--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Mon Jul 21 09:59:54 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Mon Jul 21 10:00:31 2014 +0200
@@ -2950,10 +2950,17 @@
   }
 }
 
-CompactibleSpace* G1CollectedHeap::first_compactible_space() {
-  return n_regions() > 0 ? region_at(0) : NULL;
-}
-
+HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
+  // We're not using an iterator given that it will wrap around when
+  // it reaches the last region and this is not what we want here.
+  for (uint index = from->hrs_index() + 1; index < n_regions(); index++) {
+    HeapRegion* hr = region_at(index);
+    if (!hr->isHumongous()) {
+      return hr;
+    }
+  }
+  return NULL;
+}
 
 Space* G1CollectedHeap::space_containing(const void* addr) const {
   return heap_region_containing(addr);

--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Mon Jul 21 09:59:54 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Mon Jul 21 10:00:31 2014 +0200
@@ -1158,19 +1158,19 @@
   }
 
   // The total number of regions in the heap.
-  uint n_regions() { return _hrs.length(); }
+  uint n_regions() const { return _hrs.length(); }
 
   // The max number of regions in the heap.
-  uint max_regions() { return _hrs.max_length(); }
+  uint max_regions() const { return _hrs.max_length(); }
 
   // The number of regions that are completely free.
-  uint free_regions() { return _free_list.length(); }
+  uint free_regions() const { return _free_list.length(); }
 
   // The number of regions that are not completely free.
-  uint used_regions() { return n_regions() - free_regions(); }
+  uint used_regions() const { return n_regions() - free_regions(); }
 
   // The number of regions available for "regular" expansion.
-  uint expansion_regions() { return _expansion_regions; }
+  uint expansion_regions() const { return _expansion_regions; }
 
   // Factory method for HeapRegion instances. It will return NULL if
   // the allocation fails.
@@ -1392,8 +1392,7 @@
   // As above but starting from region r
   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
 
-  // Returns the first (lowest address) compactible space in the heap.
-  virtual CompactibleSpace* first_compactible_space();
+  HeapRegion* next_compaction_region(const HeapRegion* from) const;
 
   // A CollectedHeap will contain some number of spaces.  This finds the
   // space containing a given address, or else returns NULL.

--- a/hotspot/src/share/vm/gc_implementation/g1/g1MarkSweep.cpp	Mon Jul 21 09:59:54 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1MarkSweep.cpp	Mon Jul 21 10:00:31 2014 +0200
@@ -201,6 +201,23 @@
   CompactPoint _cp;
   HeapRegionSetCount _humongous_regions_removed;
 
+  bool is_cp_initialized() const {
+    return _cp.space != NULL;
+  }
+
+  void prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
+    // If this is the first live region that we came across which we can compact,
+    // initialize the CompactPoint.
+    if (!is_cp_initialized()) {
+      _cp.space = hr;
+      _cp.threshold = hr->initialize_threshold();
+    }
+    hr->prepare_for_compaction(&_cp);
+    // Also clear the part of the card table that will be unused after
+    // compaction.
+    _mrbs->clear(MemRegion(hr->compaction_top(), end));
+  }
+
   void free_humongous_region(HeapRegion* hr) {
     HeapWord* end = hr->end();
     FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
@@ -212,18 +229,15 @@
     _humongous_regions_removed.increment(1u, hr->capacity());
 
     _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
-    hr->prepare_for_compaction(&_cp);
-    // Also clear the part of the card table that will be unused after
-    // compaction.
-    _mrbs->clear(MemRegion(hr->compaction_top(), end));
+    prepare_for_compaction(hr, end);
     dummy_free_list.remove_all();
   }
 
 public:
-  G1PrepareCompactClosure(CompactibleSpace* cs)
+  G1PrepareCompactClosure()
   : _g1h(G1CollectedHeap::heap()),
     _mrbs(_g1h->g1_barrier_set()),
-    _cp(NULL, cs, cs->initialize_threshold()),
+    _cp(NULL),
     _humongous_regions_removed() { }
 
   void update_sets() {
@@ -246,10 +260,7 @@
         assert(hr->continuesHumongous(), "Invalid humongous.");
       }
     } else {
-      hr->prepare_for_compaction(&_cp);
-      // Also clear the part of the card table that will be unused after
-      // compaction.
-      _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
+      prepare_for_compaction(hr, hr->end());
     }
     return false;
   }
@@ -267,14 +278,7 @@
   GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
   GenMarkSweep::trace("2");
 
-  // find the first region
-  HeapRegion* r = g1h->region_at(0);
-  CompactibleSpace* sp = r;
-  if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
-    sp = r->next_compaction_space();
-  }
-
-  G1PrepareCompactClosure blk(sp);
+  G1PrepareCompactClosure blk;
   g1h->heap_region_iterate(&blk);
   blk.update_sets();
 }

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Mon Jul 21 09:59:54 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp	Mon Jul 21 10:00:31 2014 +0200
@@ -381,18 +381,7 @@
 }
 
 CompactibleSpace* HeapRegion::next_compaction_space() const {
-  // We're not using an iterator given that it will wrap around when
-  // it reaches the last region and this is not what we want here.
-  G1CollectedHeap* g1h = G1CollectedHeap::heap();
-  uint index = hrs_index() + 1;
-  while (index < g1h->n_regions()) {
-    HeapRegion* hr = g1h->region_at(index);
-    if (!hr->isHumongous()) {
-      return hr;
-    }
-    index += 1;
-  }
-  return NULL;
+  return G1CollectedHeap::heap()->next_compaction_region(this);
 }
 
 void HeapRegion::note_self_forwarding_removal_start(bool during_initial_mark,

--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.hpp	Mon Jul 21 09:59:54 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionSet.hpp	Mon Jul 21 10:00:31 2014 +0200
@@ -119,7 +119,7 @@
 public:
   const char* name() { return _name; }
 
-  uint length() { return _count.length(); }
+  uint length() const { return _count.length(); }
 
   bool is_empty() { return _count.length() == 0; }
 

--- a/hotspot/src/share/vm/memory/genCollectedHeap.cpp	Mon Jul 21 09:59:54 2014 +0200
+++ b/hotspot/src/share/vm/memory/genCollectedHeap.cpp	Mon Jul 21 10:00:31 2014 +0200
@@ -1088,7 +1088,7 @@
   guarantee(_n_gens = 2, "Wrong number of generations");
   Generation* old_gen = _gens[1];
   // Start by compacting into same gen.
-  CompactPoint cp(old_gen, NULL, NULL);
+  CompactPoint cp(old_gen);
   old_gen->prepare_for_compaction(&cp);
   Generation* young_gen = _gens[0];
   young_gen->prepare_for_compaction(&cp);

--- a/hotspot/src/share/vm/memory/space.hpp	Mon Jul 21 09:59:54 2014 +0200
+++ b/hotspot/src/share/vm/memory/space.hpp	Mon Jul 21 10:00:31 2014 +0200
@@ -330,9 +330,9 @@
   Generation* gen;
   CompactibleSpace* space;
   HeapWord* threshold;
-  CompactPoint(Generation* _gen, CompactibleSpace* _space,
-               HeapWord* _threshold) :
-    gen(_gen), space(_space), threshold(_threshold) {}
+
+  CompactPoint(Generation* _gen) :
+    gen(_gen), space(NULL), threshold(0) {}
 };