src/hotspot/share/gc/g1/heapRegion.cpp
changeset 47216 71c04702a3d5
parent 46968 9119841280f4
child 47885 5caa1d5f74c1
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/heapRegion.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,910 @@
+/*
+ * Copyright (c) 2001, 2017, 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 "code/nmethod.hpp"
+#include "gc/g1/g1BlockOffsetTable.inline.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
+#include "gc/g1/g1HeapRegionTraceType.hpp"
+#include "gc/g1/g1OopClosures.inline.hpp"
+#include "gc/g1/heapRegion.inline.hpp"
+#include "gc/g1/heapRegionBounds.inline.hpp"
+#include "gc/g1/heapRegionManager.inline.hpp"
+#include "gc/g1/heapRegionRemSet.hpp"
+#include "gc/g1/heapRegionTracer.hpp"
+#include "gc/shared/genOopClosures.inline.hpp"
+#include "gc/shared/space.inline.hpp"
+#include "logging/log.hpp"
+#include "logging/logStream.hpp"
+#include "memory/iterator.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/orderAccess.inline.hpp"
+
+int    HeapRegion::LogOfHRGrainBytes = 0;
+int    HeapRegion::LogOfHRGrainWords = 0;
+size_t HeapRegion::GrainBytes        = 0;
+size_t HeapRegion::GrainWords        = 0;
+size_t HeapRegion::CardsPerRegion    = 0;
+
+size_t HeapRegion::max_region_size() {
+  return HeapRegionBounds::max_size();
+}
+
+size_t HeapRegion::min_region_size_in_words() {
+  return HeapRegionBounds::min_size() >> LogHeapWordSize;
+}
+
+void HeapRegion::setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size) {
+  size_t region_size = G1HeapRegionSize;
+  if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
+    size_t average_heap_size = (initial_heap_size + max_heap_size) / 2;
+    region_size = MAX2(average_heap_size / HeapRegionBounds::target_number(),
+                       HeapRegionBounds::min_size());
+  }
+
+  int region_size_log = log2_long((jlong) region_size);
+  // Recalculate the region size to make sure it's a power of
+  // 2. This means that region_size is the largest power of 2 that's
+  // <= what we've calculated so far.
+  region_size = ((size_t)1 << region_size_log);
+
+  // Now make sure that we don't go over or under our limits.
+  if (region_size < HeapRegionBounds::min_size()) {
+    region_size = HeapRegionBounds::min_size();
+  } else if (region_size > HeapRegionBounds::max_size()) {
+    region_size = HeapRegionBounds::max_size();
+  }
+
+  // And recalculate the log.
+  region_size_log = log2_long((jlong) region_size);
+
+  // Now, set up the globals.
+  guarantee(LogOfHRGrainBytes == 0, "we should only set it once");
+  LogOfHRGrainBytes = region_size_log;
+
+  guarantee(LogOfHRGrainWords == 0, "we should only set it once");
+  LogOfHRGrainWords = LogOfHRGrainBytes - LogHeapWordSize;
+
+  guarantee(GrainBytes == 0, "we should only set it once");
+  // The cast to int is safe, given that we've bounded region_size by
+  // MIN_REGION_SIZE and MAX_REGION_SIZE.
+  GrainBytes = region_size;
+  log_info(gc, heap)("Heap region size: " SIZE_FORMAT "M", GrainBytes / M);
+
+  guarantee(GrainWords == 0, "we should only set it once");
+  GrainWords = GrainBytes >> LogHeapWordSize;
+  guarantee((size_t) 1 << LogOfHRGrainWords == GrainWords, "sanity");
+
+  guarantee(CardsPerRegion == 0, "we should only set it once");
+  CardsPerRegion = GrainBytes >> CardTableModRefBS::card_shift;
+
+  if (G1HeapRegionSize != GrainBytes) {
+    FLAG_SET_ERGO(size_t, G1HeapRegionSize, GrainBytes);
+  }
+}
+
+void HeapRegion::reset_after_compaction() {
+  G1ContiguousSpace::reset_after_compaction();
+  // After a compaction the mark bitmap is invalid, so we must
+  // treat all objects as being inside the unmarked area.
+  zero_marked_bytes();
+  init_top_at_mark_start();
+}
+
+void HeapRegion::hr_clear(bool keep_remset, bool clear_space, bool locked) {
+  assert(_humongous_start_region == NULL,
+         "we should have already filtered out humongous regions");
+  assert(!in_collection_set(),
+         "Should not clear heap region %u in the collection set", hrm_index());
+
+  set_allocation_context(AllocationContext::system());
+  set_young_index_in_cset(-1);
+  uninstall_surv_rate_group();
+  set_free();
+  reset_pre_dummy_top();
+
+  if (!keep_remset) {
+    if (locked) {
+      rem_set()->clear_locked();
+    } else {
+      rem_set()->clear();
+    }
+  }
+
+  zero_marked_bytes();
+
+  init_top_at_mark_start();
+  _gc_time_stamp = G1CollectedHeap::heap()->get_gc_time_stamp();
+  if (clear_space) clear(SpaceDecorator::Mangle);
+}
+
+void HeapRegion::par_clear() {
+  assert(used() == 0, "the region should have been already cleared");
+  assert(capacity() == HeapRegion::GrainBytes, "should be back to normal");
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->clear();
+  CardTableModRefBS* ct_bs =
+    barrier_set_cast<CardTableModRefBS>(G1CollectedHeap::heap()->barrier_set());
+  ct_bs->clear(MemRegion(bottom(), end()));
+}
+
+void HeapRegion::calc_gc_efficiency() {
+  // GC efficiency is the ratio of how much space would be
+  // reclaimed over how long we predict it would take to reclaim it.
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
+  G1Policy* g1p = g1h->g1_policy();
+
+  // Retrieve a prediction of the elapsed time for this region for
+  // a mixed gc because the region will only be evacuated during a
+  // mixed gc.
+  double region_elapsed_time_ms =
+    g1p->predict_region_elapsed_time_ms(this, false /* for_young_gc */);
+  _gc_efficiency = (double) reclaimable_bytes() / region_elapsed_time_ms;
+}
+
+void HeapRegion::set_free() {
+  report_region_type_change(G1HeapRegionTraceType::Free);
+  _type.set_free();
+}
+
+void HeapRegion::set_eden() {
+  report_region_type_change(G1HeapRegionTraceType::Eden);
+  _type.set_eden();
+}
+
+void HeapRegion::set_eden_pre_gc() {
+  report_region_type_change(G1HeapRegionTraceType::Eden);
+  _type.set_eden_pre_gc();
+}
+
+void HeapRegion::set_survivor() {
+  report_region_type_change(G1HeapRegionTraceType::Survivor);
+  _type.set_survivor();
+}
+
+void HeapRegion::move_to_old() {
+  if (_type.relabel_as_old()) {
+    report_region_type_change(G1HeapRegionTraceType::Old);
+  }
+}
+
+void HeapRegion::set_old() {
+  report_region_type_change(G1HeapRegionTraceType::Old);
+  _type.set_old();
+}
+
+void HeapRegion::set_open_archive() {
+  report_region_type_change(G1HeapRegionTraceType::OpenArchive);
+  _type.set_open_archive();
+}
+
+void HeapRegion::set_closed_archive() {
+  report_region_type_change(G1HeapRegionTraceType::ClosedArchive);
+  _type.set_closed_archive();
+}
+
+void HeapRegion::set_starts_humongous(HeapWord* obj_top, size_t fill_size) {
+  assert(!is_humongous(), "sanity / pre-condition");
+  assert(top() == bottom(), "should be empty");
+
+  report_region_type_change(G1HeapRegionTraceType::StartsHumongous);
+  _type.set_starts_humongous();
+  _humongous_start_region = this;
+
+  _bot_part.set_for_starts_humongous(obj_top, fill_size);
+}
+
+void HeapRegion::set_continues_humongous(HeapRegion* first_hr) {
+  assert(!is_humongous(), "sanity / pre-condition");
+  assert(top() == bottom(), "should be empty");
+  assert(first_hr->is_starts_humongous(), "pre-condition");
+
+  report_region_type_change(G1HeapRegionTraceType::ContinuesHumongous);
+  _type.set_continues_humongous();
+  _humongous_start_region = first_hr;
+
+  _bot_part.set_object_can_span(true);
+}
+
+void HeapRegion::clear_humongous() {
+  assert(is_humongous(), "pre-condition");
+
+  assert(capacity() == HeapRegion::GrainBytes, "pre-condition");
+  _humongous_start_region = NULL;
+
+  _bot_part.set_object_can_span(false);
+}
+
+HeapRegion::HeapRegion(uint hrm_index,
+                       G1BlockOffsetTable* bot,
+                       MemRegion mr) :
+    G1ContiguousSpace(bot),
+    _hrm_index(hrm_index),
+    _allocation_context(AllocationContext::system()),
+    _humongous_start_region(NULL),
+    _evacuation_failed(false),
+    _prev_marked_bytes(0), _next_marked_bytes(0), _gc_efficiency(0.0),
+    _next(NULL), _prev(NULL),
+#ifdef ASSERT
+    _containing_set(NULL),
+#endif // ASSERT
+     _young_index_in_cset(-1), _surv_rate_group(NULL), _age_index(-1),
+    _rem_set(NULL), _recorded_rs_length(0), _predicted_elapsed_time_ms(0)
+{
+  _rem_set = new HeapRegionRemSet(bot, this);
+
+  initialize(mr);
+}
+
+void HeapRegion::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
+  assert(_rem_set->is_empty(), "Remembered set must be empty");
+
+  G1ContiguousSpace::initialize(mr, clear_space, mangle_space);
+
+  hr_clear(false /*par*/, false /*clear_space*/);
+  set_top(bottom());
+  record_timestamp();
+}
+
+void HeapRegion::report_region_type_change(G1HeapRegionTraceType::Type to) {
+  HeapRegionTracer::send_region_type_change(_hrm_index,
+                                            get_trace_type(),
+                                            to,
+                                            (uintptr_t)bottom(),
+                                            used(),
+                                            (uint)allocation_context());
+}
+
+CompactibleSpace* HeapRegion::next_compaction_space() const {
+  return G1CollectedHeap::heap()->next_compaction_region(this);
+}
+
+void HeapRegion::note_self_forwarding_removal_start(bool during_initial_mark,
+                                                    bool during_conc_mark) {
+  // We always recreate the prev marking info and we'll explicitly
+  // mark all objects we find to be self-forwarded on the prev
+  // bitmap. So all objects need to be below PTAMS.
+  _prev_marked_bytes = 0;
+
+  if (during_initial_mark) {
+    // During initial-mark, we'll also explicitly mark all objects
+    // we find to be self-forwarded on the next bitmap. So all
+    // objects need to be below NTAMS.
+    _next_top_at_mark_start = top();
+    _next_marked_bytes = 0;
+  } else if (during_conc_mark) {
+    // During concurrent mark, all objects in the CSet (including
+    // the ones we find to be self-forwarded) are implicitly live.
+    // So all objects need to be above NTAMS.
+    _next_top_at_mark_start = bottom();
+    _next_marked_bytes = 0;
+  }
+}
+
+void HeapRegion::note_self_forwarding_removal_end(size_t marked_bytes) {
+  assert(marked_bytes <= used(),
+         "marked: " SIZE_FORMAT " used: " SIZE_FORMAT, marked_bytes, used());
+  _prev_top_at_mark_start = top();
+  _prev_marked_bytes = marked_bytes;
+}
+
+// Code roots support
+
+void HeapRegion::add_strong_code_root(nmethod* nm) {
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->add_strong_code_root(nm);
+}
+
+void HeapRegion::add_strong_code_root_locked(nmethod* nm) {
+  assert_locked_or_safepoint(CodeCache_lock);
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->add_strong_code_root_locked(nm);
+}
+
+void HeapRegion::remove_strong_code_root(nmethod* nm) {
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->remove_strong_code_root(nm);
+}
+
+void HeapRegion::strong_code_roots_do(CodeBlobClosure* blk) const {
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->strong_code_roots_do(blk);
+}
+
+class VerifyStrongCodeRootOopClosure: public OopClosure {
+  const HeapRegion* _hr;
+  bool _failures;
+  bool _has_oops_in_region;
+
+  template <class T> void do_oop_work(T* p) {
+    T heap_oop = oopDesc::load_heap_oop(p);
+    if (!oopDesc::is_null(heap_oop)) {
+      oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
+
+      // Note: not all the oops embedded in the nmethod are in the
+      // current region. We only look at those which are.
+      if (_hr->is_in(obj)) {
+        // Object is in the region. Check that its less than top
+        if (_hr->top() <= (HeapWord*)obj) {
+          // Object is above top
+          log_error(gc, verify)("Object " PTR_FORMAT " in region [" PTR_FORMAT ", " PTR_FORMAT ") is above top " PTR_FORMAT,
+                               p2i(obj), p2i(_hr->bottom()), p2i(_hr->end()), p2i(_hr->top()));
+          _failures = true;
+          return;
+        }
+        // Nmethod has at least one oop in the current region
+        _has_oops_in_region = true;
+      }
+    }
+  }
+
+public:
+  VerifyStrongCodeRootOopClosure(const HeapRegion* hr):
+    _hr(hr), _failures(false), _has_oops_in_region(false) {}
+
+  void do_oop(narrowOop* p) { do_oop_work(p); }
+  void do_oop(oop* p)       { do_oop_work(p); }
+
+  bool failures()           { return _failures; }
+  bool has_oops_in_region() { return _has_oops_in_region; }
+};
+
+class VerifyStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
+  const HeapRegion* _hr;
+  bool _failures;
+public:
+  VerifyStrongCodeRootCodeBlobClosure(const HeapRegion* hr) :
+    _hr(hr), _failures(false) {}
+
+  void do_code_blob(CodeBlob* cb) {
+    nmethod* nm = (cb == NULL) ? NULL : cb->as_compiled_method()->as_nmethod_or_null();
+    if (nm != NULL) {
+      // Verify that the nemthod is live
+      if (!nm->is_alive()) {
+        log_error(gc, verify)("region [" PTR_FORMAT "," PTR_FORMAT "] has dead nmethod " PTR_FORMAT " in its strong code roots",
+                              p2i(_hr->bottom()), p2i(_hr->end()), p2i(nm));
+        _failures = true;
+      } else {
+        VerifyStrongCodeRootOopClosure oop_cl(_hr);
+        nm->oops_do(&oop_cl);
+        if (!oop_cl.has_oops_in_region()) {
+          log_error(gc, verify)("region [" PTR_FORMAT "," PTR_FORMAT "] has nmethod " PTR_FORMAT " in its strong code roots with no pointers into region",
+                                p2i(_hr->bottom()), p2i(_hr->end()), p2i(nm));
+          _failures = true;
+        } else if (oop_cl.failures()) {
+          log_error(gc, verify)("region [" PTR_FORMAT "," PTR_FORMAT "] has other failures for nmethod " PTR_FORMAT,
+                                p2i(_hr->bottom()), p2i(_hr->end()), p2i(nm));
+          _failures = true;
+        }
+      }
+    }
+  }
+
+  bool failures()       { return _failures; }
+};
+
+void HeapRegion::verify_strong_code_roots(VerifyOption vo, bool* failures) const {
+  if (!G1VerifyHeapRegionCodeRoots) {
+    // We're not verifying code roots.
+    return;
+  }
+  if (vo == VerifyOption_G1UseMarkWord) {
+    // Marking verification during a full GC is performed after class
+    // unloading, code cache unloading, etc so the strong code roots
+    // attached to each heap region are in an inconsistent state. They won't
+    // be consistent until the strong code roots are rebuilt after the
+    // actual GC. Skip verifying the strong code roots in this particular
+    // time.
+    assert(VerifyDuringGC, "only way to get here");
+    return;
+  }
+
+  HeapRegionRemSet* hrrs = rem_set();
+  size_t strong_code_roots_length = hrrs->strong_code_roots_list_length();
+
+  // if this region is empty then there should be no entries
+  // on its strong code root list
+  if (is_empty()) {
+    if (strong_code_roots_length > 0) {
+      log_error(gc, verify)("region [" PTR_FORMAT "," PTR_FORMAT "] is empty but has " SIZE_FORMAT " code root entries",
+                            p2i(bottom()), p2i(end()), strong_code_roots_length);
+      *failures = true;
+    }
+    return;
+  }
+
+  if (is_continues_humongous()) {
+    if (strong_code_roots_length > 0) {
+      log_error(gc, verify)("region " HR_FORMAT " is a continuation of a humongous region but has " SIZE_FORMAT " code root entries",
+                            HR_FORMAT_PARAMS(this), strong_code_roots_length);
+      *failures = true;
+    }
+    return;
+  }
+
+  VerifyStrongCodeRootCodeBlobClosure cb_cl(this);
+  strong_code_roots_do(&cb_cl);
+
+  if (cb_cl.failures()) {
+    *failures = true;
+  }
+}
+
+void HeapRegion::print() const { print_on(tty); }
+void HeapRegion::print_on(outputStream* st) const {
+  st->print("|%4u", this->_hrm_index);
+  st->print("|" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT,
+            p2i(bottom()), p2i(top()), p2i(end()));
+  st->print("|%3d%%", (int) ((double) used() * 100 / capacity()));
+  st->print("|%2s", get_short_type_str());
+  if (in_collection_set()) {
+    st->print("|CS");
+  } else {
+    st->print("|  ");
+  }
+  st->print("|TS%3u", _gc_time_stamp);
+  st->print("|AC%3u", allocation_context());
+  st->print_cr("|TAMS " PTR_FORMAT ", " PTR_FORMAT "|",
+               p2i(prev_top_at_mark_start()), p2i(next_top_at_mark_start()));
+}
+
+class G1VerificationClosure : public OopClosure {
+protected:
+  G1CollectedHeap* _g1h;
+  CardTableModRefBS* _bs;
+  oop _containing_obj;
+  bool _failures;
+  int _n_failures;
+  VerifyOption _vo;
+public:
+  // _vo == UsePrevMarking -> use "prev" marking information,
+  // _vo == UseNextMarking -> use "next" marking information,
+  // _vo == UseMarkWord    -> use mark word from object header.
+  G1VerificationClosure(G1CollectedHeap* g1h, VerifyOption vo) :
+    _g1h(g1h), _bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
+    _containing_obj(NULL), _failures(false), _n_failures(0), _vo(vo) {
+  }
+
+  void set_containing_obj(oop obj) {
+    _containing_obj = obj;
+  }
+
+  bool failures() { return _failures; }
+  int n_failures() { return _n_failures; }
+
+  void print_object(outputStream* out, oop obj) {
+#ifdef PRODUCT
+    Klass* k = obj->klass();
+    const char* class_name = k->external_name();
+    out->print_cr("class name %s", class_name);
+#else // PRODUCT
+    obj->print_on(out);
+#endif // PRODUCT
+  }
+};
+
+class VerifyLiveClosure : public G1VerificationClosure {
+public:
+  VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) : G1VerificationClosure(g1h, vo) {}
+  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
+  virtual void do_oop(oop* p) { do_oop_work(p); }
+
+  template <class T>
+  void do_oop_work(T* p) {
+    assert(_containing_obj != NULL, "Precondition");
+    assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
+      "Precondition");
+    verify_liveness(p);
+  }
+
+  template <class T>
+  void verify_liveness(T* p) {
+    T heap_oop = oopDesc::load_heap_oop(p);
+    Log(gc, verify) log;
+    if (!oopDesc::is_null(heap_oop)) {
+      oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
+      bool failed = false;
+      if (!_g1h->is_in_closed_subset(obj) || _g1h->is_obj_dead_cond(obj, _vo)) {
+        MutexLockerEx x(ParGCRareEvent_lock,
+          Mutex::_no_safepoint_check_flag);
+
+        if (!_failures) {
+          log.error("----------");
+        }
+        ResourceMark rm;
+        if (!_g1h->is_in_closed_subset(obj)) {
+          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
+          log.error("Field " PTR_FORMAT " of live obj " PTR_FORMAT " in region [" PTR_FORMAT ", " PTR_FORMAT ")",
+            p2i(p), p2i(_containing_obj), p2i(from->bottom()), p2i(from->end()));
+          LogStream ls(log.error());
+          print_object(&ls, _containing_obj);
+          log.error("points to obj " PTR_FORMAT " not in the heap", p2i(obj));
+        } else {
+          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
+          HeapRegion* to = _g1h->heap_region_containing((HeapWord*)obj);
+          log.error("Field " PTR_FORMAT " of live obj " PTR_FORMAT " in region [" PTR_FORMAT ", " PTR_FORMAT ")",
+            p2i(p), p2i(_containing_obj), p2i(from->bottom()), p2i(from->end()));
+          LogStream ls(log.error());
+          print_object(&ls, _containing_obj);
+          log.error("points to dead obj " PTR_FORMAT " in region [" PTR_FORMAT ", " PTR_FORMAT ")",
+            p2i(obj), p2i(to->bottom()), p2i(to->end()));
+          print_object(&ls, obj);
+        }
+        log.error("----------");
+        _failures = true;
+        failed = true;
+        _n_failures++;
+      }
+    }
+  }
+};
+
+class VerifyRemSetClosure : public G1VerificationClosure {
+public:
+  VerifyRemSetClosure(G1CollectedHeap* g1h, VerifyOption vo) : G1VerificationClosure(g1h, vo) {}
+  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
+  virtual void do_oop(oop* p) { do_oop_work(p); }
+
+  template <class T>
+  void do_oop_work(T* p) {
+    assert(_containing_obj != NULL, "Precondition");
+    assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
+      "Precondition");
+    verify_remembered_set(p);
+  }
+
+  template <class T>
+  void verify_remembered_set(T* p) {
+    T heap_oop = oopDesc::load_heap_oop(p);
+    Log(gc, verify) log;
+    if (!oopDesc::is_null(heap_oop)) {
+      oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
+      HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
+      HeapRegion* to = _g1h->heap_region_containing(obj);
+      if (from != NULL && to != NULL &&
+        from != to &&
+        !to->is_pinned()) {
+        jbyte cv_obj = *_bs->byte_for_const(_containing_obj);
+        jbyte cv_field = *_bs->byte_for_const(p);
+        const jbyte dirty = CardTableModRefBS::dirty_card_val();
+
+        bool is_bad = !(from->is_young()
+          || to->rem_set()->contains_reference(p)
+          || (_containing_obj->is_objArray() ?
+                cv_field == dirty :
+                cv_obj == dirty || cv_field == dirty));
+        if (is_bad) {
+          MutexLockerEx x(ParGCRareEvent_lock,
+            Mutex::_no_safepoint_check_flag);
+
+          if (!_failures) {
+            log.error("----------");
+          }
+          log.error("Missing rem set entry:");
+          log.error("Field " PTR_FORMAT " of obj " PTR_FORMAT ", in region " HR_FORMAT,
+            p2i(p), p2i(_containing_obj), HR_FORMAT_PARAMS(from));
+          ResourceMark rm;
+          LogStream ls(log.error());
+          _containing_obj->print_on(&ls);
+          log.error("points to obj " PTR_FORMAT " in region " HR_FORMAT, p2i(obj), HR_FORMAT_PARAMS(to));
+          if (oopDesc::is_oop(obj)) {
+            obj->print_on(&ls);
+          }
+          log.error("Obj head CTE = %d, field CTE = %d.", cv_obj, cv_field);
+          log.error("----------");
+          _failures = true;
+          _n_failures++;
+        }
+      }
+    }
+  }
+};
+
+// Closure that applies the given two closures in sequence.
+class G1Mux2Closure : public OopClosure {
+  OopClosure* _c1;
+  OopClosure* _c2;
+public:
+  G1Mux2Closure(OopClosure *c1, OopClosure *c2) { _c1 = c1; _c2 = c2; }
+  template <class T> inline void do_oop_work(T* p) {
+    // Apply first closure; then apply the second.
+    _c1->do_oop(p);
+    _c2->do_oop(p);
+  }
+  virtual inline void do_oop(oop* p) { do_oop_work(p); }
+  virtual inline void do_oop(narrowOop* p) { do_oop_work(p); }
+};
+
+// This really ought to be commoned up into OffsetTableContigSpace somehow.
+// We would need a mechanism to make that code skip dead objects.
+
+void HeapRegion::verify(VerifyOption vo,
+                        bool* failures) const {
+  G1CollectedHeap* g1 = G1CollectedHeap::heap();
+  *failures = false;
+  HeapWord* p = bottom();
+  HeapWord* prev_p = NULL;
+  VerifyLiveClosure vl_cl(g1, vo);
+  VerifyRemSetClosure vr_cl(g1, vo);
+  bool is_region_humongous = is_humongous();
+  size_t object_num = 0;
+  while (p < top()) {
+    oop obj = oop(p);
+    size_t obj_size = block_size(p);
+    object_num += 1;
+
+    if (!g1->is_obj_dead_cond(obj, this, vo)) {
+      if (oopDesc::is_oop(obj)) {
+        Klass* klass = obj->klass();
+        bool is_metaspace_object = Metaspace::contains(klass) ||
+                                   (vo == VerifyOption_G1UsePrevMarking &&
+                                   ClassLoaderDataGraph::unload_list_contains(klass));
+        if (!is_metaspace_object) {
+          log_error(gc, verify)("klass " PTR_FORMAT " of object " PTR_FORMAT " "
+                                "not metadata", p2i(klass), p2i(obj));
+          *failures = true;
+          return;
+        } else if (!klass->is_klass()) {
+          log_error(gc, verify)("klass " PTR_FORMAT " of object " PTR_FORMAT " "
+                                "not a klass", p2i(klass), p2i(obj));
+          *failures = true;
+          return;
+        } else {
+          vl_cl.set_containing_obj(obj);
+          if (!g1->collector_state()->full_collection() || G1VerifyRSetsDuringFullGC) {
+            // verify liveness and rem_set
+            vr_cl.set_containing_obj(obj);
+            G1Mux2Closure mux(&vl_cl, &vr_cl);
+            obj->oop_iterate_no_header(&mux);
+
+            if (vr_cl.failures()) {
+              *failures = true;
+            }
+            if (G1MaxVerifyFailures >= 0 &&
+              vr_cl.n_failures() >= G1MaxVerifyFailures) {
+              return;
+            }
+          } else {
+            // verify only liveness
+            obj->oop_iterate_no_header(&vl_cl);
+          }
+          if (vl_cl.failures()) {
+            *failures = true;
+          }
+          if (G1MaxVerifyFailures >= 0 &&
+              vl_cl.n_failures() >= G1MaxVerifyFailures) {
+            return;
+          }
+        }
+      } else {
+        log_error(gc, verify)(PTR_FORMAT " not an oop", p2i(obj));
+        *failures = true;
+        return;
+      }
+    }
+    prev_p = p;
+    p += obj_size;
+  }
+
+  if (!is_young() && !is_empty()) {
+    _bot_part.verify();
+  }
+
+  if (is_region_humongous) {
+    oop obj = oop(this->humongous_start_region()->bottom());
+    if ((HeapWord*)obj > bottom() || (HeapWord*)obj + obj->size() < bottom()) {
+      log_error(gc, verify)("this humongous region is not part of its' humongous object " PTR_FORMAT, p2i(obj));
+      *failures = true;
+      return;
+    }
+  }
+
+  if (!is_region_humongous && p != top()) {
+    log_error(gc, verify)("end of last object " PTR_FORMAT " "
+                          "does not match top " PTR_FORMAT, p2i(p), p2i(top()));
+    *failures = true;
+    return;
+  }
+
+  HeapWord* the_end = end();
+  // Do some extra BOT consistency checking for addresses in the
+  // range [top, end). BOT look-ups in this range should yield
+  // top. No point in doing that if top == end (there's nothing there).
+  if (p < the_end) {
+    // Look up top
+    HeapWord* addr_1 = p;
+    HeapWord* b_start_1 = _bot_part.block_start_const(addr_1);
+    if (b_start_1 != p) {
+      log_error(gc, verify)("BOT look up for top: " PTR_FORMAT " "
+                            " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
+                            p2i(addr_1), p2i(b_start_1), p2i(p));
+      *failures = true;
+      return;
+    }
+
+    // Look up top + 1
+    HeapWord* addr_2 = p + 1;
+    if (addr_2 < the_end) {
+      HeapWord* b_start_2 = _bot_part.block_start_const(addr_2);
+      if (b_start_2 != p) {
+        log_error(gc, verify)("BOT look up for top + 1: " PTR_FORMAT " "
+                              " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
+                              p2i(addr_2), p2i(b_start_2), p2i(p));
+        *failures = true;
+        return;
+      }
+    }
+
+    // Look up an address between top and end
+    size_t diff = pointer_delta(the_end, p) / 2;
+    HeapWord* addr_3 = p + diff;
+    if (addr_3 < the_end) {
+      HeapWord* b_start_3 = _bot_part.block_start_const(addr_3);
+      if (b_start_3 != p) {
+        log_error(gc, verify)("BOT look up for top + diff: " PTR_FORMAT " "
+                              " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
+                              p2i(addr_3), p2i(b_start_3), p2i(p));
+        *failures = true;
+        return;
+      }
+    }
+
+    // Look up end - 1
+    HeapWord* addr_4 = the_end - 1;
+    HeapWord* b_start_4 = _bot_part.block_start_const(addr_4);
+    if (b_start_4 != p) {
+      log_error(gc, verify)("BOT look up for end - 1: " PTR_FORMAT " "
+                            " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
+                            p2i(addr_4), p2i(b_start_4), p2i(p));
+      *failures = true;
+      return;
+    }
+  }
+
+  verify_strong_code_roots(vo, failures);
+}
+
+void HeapRegion::verify() const {
+  bool dummy = false;
+  verify(VerifyOption_G1UsePrevMarking, /* failures */ &dummy);
+}
+
+void HeapRegion::verify_rem_set(VerifyOption vo, bool* failures) const {
+  G1CollectedHeap* g1 = G1CollectedHeap::heap();
+  *failures = false;
+  HeapWord* p = bottom();
+  HeapWord* prev_p = NULL;
+  VerifyRemSetClosure vr_cl(g1, vo);
+  while (p < top()) {
+    oop obj = oop(p);
+    size_t obj_size = block_size(p);
+
+    if (!g1->is_obj_dead_cond(obj, this, vo)) {
+      if (oopDesc::is_oop(obj)) {
+        vr_cl.set_containing_obj(obj);
+        obj->oop_iterate_no_header(&vr_cl);
+
+        if (vr_cl.failures()) {
+          *failures = true;
+        }
+        if (G1MaxVerifyFailures >= 0 &&
+          vr_cl.n_failures() >= G1MaxVerifyFailures) {
+          return;
+        }
+      } else {
+        log_error(gc, verify)(PTR_FORMAT " not an oop", p2i(obj));
+        *failures = true;
+        return;
+      }
+    }
+
+    prev_p = p;
+    p += obj_size;
+  }
+}
+
+void HeapRegion::verify_rem_set() const {
+  bool failures = false;
+  verify_rem_set(VerifyOption_G1UsePrevMarking, &failures);
+  guarantee(!failures, "HeapRegion RemSet verification failed");
+}
+
+void HeapRegion::prepare_for_compaction(CompactPoint* cp) {
+  scan_and_forward(this, cp);
+}
+
+// G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go
+// away eventually.
+
+void G1ContiguousSpace::clear(bool mangle_space) {
+  set_top(bottom());
+  CompactibleSpace::clear(mangle_space);
+  reset_bot();
+}
+
+#ifndef PRODUCT
+void G1ContiguousSpace::mangle_unused_area() {
+  mangle_unused_area_complete();
+}
+
+void G1ContiguousSpace::mangle_unused_area_complete() {
+  SpaceMangler::mangle_region(MemRegion(top(), end()));
+}
+#endif
+
+void G1ContiguousSpace::print() const {
+  print_short();
+  tty->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
+                INTPTR_FORMAT ", " INTPTR_FORMAT ")",
+                p2i(bottom()), p2i(top()), p2i(_bot_part.threshold()), p2i(end()));
+}
+
+HeapWord* G1ContiguousSpace::initialize_threshold() {
+  return _bot_part.initialize_threshold();
+}
+
+HeapWord* G1ContiguousSpace::cross_threshold(HeapWord* start,
+                                                    HeapWord* end) {
+  _bot_part.alloc_block(start, end);
+  return _bot_part.threshold();
+}
+
+void G1ContiguousSpace::record_timestamp() {
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
+  uint curr_gc_time_stamp = g1h->get_gc_time_stamp();
+
+  if (_gc_time_stamp < curr_gc_time_stamp) {
+    _gc_time_stamp = curr_gc_time_stamp;
+  }
+}
+
+void G1ContiguousSpace::safe_object_iterate(ObjectClosure* blk) {
+  object_iterate(blk);
+}
+
+void G1ContiguousSpace::object_iterate(ObjectClosure* blk) {
+  HeapWord* p = bottom();
+  while (p < top()) {
+    if (block_is_obj(p)) {
+      blk->do_object(oop(p));
+    }
+    p += block_size(p);
+  }
+}
+
+G1ContiguousSpace::G1ContiguousSpace(G1BlockOffsetTable* bot) :
+  _bot_part(bot, this),
+  _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true),
+  _gc_time_stamp(0)
+{
+}
+
+void G1ContiguousSpace::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
+  CompactibleSpace::initialize(mr, clear_space, mangle_space);
+  _top = bottom();
+  set_saved_mark_word(NULL);
+  reset_bot();
+}