G1ConcMarkStepDurationMillis");
+    status = status && verify_interval(G1ConcRSHotCardLimit, 0, max_jubyte,
+                                       "G1ConcRSHotCardLimit");
+    status = status && verify_interval(G1ConcRSLogCacheSize, 0, 31,
+                                       "G1ConcRSLogCacheSize");
   }
 #endif // INCLUDE_ALL_GCS
 
@@ -2426,7 +2438,8 @@
     // -Xms
     } else if (match_option(option, "-Xms", &tail)) {
       julong long_initial_heap_size = 0;
-      ArgsRange errcode = parse_memory_size(tail, &long_initial_heap_size, 1);
+      // an initial heap size of 0 means automatically determine
+      ArgsRange errcode = parse_memory_size(tail, &long_initial_heap_size, 0);
       if (errcode != arg_in_range) {
         jio_fprintf(defaultStream::error_stream(),
                     "Invalid initial heap size: %s\n", option->optionString);
@@ -2437,7 +2450,7 @@
       // Currently the minimum size and the initial heap sizes are the same.
       set_min_heap_size(InitialHeapSize);
     // -Xmx
-    } else if (match_option(option, "-Xmx", &tail)) {
+    } else if (match_option(option, "-Xmx", &tail) || match_option(option, "-XX:MaxHeapSize=", &tail)) {
       julong long_max_heap_size = 0;
       ArgsRange errcode = parse_memory_size(tail, &long_max_heap_size, 1);
       if (errcode != arg_in_range) {
--- a/src/share/vm/runtime/globals.hpp	Thu May 09 16:27:51 2013 -0400
+++ b/src/share/vm/runtime/globals.hpp	Fri May 10 09:24:20 2013 +0200
@@ -2968,7 +2968,7 @@
                                                                             \
   /* gc parameters */                                                       \
   product(uintx, InitialHeapSize, 0,                                        \
-          "Initial heap size (in bytes); zero means OldSize + NewSize")     \
+          "Initial heap size (in bytes); zero means use ergonomics")        \
                                                                             \
   product(uintx, MaxHeapSize, ScaleForWordSize(96*M),                       \
           "Maximum heap size (in bytes)")                                   \
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/gc/concurrentMarkSweep/CheckAllocateAndSystemGC.java	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test CheckAllocateAndSystemGC
+ * @summary CMS: assert(used() == used_after_gc && used_after_gc <= capacity()) failed: used: 0 used_after_gc: 292080 capacity: 1431699456
+ * @bug 8013032
+ * @key gc
+ * @key regression
+ * @library /testlibrary
+ * @run main/othervm CheckAllocateAndSystemGC
+ * @author jon.masamitsu@oracle.com
+ */
+
+import com.oracle.java.testlibrary.*;
+
+public class CheckAllocateAndSystemGC {
+  public static void main(String args[]) throws Exception {
+
+    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
+      "-showversion",
+      "-XX:+UseConcMarkSweepGC",
+      "-Xmn4m",
+      "-XX:MaxTenuringThreshold=1",
+      "-XX:-UseCMSCompactAtFullCollection",
+      "CheckAllocateAndSystemGC$AllocateAndSystemGC"
+      );
+
+    OutputAnalyzer output = new OutputAnalyzer(pb.start());
+
+    output.shouldNotContain("error");
+
+    output.shouldHaveExitValue(0);
+  }
+  static class AllocateAndSystemGC {
+    public static void main(String [] args) {
+      Integer x[] = new Integer [1000];
+      // Allocate enough objects to cause a minor collection.
+      // These allocations suffice for a 4m young geneneration.
+      for (int i = 0; i < 100; i++) {
+        Integer y[] = new Integer[10000];
+      }
+      System.gc();
+    }
+  }
+}
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/gc/concurrentMarkSweep/SystemGCOnForegroundCollector.java	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test SystemGCOnForegroundCollector
+ * @summary CMS: Call reset_after_compaction() only if a compaction has been done
+ * @bug 8013184
+ * @key gc
+ * @key regression
+ * @library /testlibrary
+ * @run main/othervm SystemGCOnForegroundCollector
+ * @author jon.masamitsu@oracle.com
+ */
+
+import com.oracle.java.testlibrary.*;
+
+public class SystemGCOnForegroundCollector {
+  public static void main(String args[]) throws Exception {
+
+    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
+      "-showversion",
+      "-XX:+UseConcMarkSweepGC",
+      "-XX:MaxTenuringThreshold=1",
+      "-XX:-UseCMSCompactAtFullCollection",
+      ThreePlusMSSystemGC.class.getName()
+      );
+
+    OutputAnalyzer output = new OutputAnalyzer(pb.start());
+
+    output.shouldNotContain("error");
+
+    output.shouldHaveExitValue(0);
+  }
+
+  static class ThreePlusMSSystemGC {
+    public static void main(String [] args) {
+      // From running this test 3 System.gc() were always
+      // enough to see the failure but the cause of the failure
+      // depends on how objects are allocated in the CMS generation
+      // which is non-deterministic.  Use 30 iterations for a more
+      // reliable test.
+      for (int i = 0; i < 30; i++) {
+        System.gc();
+      }
+    }
+  }
+}
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/gc/g1/TestRegionAlignment.java	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test TestRegionAlignment.java
+ * @bug 8013791
+ * @summary Make sure that G1 ergonomics pick a heap size that is aligned with the region size
+ * @run main/othervm -XX:+UseG1GC -XX:G1HeapRegionSize=32m -XX:MaxRAM=555m TestRegionAlignment
+ *
+ * When G1 ergonomically picks a maximum heap size it must be aligned to the region size.
+ * This test tries to get the VM to pick a small and unaligned heap size (by using MaxRAM=555) and a
+ * large region size (by using -XX:G1HeapRegionSize=32m). This will fail without the fix for 8013791.
+ */
+public class TestRegionAlignment {
+    public static void main(String[] args) { }
+}
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/gc/g1/TestShrinkToOneRegion.java	Fri May 10 09:24:20 2013 +0200
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2013, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test TestShrinkToOneRegion.java
+ * @bug 8013872
+ * @summary Shrinking the heap down to one region used to hit an assert
+ * @run main/othervm -XX:+UseG1GC -XX:G1HeapRegionSize=32m -Xmx256m TestShrinkToOneRegion
+ *
+ * Doing a System.gc() without having allocated many objects will shrink the heap.
+ * With a large region size we will shrink the heap to one region.
+ */
+public class TestShrinkToOneRegion {
+    public static void main(String[] args) {
+        System.gc();
+    }
+}
--- a/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java	Thu May 09 16:27:51 2013 -0400
+++ b/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java	Fri May 10 09:24:20 2013 +0200
@@ -61,6 +61,9 @@
     registerNatives();
   }
 
+  // Arguments
+  public native void printHeapSizes();
+
   // Memory
   public native long getObjectAddress(Object o);
   public native int  getHeapOopSize();