view src/share/vm/gc_implementation/g1/heapRegion.cpp @ 5986:b86041bd7b99

8010722: assert: failed: heap size is too big for compressed oops Summary: Use conservative assumptions of required alignment for the various garbage collector components into account when determining the maximum heap size that supports compressed oops. Using this conservative value avoids several circular dependencies in the calculation. Reviewed-by: stefank, dholmes
author tschatzl
date Tue, 18 Apr 2017 06:37:32 +0100
parents 05e7f9c0c822
children
line wrap: on
line source
/*
 * 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
 * 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_implementation/g1/g1BlockOffsetTable.inline.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1OopClosures.inline.hpp"
#include "gc_implementation/g1/heapRegion.inline.hpp"
#include "gc_implementation/g1/heapRegionRemSet.hpp"
#include "gc_implementation/g1/heapRegionSeq.inline.hpp"
#include "memory/genOopClosures.inline.hpp"
#include "memory/iterator.hpp"
#include "oops/oop.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;

HeapRegionDCTOC::HeapRegionDCTOC(G1CollectedHeap* g1,
                                 HeapRegion* hr, OopClosure* cl,
                                 CardTableModRefBS::PrecisionStyle precision,
                                 FilterKind fk) :
  ContiguousSpaceDCTOC(hr, cl, precision, NULL),
  _hr(hr), _fk(fk), _g1(g1) { }

FilterOutOfRegionClosure::FilterOutOfRegionClosure(HeapRegion* r,
                                                   OopClosure* oc) :
  _r_bottom(r->bottom()), _r_end(r->end()), _oc(oc) { }

template<class ClosureType>
HeapWord* walk_mem_region_loop(ClosureType* cl, G1CollectedHeap* g1h,
                               HeapRegion* hr,
                               HeapWord* cur, HeapWord* top) {
  oop cur_oop = oop(cur);
  int oop_size = cur_oop->size();
  HeapWord* next_obj = cur + oop_size;
  while (next_obj < top) {
    // Keep filtering the remembered set.
    if (!g1h->is_obj_dead(cur_oop, hr)) {
      // Bottom lies entirely below top, so we can call the
      // non-memRegion version of oop_iterate below.
      cur_oop->oop_iterate(cl);
    }
    cur = next_obj;
    cur_oop = oop(cur);
    oop_size = cur_oop->size();
    next_obj = cur + oop_size;
  }
  return cur;
}

void HeapRegionDCTOC::walk_mem_region_with_cl(MemRegion mr,
                                              HeapWord* bottom,
                                              HeapWord* top,
                                              OopClosure* cl) {
  G1CollectedHeap* g1h = _g1;
  int oop_size;
  OopClosure* cl2 = NULL;

  FilterIntoCSClosure intoCSFilt(this, g1h, cl);
  FilterOutOfRegionClosure outOfRegionFilt(_hr, cl);

  switch (_fk) {
  case NoFilterKind:          cl2 = cl; break;
  case IntoCSFilterKind:      cl2 = &intoCSFilt; break;
  case OutOfRegionFilterKind: cl2 = &outOfRegionFilt; break;
  default:                    ShouldNotReachHere();
  }

  // Start filtering what we add to the remembered set. If the object is
  // not considered dead, either because it is marked (in the mark bitmap)
  // or it was allocated after marking finished, then we add it. Otherwise
  // we can safely ignore the object.
  if (!g1h->is_obj_dead(oop(bottom), _hr)) {
    oop_size = oop(bottom)->oop_iterate(cl2, mr);
  } else {
    oop_size = oop(bottom)->size();
  }

  bottom += oop_size;

  if (bottom < top) {
    // We replicate the loop below for several kinds of possible filters.
    switch (_fk) {
    case NoFilterKind:
      bottom = walk_mem_region_loop(cl, g1h, _hr, bottom, top);
      break;

    case IntoCSFilterKind: {
      FilterIntoCSClosure filt(this, g1h, cl);
      bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
      break;
    }

    case OutOfRegionFilterKind: {
      FilterOutOfRegionClosure filt(_hr, cl);
      bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
      break;
    }

    default:
      ShouldNotReachHere();
    }

    // Last object. Need to do dead-obj filtering here too.
    if (!g1h->is_obj_dead(oop(bottom), _hr)) {
      oop(bottom)->oop_iterate(cl2, mr);
    }
  }
}

// Minimum region size; we won't go lower than that.
// We might want to decrease this in the future, to deal with small
// heaps a bit more efficiently.
#define MIN_REGION_SIZE  (      1024 * 1024 )

// Maximum region size; we don't go higher than that. There's a good
// reason for having an upper bound. We don't want regions to get too
// large, otherwise cleanup's effectiveness would decrease as there
// will be fewer opportunities to find totally empty regions after
// marking.
#define MAX_REGION_SIZE  ( 32 * 1024 * 1024 )

// The automatic region size calculation will try to have around this
// many regions in the heap (based on the min heap size).
#define TARGET_REGION_NUMBER          2048

size_t HeapRegion::max_region_size() {
  return (size_t)MAX_REGION_SIZE;
}

void HeapRegion::setup_heap_region_size(uintx min_heap_size) {
  // region_size in bytes
  uintx region_size = G1HeapRegionSize;
  if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
    // We base the automatic calculation on the min heap size. This
    // can be problematic if the spread between min and max is quite
    // wide, imagine -Xms128m -Xmx32g. But, if we decided it based on
    // the max size, the region size might be way too large for the
    // min size. Either way, some users might have to set the region
    // size manually for some -Xms / -Xmx combos.

    region_size = MAX2(min_heap_size / TARGET_REGION_NUMBER,
                       (uintx) MIN_REGION_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 = ((uintx)1 << region_size_log);

  // Now make sure that we don't go over or under our limits.
  if (region_size < MIN_REGION_SIZE) {
    region_size = MIN_REGION_SIZE;
  } else if (region_size > MAX_REGION_SIZE) {
    region_size = MAX_REGION_SIZE;
  }

  if (region_size != G1HeapRegionSize) {
    // Update the flag to make sure that PrintFlagsFinal logs the correct value
    FLAG_SET_ERGO(uintx, G1HeapRegionSize, region_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 = (size_t)region_size;

  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;
}

void HeapRegion::reset_after_compaction() {
  G1OffsetTableContigSpace::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 par, bool clear_space) {
  assert(_humongous_type == NotHumongous,
         "we should have already filtered out humongous regions");
  assert(_humongous_start_region == NULL,
         "we should have already filtered out humongous regions");
  assert(_end == _orig_end,
         "we should have already filtered out humongous regions");

  _in_collection_set = false;

  set_young_index_in_cset(-1);
  uninstall_surv_rate_group();
  set_young_type(NotYoung);
  reset_pre_dummy_top();

  if (!par) {
    // If this is parallel, this will be done later.
    HeapRegionRemSet* hrrs = rem_set();
    hrrs->clear();
    _claimed = InitialClaimValue;
  }
  zero_marked_bytes();

  _offsets.resize(HeapRegion::GrainWords);
  init_top_at_mark_start();
  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 =
                   (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();
  G1CollectorPolicy* 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_startsHumongous(HeapWord* new_top, HeapWord* new_end) {
  assert(!isHumongous(), "sanity / pre-condition");
  assert(end() == _orig_end,
         "Should be normal before the humongous object allocation");
  assert(top() == bottom(), "should be empty");
  assert(bottom() <= new_top && new_top <= new_end, "pre-condition");

  _humongous_type = StartsHumongous;
  _humongous_start_region = this;

  set_end(new_end);
  _offsets.set_for_starts_humongous(new_top);
}

void HeapRegion::set_continuesHumongous(HeapRegion* first_hr) {
  assert(!isHumongous(), "sanity / pre-condition");
  assert(end() == _orig_end,
         "Should be normal before the humongous object allocation");
  assert(top() == bottom(), "should be empty");
  assert(first_hr->startsHumongous(), "pre-condition");

  _humongous_type = ContinuesHumongous;
  _humongous_start_region = first_hr;
}

void HeapRegion::set_notHumongous() {
  assert(isHumongous(), "pre-condition");

  if (startsHumongous()) {
    assert(top() <= end(), "pre-condition");
    set_end(_orig_end);
    if (top() > end()) {
      // at least one "continues humongous" region after it
      set_top(end());
    }
  } else {
    // continues humongous
    assert(end() == _orig_end, "sanity");
  }

  assert(capacity() == HeapRegion::GrainBytes, "pre-condition");
  _humongous_type = NotHumongous;
  _humongous_start_region = NULL;
}

bool HeapRegion::claimHeapRegion(jint claimValue) {
  jint current = _claimed;
  if (current != claimValue) {
    jint res = Atomic::cmpxchg(claimValue, &_claimed, current);
    if (res == current) {
      return true;
    }
  }
  return false;
}

HeapWord* HeapRegion::next_block_start_careful(HeapWord* addr) {
  HeapWord* low = addr;
  HeapWord* high = end();
  while (low < high) {
    size_t diff = pointer_delta(high, low);
    // Must add one below to bias toward the high amount.  Otherwise, if
  // "high" were at the desired value, and "low" were one less, we
    // would not converge on "high".  This is not symmetric, because
    // we set "high" to a block start, which might be the right one,
    // which we don't do for "low".
    HeapWord* middle = low + (diff+1)/2;
    if (middle == high) return high;
    HeapWord* mid_bs = block_start_careful(middle);
    if (mid_bs < addr) {
      low = middle;
    } else {
      high = mid_bs;
    }
  }
  assert(low == high && low >= addr, "Didn't work.");
  return low;
}

void HeapRegion::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
  G1OffsetTableContigSpace::initialize(mr, false, mangle_space);
  hr_clear(false/*par*/, clear_space);
}
#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
#endif // _MSC_VER


HeapRegion::HeapRegion(uint hrs_index,
                       G1BlockOffsetSharedArray* sharedOffsetArray,
                       MemRegion mr, bool is_zeroed) :
    G1OffsetTableContigSpace(sharedOffsetArray, mr, is_zeroed),
    _hrs_index(hrs_index),
    _humongous_type(NotHumongous), _humongous_start_region(NULL),
    _in_collection_set(false),
    _next_in_special_set(NULL), _orig_end(NULL),
    _claimed(InitialClaimValue), _evacuation_failed(false),
    _prev_marked_bytes(0), _next_marked_bytes(0), _gc_efficiency(0.0),
    _young_type(NotYoung), _next_young_region(NULL),
    _next_dirty_cards_region(NULL), _next(NULL), _pending_removal(false),
#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),
    _predicted_bytes_to_copy(0)
{
  _rem_set = new HeapRegionRemSet(sharedOffsetArray, this);
  _orig_end = mr.end();
  // Note that initialize() will set the start of the unmarked area of the
  // region.
  this->initialize(mr, !is_zeroed, SpaceDecorator::Mangle);
  set_top(bottom());
  set_saved_mark();

  assert(HeapRegionRemSet::num_par_rem_sets() > 0, "Invariant.");
}

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;
}

void HeapRegion::save_marks() {
  set_saved_mark();
}

void HeapRegion::oops_in_mr_iterate(MemRegion mr, OopClosure* cl) {
  HeapWord* p = mr.start();
  HeapWord* e = mr.end();
  oop obj;
  while (p < e) {
    obj = oop(p);
    p += obj->oop_iterate(cl);
  }
  assert(p == e, "bad memregion: doesn't end on obj boundary");
}

#define HeapRegion_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
void HeapRegion::oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
  ContiguousSpace::oop_since_save_marks_iterate##nv_suffix(cl);              \
}
SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(HeapRegion_OOP_SINCE_SAVE_MARKS_DEFN)


void HeapRegion::oop_before_save_marks_iterate(OopClosure* cl) {
  oops_in_mr_iterate(MemRegion(bottom(), saved_mark_word()), cl);
}

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_top_at_mark_start = top();
  _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(bool during_initial_mark,
                                                  bool during_conc_mark,
                                                  size_t marked_bytes) {
  assert(0 <= marked_bytes && marked_bytes <= used(),
         err_msg("marked: "SIZE_FORMAT" used: "SIZE_FORMAT,
                 marked_bytes, used()));
  _prev_marked_bytes = marked_bytes;
}

HeapWord*
HeapRegion::object_iterate_mem_careful(MemRegion mr,
                                                 ObjectClosure* cl) {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  // We used to use "block_start_careful" here.  But we're actually happy
  // to update the BOT while we do this...
  HeapWord* cur = block_start(mr.start());
  mr = mr.intersection(used_region());
  if (mr.is_empty()) return NULL;
  // Otherwise, find the obj that extends onto mr.start().

  assert(cur <= mr.start()
         && (oop(cur)->klass_or_null() == NULL ||
             cur + oop(cur)->size() > mr.start()),
         "postcondition of block_start");
  oop obj;
  while (cur < mr.end()) {
    obj = oop(cur);
    if (obj->klass_or_null() == NULL) {
      // Ran into an unparseable point.
      return cur;
    } else if (!g1h->is_obj_dead(obj)) {
      cl->do_object(obj);
    }
    if (cl->abort()) return cur;
    // The check above must occur before the operation below, since an
    // abort might invalidate the "size" operation.
    cur += obj->size();
  }
  return NULL;
}

HeapWord*
HeapRegion::
oops_on_card_seq_iterate_careful(MemRegion mr,
                                 FilterOutOfRegionClosure* cl,
                                 bool filter_young,
                                 jbyte* card_ptr) {
  // Currently, we should only have to clean the card if filter_young
  // is true and vice versa.
  if (filter_young) {
    assert(card_ptr != NULL, "pre-condition");
  } else {
    assert(card_ptr == NULL, "pre-condition");
  }
  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  // If we're within a stop-world GC, then we might look at a card in a
  // GC alloc region that extends onto a GC LAB, which may not be
  // parseable.  Stop such at the "saved_mark" of the region.
  if (g1h->is_gc_active()) {
    mr = mr.intersection(used_region_at_save_marks());
  } else {
    mr = mr.intersection(used_region());
  }
  if (mr.is_empty()) return NULL;
  // Otherwise, find the obj that extends onto mr.start().

  // The intersection of the incoming mr (for the card) and the
  // allocated part of the region is non-empty. This implies that
  // we have actually allocated into this region. The code in
  // G1CollectedHeap.cpp that allocates a new region sets the
  // is_young tag on the region before allocating. Thus we
  // safely know if this region is young.
  if (is_young() && filter_young) {
    return NULL;
  }

  assert(!is_young(), "check value of filter_young");

  // We can only clean the card here, after we make the decision that
  // the card is not young. And we only clean the card if we have been
  // asked to (i.e., card_ptr != NULL).
  if (card_ptr != NULL) {
    *card_ptr = CardTableModRefBS::clean_card_val();
    // We must complete this write before we do any of the reads below.
    OrderAccess::storeload();
  }

  // Cache the boundaries of the memory region in some const locals
  HeapWord* const start = mr.start();
  HeapWord* const end = mr.end();

  // We used to use "block_start_careful" here.  But we're actually happy
  // to update the BOT while we do this...
  HeapWord* cur = block_start(start);
  assert(cur <= start, "Postcondition");

  oop obj;

  HeapWord* next = cur;
  while (next <= start) {
    cur = next;
    obj = oop(cur);
    if (obj->klass_or_null() == NULL) {
      // Ran into an unparseable point.
      return cur;
    }
    // Otherwise...
    next = (cur + obj->size());
  }

  // If we finish the above loop...We have a parseable object that
  // begins on or before the start of the memory region, and ends
  // inside or spans the entire region.

  assert(obj == oop(cur), "sanity");
  assert(cur <= start &&
         obj->klass_or_null() != NULL &&
         (cur + obj->size()) > start,
         "Loop postcondition");

  if (!g1h->is_obj_dead(obj)) {
    obj->oop_iterate(cl, mr);
  }

  while (cur < end) {
    obj = oop(cur);
    if (obj->klass_or_null() == NULL) {
      // Ran into an unparseable point.
      return cur;
    };

    // Otherwise:
    next = (cur + obj->size());

    if (!g1h->is_obj_dead(obj)) {
      if (next < end || !obj->is_objArray()) {
        // This object either does not span the MemRegion
        // boundary, or if it does it's not an array.
        // Apply closure to whole object.
        obj->oop_iterate(cl);
      } else {
        // This obj is an array that spans the boundary.
        // Stop at the boundary.
        obj->oop_iterate(cl, mr);
      }
    }
    cur = next;
  }
  return NULL;
}

// Code roots support

void HeapRegion::add_strong_code_root(nmethod* nm) {
  HeapRegionRemSet* hrrs = rem_set();
  hrrs->add_strong_code_root(nm);
}

void HeapRegion::remove_strong_code_root(nmethod* nm) {
  HeapRegionRemSet* hrrs = rem_set();
  hrrs->remove_strong_code_root(nm);
}

void HeapRegion::migrate_strong_code_roots() {
  assert(in_collection_set(), "only collection set regions");
  assert(!isHumongous(),
          err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
                  HR_FORMAT_PARAMS(this)));

  HeapRegionRemSet* hrrs = rem_set();
  hrrs->migrate_strong_code_roots();
}

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;
  nmethod* _nm;
  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
          gclog_or_tty->print_cr("Object "PTR_FORMAT" in region "
                                 "["PTR_FORMAT", "PTR_FORMAT") is above "
                                 "top "PTR_FORMAT,
                                 obj, _hr->bottom(), _hr->end(), _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, nmethod* nm):
    _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_nmethod_or_null();
    if (nm != NULL) {
      // Verify that the nemthod is live
      if (!nm->is_alive()) {
        gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has dead nmethod "
                               PTR_FORMAT" in its strong code roots",
                               _hr->bottom(), _hr->end(), nm);
        _failures = true;
      } else {
        VerifyStrongCodeRootOopClosure oop_cl(_hr, nm);
        nm->oops_do(&oop_cl);
        if (!oop_cl.has_oops_in_region()) {
          gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has nmethod "
                                 PTR_FORMAT" in its strong code roots "
                                 "with no pointers into region",
                                 _hr->bottom(), _hr->end(), nm);
          _failures = true;
        } else if (oop_cl.failures()) {
          gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has other "
                                 "failures for nmethod "PTR_FORMAT,
                                 _hr->bottom(), _hr->end(), 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();
  int 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) {
      gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is empty "
                             "but has "INT32_FORMAT" code root entries",
                             bottom(), end(), strong_code_roots_length);
      *failures = true;
    }
    return;
  }

  if (continuesHumongous()) {
    if (strong_code_roots_length > 0) {
      gclog_or_tty->print_cr("region "HR_FORMAT" is a continuation of a humongous "
                             "region but has "INT32_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(gclog_or_tty); }
void HeapRegion::print_on(outputStream* st) const {
  if (isHumongous()) {
    if (startsHumongous())
      st->print(" HS");
    else
      st->print(" HC");
  } else {
    st->print("   ");
  }
  if (in_collection_set())
    st->print(" CS");
  else
    st->print("   ");
  if (is_young())
    st->print(is_survivor() ? " SU" : " Y ");
  else
    st->print("   ");
  if (is_empty())
    st->print(" F");
  else
    st->print("  ");
  st->print(" TS %5d", _gc_time_stamp);
  st->print(" PTAMS "PTR_FORMAT" NTAMS "PTR_FORMAT,
            prev_top_at_mark_start(), next_top_at_mark_start());
  G1OffsetTableContigSpace::print_on(st);
}

class VerifyLiveClosure: public OopClosure {
private:
  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.
  VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) :
    _g1h(g1h), _bs(NULL), _containing_obj(NULL),
    _failures(false), _n_failures(0), _vo(vo)
  {
    BarrierSet* bs = _g1h->barrier_set();
    if (bs->is_a(BarrierSet::CardTableModRef))
      _bs = (CardTableModRefBS*)bs;
  }

  void set_containing_obj(oop obj) {
    _containing_obj = obj;
  }

  bool failures() { return _failures; }
  int n_failures() { return _n_failures; }

  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  virtual void do_oop(      oop* p) { do_oop_work(p); }

  void print_object(outputStream* out, oop obj) {
#ifdef PRODUCT
    klassOop k = obj->klass();
    const char* class_name = instanceKlass::cast(k)->external_name();
    out->print_cr("class name %s", class_name);
#else // PRODUCT
    obj->print_on(out);
#endif // PRODUCT
  }

  template <class T>
  void do_oop_work(T* p) {
    assert(_containing_obj != NULL, "Precondition");
    assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
           "Precondition");
    T heap_oop = oopDesc::load_heap_oop(p);
    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) {
          gclog_or_tty->print_cr("");
          gclog_or_tty->print_cr("----------");
        }
        if (!_g1h->is_in_closed_subset(obj)) {
          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
          gclog_or_tty->print_cr("Field "PTR_FORMAT
                                 " of live obj "PTR_FORMAT" in region "
                                 "["PTR_FORMAT", "PTR_FORMAT")",
                                 p, (void*) _containing_obj,
                                 from->bottom(), from->end());
          print_object(gclog_or_tty, _containing_obj);
          gclog_or_tty->print_cr("points to obj "PTR_FORMAT" not in the heap",
                                 (void*) obj);
        } else {
          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
          HeapRegion* to   = _g1h->heap_region_containing((HeapWord*)obj);
          gclog_or_tty->print_cr("Field "PTR_FORMAT
                                 " of live obj "PTR_FORMAT" in region "
                                 "["PTR_FORMAT", "PTR_FORMAT")",
                                 p, (void*) _containing_obj,
                                 from->bottom(), from->end());
          print_object(gclog_or_tty, _containing_obj);
          gclog_or_tty->print_cr("points to dead obj "PTR_FORMAT" in region "
                                 "["PTR_FORMAT", "PTR_FORMAT")",
                                 (void*) obj, to->bottom(), to->end());
          print_object(gclog_or_tty, obj);
        }
        gclog_or_tty->print_cr("----------");
        gclog_or_tty->flush();
        _failures = true;
        failed = true;
        _n_failures++;
      }

      if (!_g1h->full_collection() || G1VerifyRSetsDuringFullGC) {
        HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
        HeapRegion* to   = _g1h->heap_region_containing(obj);
        if (from != NULL && to != NULL &&
            from != to &&
            !to->isHumongous()) {
          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)
                          || !G1HRRSFlushLogBuffersOnVerify && // buffers were not flushed
                              (_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) {
              gclog_or_tty->print_cr("");
              gclog_or_tty->print_cr("----------");
            }
            gclog_or_tty->print_cr("Missing rem set entry:");
            gclog_or_tty->print_cr("Field "PTR_FORMAT" "
                                   "of obj "PTR_FORMAT", "
                                   "in region "HR_FORMAT,
                                   p, (void*) _containing_obj,
                                   HR_FORMAT_PARAMS(from));
            _containing_obj->print_on(gclog_or_tty);
            gclog_or_tty->print_cr("points to obj "PTR_FORMAT" "
                                   "in region "HR_FORMAT,
                                   (void*) obj,
                                   HR_FORMAT_PARAMS(to));
            obj->print_on(gclog_or_tty);
            gclog_or_tty->print_cr("Obj head CTE = %d, field CTE = %d.",
                          cv_obj, cv_field);
            gclog_or_tty->print_cr("----------");
            gclog_or_tty->flush();
            _failures = true;
            if (!failed) _n_failures++;
          }
        }
      }
    }
  }
};

// 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);
  bool is_humongous = isHumongous();
  bool do_bot_verify = !is_young();
  size_t object_num = 0;
  while (p < top()) {
    oop obj = oop(p);
    size_t obj_size = obj->size();
    object_num += 1;

    if (is_humongous != g1->isHumongous(obj_size)) {
      gclog_or_tty->print_cr("obj "PTR_FORMAT" is of %shumongous size ("
                             SIZE_FORMAT" words) in a %shumongous region",
                             p, g1->isHumongous(obj_size) ? "" : "non-",
                             obj_size, is_humongous ? "" : "non-");
       *failures = true;
       return;
    }

    // If it returns false, verify_for_object() will output the
    // appropriate messasge.
    if (do_bot_verify && !_offsets.verify_for_object(p, obj_size)) {
      *failures = true;
      return;
    }

    if (!g1->is_obj_dead_cond(obj, this, vo)) {
      if (obj->is_oop()) {
        klassOop klass = obj->klass();
        if (!klass->is_perm()) {
          gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
                                 "not in perm", klass, obj);
          *failures = true;
          return;
        } else if (!klass->is_klass()) {
          gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
                                 "not a klass", klass, obj);
          *failures = true;
          return;
        } else {
          vl_cl.set_containing_obj(obj);
          obj->oop_iterate(&vl_cl);
          if (vl_cl.failures()) {
            *failures = true;
          }
          if (G1MaxVerifyFailures >= 0 &&
              vl_cl.n_failures() >= G1MaxVerifyFailures) {
            return;
          }
        }
      } else {
        gclog_or_tty->print_cr(PTR_FORMAT" no an oop", obj);
        *failures = true;
        return;
      }
    }
    prev_p = p;
    p += obj_size;
  }

  if (p != top()) {
    gclog_or_tty->print_cr("end of last object "PTR_FORMAT" "
                           "does not match top "PTR_FORMAT, p, top());
    *failures = true;
    return;
  }

  HeapWord* the_end = end();
  assert(p == top(), "it should still hold");
  // 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 = _offsets.block_start_const(addr_1);
    if (b_start_1 != p) {
      gclog_or_tty->print_cr("BOT look up for top: "PTR_FORMAT" "
                             " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
                             addr_1, b_start_1, p);
      *failures = true;
      return;
    }

    // Look up top + 1
    HeapWord* addr_2 = p + 1;
    if (addr_2 < the_end) {
      HeapWord* b_start_2 = _offsets.block_start_const(addr_2);
      if (b_start_2 != p) {
        gclog_or_tty->print_cr("BOT look up for top + 1: "PTR_FORMAT" "
                               " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
                               addr_2, b_start_2, 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 = _offsets.block_start_const(addr_3);
      if (b_start_3 != p) {
        gclog_or_tty->print_cr("BOT look up for top + diff: "PTR_FORMAT" "
                               " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
                               addr_3, b_start_3, p);
        *failures = true;
        return;
      }
    }

    // Loook up end - 1
    HeapWord* addr_4 = the_end - 1;
    HeapWord* b_start_4 = _offsets.block_start_const(addr_4);
    if (b_start_4 != p) {
      gclog_or_tty->print_cr("BOT look up for end - 1: "PTR_FORMAT" "
                             " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
                             addr_4, b_start_4, p);
      *failures = true;
      return;
    }
  }

  if (is_humongous && object_num > 1) {
    gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is humongous "
                           "but has "SIZE_FORMAT", objects",
                           bottom(), end(), object_num);
    *failures = true;
    return;
  }

  verify_strong_code_roots(vo, failures);
}

void HeapRegion::verify() const {
  bool dummy = false;
  verify(VerifyOption_G1UsePrevMarking, /* failures */ &dummy);
}

// G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go
// away eventually.

void G1OffsetTableContigSpace::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
  // false ==> we'll do the clearing if there's clearing to be done.
  ContiguousSpace::initialize(mr, false, mangle_space);
  _offsets.zero_bottom_entry();
  _offsets.initialize_threshold();
  if (clear_space) clear(mangle_space);
}

void G1OffsetTableContigSpace::clear(bool mangle_space) {
  ContiguousSpace::clear(mangle_space);
  _offsets.zero_bottom_entry();
  _offsets.initialize_threshold();
}

void G1OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
  Space::set_bottom(new_bottom);
  _offsets.set_bottom(new_bottom);
}

void G1OffsetTableContigSpace::set_end(HeapWord* new_end) {
  Space::set_end(new_end);
  _offsets.resize(new_end - bottom());
}

void G1OffsetTableContigSpace::print() const {
  print_short();
  gclog_or_tty->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
                INTPTR_FORMAT ", " INTPTR_FORMAT ")",
                bottom(), top(), _offsets.threshold(), end());
}

HeapWord* G1OffsetTableContigSpace::initialize_threshold() {
  return _offsets.initialize_threshold();
}

HeapWord* G1OffsetTableContigSpace::cross_threshold(HeapWord* start,
                                                    HeapWord* end) {
  _offsets.alloc_block(start, end);
  return _offsets.threshold();
}

HeapWord* G1OffsetTableContigSpace::saved_mark_word() const {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  assert( _gc_time_stamp <= g1h->get_gc_time_stamp(), "invariant" );
  if (_gc_time_stamp < g1h->get_gc_time_stamp())
    return top();
  else
    return ContiguousSpace::saved_mark_word();
}

void G1OffsetTableContigSpace::set_saved_mark() {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  unsigned curr_gc_time_stamp = g1h->get_gc_time_stamp();

  if (_gc_time_stamp < curr_gc_time_stamp) {
    // The order of these is important, as another thread might be
    // about to start scanning this region. If it does so after
    // set_saved_mark and before _gc_time_stamp = ..., then the latter
    // will be false, and it will pick up top() as the high water mark
    // of region. If it does so after _gc_time_stamp = ..., then it
    // will pick up the right saved_mark_word() as the high water mark
    // of the region. Either way, the behaviour will be correct.
    ContiguousSpace::set_saved_mark();
    OrderAccess::storestore();
    _gc_time_stamp = curr_gc_time_stamp;
    // No need to do another barrier to flush the writes above. If
    // this is called in parallel with other threads trying to
    // allocate into the region, the caller should call this while
    // holding a lock and when the lock is released the writes will be
    // flushed.
  }
}

G1OffsetTableContigSpace::
G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
                         MemRegion mr, bool is_zeroed) :
  _offsets(sharedOffsetArray, mr),
  _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true),
  _gc_time_stamp(0)
{
  _offsets.set_space(this);
  initialize(mr, !is_zeroed, SpaceDecorator::Mangle);
}