--- /dev/null	2018-11-26 11:49:18.255023023 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp	2018-11-26 21:30:00.739128959 +0100
@@ -0,0 +1,681 @@
+/*
+ * Copyright (c) 2013, 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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 "memory/allocation.hpp"
+#include "gc/shenandoah/shenandoahBrooksPointer.hpp"
+#include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
+#include "gc/shenandoah/shenandoahHeap.hpp"
+#include "gc/shenandoah/shenandoahHeap.inline.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
+#include "gc/shenandoah/shenandoahTraversalGC.hpp"
+#include "gc/shared/space.inline.hpp"
+#include "memory/iterator.inline.hpp"
+#include "memory/resourceArea.hpp"
+#include "memory/universe.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/java.hpp"
+#include "runtime/mutexLocker.hpp"
+#include "runtime/os.hpp"
+#include "runtime/safepoint.hpp"
+
+size_t ShenandoahHeapRegion::RegionCount = 0;
+size_t ShenandoahHeapRegion::RegionSizeBytes = 0;
+size_t ShenandoahHeapRegion::RegionSizeWords = 0;
+size_t ShenandoahHeapRegion::RegionSizeBytesShift = 0;
+size_t ShenandoahHeapRegion::RegionSizeWordsShift = 0;
+size_t ShenandoahHeapRegion::RegionSizeBytesMask = 0;
+size_t ShenandoahHeapRegion::RegionSizeWordsMask = 0;
+size_t ShenandoahHeapRegion::HumongousThresholdBytes = 0;
+size_t ShenandoahHeapRegion::HumongousThresholdWords = 0;
+size_t ShenandoahHeapRegion::MaxTLABSizeBytes = 0;
+size_t ShenandoahHeapRegion::MaxTLABSizeWords = 0;
+
+ShenandoahHeapRegion::PaddedAllocSeqNum ShenandoahHeapRegion::_alloc_seq_num;
+
+ShenandoahHeapRegion::ShenandoahHeapRegion(ShenandoahHeap* heap, HeapWord* start,
+                                           size_t size_words, size_t index, bool committed) :
+  _heap(heap),
+  _pacer(ShenandoahPacing ? heap->pacer() : NULL),
+  _reserved(MemRegion(start, size_words)),
+  _region_number(index),
+  _new_top(NULL),
+  _critical_pins(0),
+  _empty_time(os::elapsedTime()),
+  _state(committed ? _empty_committed : _empty_uncommitted),
+  _tlab_allocs(0),
+  _gclab_allocs(0),
+  _shared_allocs(0),
+  _seqnum_first_alloc_mutator(0),
+  _seqnum_first_alloc_gc(0),
+  _seqnum_last_alloc_mutator(0),
+  _seqnum_last_alloc_gc(0),
+  _live_data(0) {
+
+  ContiguousSpace::initialize(_reserved, true, committed);
+}
+
+size_t ShenandoahHeapRegion::region_number() const {
+  return _region_number;
+}
+
+void ShenandoahHeapRegion::report_illegal_transition(const char *method) {
+  ResourceMark rm;
+  stringStream ss;
+  ss.print("Illegal region state transition from \"%s\", at %s\n  ", region_state_to_string(_state), method);
+  print_on(&ss);
+  fatal("%s", ss.as_string());
+}
+
+void ShenandoahHeapRegion::make_regular_allocation() {
+  _heap->assert_heaplock_owned_by_current_thread();
+
+  switch (_state) {
+    case _empty_uncommitted:
+      do_commit();
+    case _empty_committed:
+      _state = _regular;
+    case _regular:
+    case _pinned:
+      return;
+    default:
+      report_illegal_transition("regular allocation");
+  }
+}
+
+void ShenandoahHeapRegion::make_regular_bypass() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  assert (_heap->is_full_gc_in_progress() || _heap->is_degenerated_gc_in_progress(),
+          "only for full or degen GC");
+
+  switch (_state) {
+    case _empty_uncommitted:
+      do_commit();
+    case _empty_committed:
+    case _cset:
+    case _humongous_start:
+    case _humongous_cont:
+      _state = _regular;
+      return;
+    case _pinned_cset:
+      _state = _pinned;
+      return;
+    case _regular:
+    case _pinned:
+      return;
+    default:
+      report_illegal_transition("regular bypass");
+  }
+}
+
+void ShenandoahHeapRegion::make_humongous_start() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _empty_uncommitted:
+      do_commit();
+    case _empty_committed:
+      _state = _humongous_start;
+      return;
+    default:
+      report_illegal_transition("humongous start allocation");
+  }
+}
+
+void ShenandoahHeapRegion::make_humongous_start_bypass() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  assert (_heap->is_full_gc_in_progress(), "only for full GC");
+
+  switch (_state) {
+    case _empty_committed:
+    case _regular:
+    case _humongous_start:
+    case _humongous_cont:
+      _state = _humongous_start;
+      return;
+    default:
+      report_illegal_transition("humongous start bypass");
+  }
+}
+
+void ShenandoahHeapRegion::make_humongous_cont() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _empty_uncommitted:
+      do_commit();
+    case _empty_committed:
+      _state = _humongous_cont;
+      return;
+    default:
+      report_illegal_transition("humongous continuation allocation");
+  }
+}
+
+void ShenandoahHeapRegion::make_humongous_cont_bypass() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  assert (_heap->is_full_gc_in_progress(), "only for full GC");
+
+  switch (_state) {
+    case _empty_committed:
+    case _regular:
+    case _humongous_start:
+    case _humongous_cont:
+      _state = _humongous_cont;
+      return;
+    default:
+      report_illegal_transition("humongous continuation bypass");
+  }
+}
+
+void ShenandoahHeapRegion::make_pinned() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _regular:
+      assert (_critical_pins == 0, "sanity");
+      _state = _pinned;
+    case _pinned_cset:
+    case _pinned:
+      _critical_pins++;
+      return;
+    case _humongous_start:
+      assert (_critical_pins == 0, "sanity");
+      _state = _pinned_humongous_start;
+    case _pinned_humongous_start:
+      _critical_pins++;
+      return;
+    case _cset:
+      guarantee(_heap->cancelled_gc(), "only valid when evac has been cancelled");
+      assert (_critical_pins == 0, "sanity");
+      _state = _pinned_cset;
+      _critical_pins++;
+      return;
+    default:
+      report_illegal_transition("pinning");
+  }
+}
+
+void ShenandoahHeapRegion::make_unpinned() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _pinned:
+      assert (_critical_pins > 0, "sanity");
+      _critical_pins--;
+      if (_critical_pins == 0) {
+        _state = _regular;
+      }
+      return;
+    case _regular:
+    case _humongous_start:
+      assert (_critical_pins == 0, "sanity");
+      return;
+    case _pinned_cset:
+      guarantee(_heap->cancelled_gc(), "only valid when evac has been cancelled");
+      assert (_critical_pins > 0, "sanity");
+      _critical_pins--;
+      if (_critical_pins == 0) {
+        _state = _cset;
+      }
+      return;
+    case _pinned_humongous_start:
+      assert (_critical_pins > 0, "sanity");
+      _critical_pins--;
+      if (_critical_pins == 0) {
+        _state = _humongous_start;
+      }
+      return;
+    default:
+      report_illegal_transition("unpinning");
+  }
+}
+
+void ShenandoahHeapRegion::make_cset() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _regular:
+      _state = _cset;
+    case _cset:
+      return;
+    default:
+      report_illegal_transition("cset");
+  }
+}
+
+void ShenandoahHeapRegion::make_trash() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _cset:
+      // Reclaiming cset regions
+    case _humongous_start:
+    case _humongous_cont:
+      // Reclaiming humongous regions
+    case _regular:
+      // Immediate region reclaim
+      _state = _trash;
+      return;
+    default:
+      report_illegal_transition("trashing");
+  }
+}
+
+void ShenandoahHeapRegion::make_trash_immediate() {
+  make_trash();
+
+  // On this path, we know there are no marked objects in the region,
+  // tell marking context about it to bypass bitmap resets.
+  _heap->complete_marking_context()->reset_top_bitmap(this);
+}
+
+void ShenandoahHeapRegion::make_empty() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _trash:
+      _state = _empty_committed;
+      _empty_time = os::elapsedTime();
+      return;
+    default:
+      report_illegal_transition("emptying");
+  }
+}
+
+void ShenandoahHeapRegion::make_uncommitted() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  switch (_state) {
+    case _empty_committed:
+      do_uncommit();
+      _state = _empty_uncommitted;
+      return;
+    default:
+      report_illegal_transition("uncommiting");
+  }
+}
+
+void ShenandoahHeapRegion::make_committed_bypass() {
+  _heap->assert_heaplock_owned_by_current_thread();
+  assert (_heap->is_full_gc_in_progress(), "only for full GC");
+
+  switch (_state) {
+    case _empty_uncommitted:
+      do_commit();
+      _state = _empty_committed;
+      return;
+    default:
+      report_illegal_transition("commit bypass");
+  }
+}
+
+void ShenandoahHeapRegion::clear_live_data() {
+  OrderAccess::release_store_fence<size_t>(&_live_data, 0);
+}
+
+void ShenandoahHeapRegion::reset_alloc_metadata() {
+  _tlab_allocs = 0;
+  _gclab_allocs = 0;
+  _shared_allocs = 0;
+  _seqnum_first_alloc_mutator = 0;
+  _seqnum_last_alloc_mutator = 0;
+  _seqnum_first_alloc_gc = 0;
+  _seqnum_last_alloc_gc = 0;
+}
+
+void ShenandoahHeapRegion::reset_alloc_metadata_to_shared() {
+  if (used() > 0) {
+    _tlab_allocs = 0;
+    _gclab_allocs = 0;
+    _shared_allocs = used() >> LogHeapWordSize;
+    uint64_t next = _alloc_seq_num.value++;
+    _seqnum_first_alloc_mutator = next;
+    _seqnum_last_alloc_mutator = next;
+    _seqnum_first_alloc_gc = 0;
+    _seqnum_last_alloc_gc = 0;
+  } else {
+    reset_alloc_metadata();
+  }
+}
+
+size_t ShenandoahHeapRegion::get_shared_allocs() const {
+  return _shared_allocs * HeapWordSize;
+}
+
+size_t ShenandoahHeapRegion::get_tlab_allocs() const {
+  return _tlab_allocs * HeapWordSize;
+}
+
+size_t ShenandoahHeapRegion::get_gclab_allocs() const {
+  return _gclab_allocs * HeapWordSize;
+}
+
+void ShenandoahHeapRegion::set_live_data(size_t s) {
+  assert(Thread::current()->is_VM_thread(), "by VM thread");
+  _live_data = (s >> LogHeapWordSize);
+}
+
+size_t ShenandoahHeapRegion::get_live_data_words() const {
+  return OrderAccess::load_acquire(&_live_data);
+}
+
+size_t ShenandoahHeapRegion::get_live_data_bytes() const {
+  return get_live_data_words() * HeapWordSize;
+}
+
+bool ShenandoahHeapRegion::has_live() const {
+  return get_live_data_words() != 0;
+}
+
+size_t ShenandoahHeapRegion::garbage() const {
+  assert(used() >= get_live_data_bytes(), "Live Data must be a subset of used() live: " SIZE_FORMAT " used: " SIZE_FORMAT,
+         get_live_data_bytes(), used());
+
+  size_t result = used() - get_live_data_bytes();
+  return result;
+}
+
+void ShenandoahHeapRegion::print_on(outputStream* st) const {
+  st->print("|");
+  st->print(SIZE_FORMAT_W(5), this->_region_number);
+
+  switch (_state) {
+    case _empty_uncommitted:
+      st->print("|EU ");
+      break;
+    case _empty_committed:
+      st->print("|EC ");
+      break;
+    case _regular:
+      st->print("|R  ");
+      break;
+    case _humongous_start:
+      st->print("|H  ");
+      break;
+    case _pinned_humongous_start:
+      st->print("|HP ");
+      break;
+    case _humongous_cont:
+      st->print("|HC ");
+      break;
+    case _cset:
+      st->print("|CS ");
+      break;
+    case _trash:
+      st->print("|T  ");
+      break;
+    case _pinned:
+      st->print("|P  ");
+      break;
+    case _pinned_cset:
+      st->print("|CSP");
+      break;
+    default:
+      ShouldNotReachHere();
+  }
+  st->print("|BTE " INTPTR_FORMAT_W(12) ", " INTPTR_FORMAT_W(12) ", " INTPTR_FORMAT_W(12),
+            p2i(bottom()), p2i(top()), p2i(end()));
+  st->print("|TAMS " INTPTR_FORMAT_W(12),
+            p2i(_heap->marking_context()->top_at_mark_start(const_cast<ShenandoahHeapRegion*>(this))));
+  st->print("|U " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(used()),                proper_unit_for_byte_size(used()));
+  st->print("|T " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_tlab_allocs()),     proper_unit_for_byte_size(get_tlab_allocs()));
+  st->print("|G " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_gclab_allocs()),    proper_unit_for_byte_size(get_gclab_allocs()));
+  st->print("|S " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_shared_allocs()),   proper_unit_for_byte_size(get_shared_allocs()));
+  st->print("|L " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_live_data_bytes()), proper_unit_for_byte_size(get_live_data_bytes()));
+  st->print("|CP " SIZE_FORMAT_W(3), _critical_pins);
+  st->print("|SN " UINT64_FORMAT_HEX_W(12) ", " UINT64_FORMAT_HEX_W(8) ", " UINT64_FORMAT_HEX_W(8) ", " UINT64_FORMAT_HEX_W(8),
+            seqnum_first_alloc_mutator(), seqnum_last_alloc_mutator(),
+            seqnum_first_alloc_gc(), seqnum_last_alloc_gc());
+  st->cr();
+}
+
+void ShenandoahHeapRegion::oop_iterate(OopIterateClosure* blk) {
+  if (!is_active()) return;
+  if (is_humongous()) {
+    oop_iterate_humongous(blk);
+  } else {
+    oop_iterate_objects(blk);
+  }
+}
+
+void ShenandoahHeapRegion::oop_iterate_objects(OopIterateClosure* blk) {
+  assert(! is_humongous(), "no humongous region here");
+  HeapWord* obj_addr = bottom() + ShenandoahBrooksPointer::word_size();
+  HeapWord* t = top();
+  // Could call objects iterate, but this is easier.
+  while (obj_addr < t) {
+    oop obj = oop(obj_addr);
+    obj_addr += obj->oop_iterate_size(blk) + ShenandoahBrooksPointer::word_size();
+  }
+}
+
+void ShenandoahHeapRegion::oop_iterate_humongous(OopIterateClosure* blk) {
+  assert(is_humongous(), "only humongous region here");
+  // Find head.
+  ShenandoahHeapRegion* r = humongous_start_region();
+  assert(r->is_humongous_start(), "need humongous head here");
+  oop obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size());
+  obj->oop_iterate(blk, MemRegion(bottom(), top()));
+}
+
+ShenandoahHeapRegion* ShenandoahHeapRegion::humongous_start_region() const {
+  assert(is_humongous(), "Must be a part of the humongous region");
+  size_t reg_num = region_number();
+  ShenandoahHeapRegion* r = const_cast<ShenandoahHeapRegion*>(this);
+  while (!r->is_humongous_start()) {
+    assert(reg_num > 0, "Sanity");
+    reg_num --;
+    r = _heap->get_region(reg_num);
+    assert(r->is_humongous(), "Must be a part of the humongous region");
+  }
+  assert(r->is_humongous_start(), "Must be");
+  return r;
+}
+
+void ShenandoahHeapRegion::recycle() {
+  ContiguousSpace::clear(false);
+  if (ZapUnusedHeapArea) {
+    ContiguousSpace::mangle_unused_area_complete();
+  }
+  clear_live_data();
+
+  reset_alloc_metadata();
+
+  _heap->marking_context()->reset_top_at_mark_start(this);
+
+  make_empty();
+}
+
+HeapWord* ShenandoahHeapRegion::block_start_const(const void* p) const {
+  assert(MemRegion(bottom(), end()).contains(p),
+         "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
+         p2i(p), p2i(bottom()), p2i(end()));
+  if (p >= top()) {
+    return top();
+  } else {
+    HeapWord* last = bottom() + ShenandoahBrooksPointer::word_size();
+    HeapWord* cur = last;
+    while (cur <= p) {
+      last = cur;
+      cur += oop(cur)->size() + ShenandoahBrooksPointer::word_size();
+    }
+    shenandoah_assert_correct(NULL, oop(last));
+    return last;
+  }
+}
+
+void ShenandoahHeapRegion::setup_sizes(size_t initial_heap_size, size_t max_heap_size) {
+  // Absolute minimums we should not ever break.
+  static const size_t MIN_REGION_SIZE = 256*K;
+
+  if (FLAG_IS_DEFAULT(ShenandoahMinRegionSize)) {
+    FLAG_SET_DEFAULT(ShenandoahMinRegionSize, MIN_REGION_SIZE);
+  }
+
+  size_t region_size;
+  if (FLAG_IS_DEFAULT(ShenandoahHeapRegionSize)) {
+    if (ShenandoahMinRegionSize > initial_heap_size / MIN_NUM_REGIONS) {
+      err_msg message("Initial heap size (" SIZE_FORMAT "K) is too low to afford the minimum number "
+                      "of regions (" SIZE_FORMAT ") of minimum region size (" SIZE_FORMAT "K).",
+                      initial_heap_size/K, MIN_NUM_REGIONS, ShenandoahMinRegionSize/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
+    }
+    if (ShenandoahMinRegionSize < MIN_REGION_SIZE) {
+      err_msg message("" SIZE_FORMAT "K should not be lower than minimum region size (" SIZE_FORMAT "K).",
+                      ShenandoahMinRegionSize/K,  MIN_REGION_SIZE/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
+    }
+    if (ShenandoahMinRegionSize < MinTLABSize) {
+      err_msg message("" SIZE_FORMAT "K should not be lower than TLAB size size (" SIZE_FORMAT "K).",
+                      ShenandoahMinRegionSize/K,  MinTLABSize/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
+    }
+    if (ShenandoahMaxRegionSize < MIN_REGION_SIZE) {
+      err_msg message("" SIZE_FORMAT "K should not be lower than min region size (" SIZE_FORMAT "K).",
+                      ShenandoahMaxRegionSize/K,  MIN_REGION_SIZE/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahMaxRegionSize option", message);
+    }
+    if (ShenandoahMinRegionSize > ShenandoahMaxRegionSize) {
+      err_msg message("Minimum (" SIZE_FORMAT "K) should be larger than maximum (" SIZE_FORMAT "K).",
+                      ShenandoahMinRegionSize/K, ShenandoahMaxRegionSize/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize or -XX:ShenandoahMaxRegionSize", message);
+    }
+
+    // We rapidly expand to max_heap_size in most scenarios, so that is the measure
+    // for usual heap sizes. Do not depend on initial_heap_size here.
+    region_size = max_heap_size / ShenandoahTargetNumRegions;
+
+    // Now make sure that we don't go over or under our limits.
+    region_size = MAX2(ShenandoahMinRegionSize, region_size);
+    region_size = MIN2(ShenandoahMaxRegionSize, region_size);
+
+  } else {
+    if (ShenandoahHeapRegionSize > initial_heap_size / MIN_NUM_REGIONS) {
+      err_msg message("Initial heap size (" SIZE_FORMAT "K) is too low to afford the minimum number "
+                              "of regions (" SIZE_FORMAT ") of requested size (" SIZE_FORMAT "K).",
+                      initial_heap_size/K, MIN_NUM_REGIONS, ShenandoahHeapRegionSize/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
+    }
+    if (ShenandoahHeapRegionSize < ShenandoahMinRegionSize) {
+      err_msg message("Heap region size (" SIZE_FORMAT "K) should be larger than min region size (" SIZE_FORMAT "K).",
+                      ShenandoahHeapRegionSize/K, ShenandoahMinRegionSize/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
+    }
+    if (ShenandoahHeapRegionSize > ShenandoahMaxRegionSize) {
+      err_msg message("Heap region size (" SIZE_FORMAT "K) should be lower than max region size (" SIZE_FORMAT "K).",
+                      ShenandoahHeapRegionSize/K, ShenandoahMaxRegionSize/K);
+      vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
+    }
+    region_size = ShenandoahHeapRegionSize;
+  }
+
+  // Make sure region size is at least one large page, if enabled.
+  // Otherwise, uncommitting one region may falsely uncommit the adjacent
+  // regions too.
+  // Also see shenandoahArguments.cpp, where it handles UseLargePages.
+  if (UseLargePages && ShenandoahUncommit) {
+    region_size = MAX2(region_size, os::large_page_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, set up the globals.
+  guarantee(RegionSizeBytesShift == 0, "we should only set it once");
+  RegionSizeBytesShift = (size_t)region_size_log;
+
+  guarantee(RegionSizeWordsShift == 0, "we should only set it once");
+  RegionSizeWordsShift = RegionSizeBytesShift - LogHeapWordSize;
+
+  guarantee(RegionSizeBytes == 0, "we should only set it once");
+  RegionSizeBytes = region_size;
+  RegionSizeWords = RegionSizeBytes >> LogHeapWordSize;
+  assert (RegionSizeWords*HeapWordSize == RegionSizeBytes, "sanity");
+
+  guarantee(RegionSizeWordsMask == 0, "we should only set it once");
+  RegionSizeWordsMask = RegionSizeWords - 1;
+
+  guarantee(RegionSizeBytesMask == 0, "we should only set it once");
+  RegionSizeBytesMask = RegionSizeBytes - 1;
+
+  guarantee(RegionCount == 0, "we should only set it once");
+  RegionCount = max_heap_size / RegionSizeBytes;
+  guarantee(RegionCount >= MIN_NUM_REGIONS, "Should have at least minimum regions");
+
+  guarantee(HumongousThresholdWords == 0, "we should only set it once");
+  HumongousThresholdWords = RegionSizeWords * ShenandoahHumongousThreshold / 100;
+  assert (HumongousThresholdWords <= RegionSizeWords, "sanity");
+
+  guarantee(HumongousThresholdBytes == 0, "we should only set it once");
+  HumongousThresholdBytes = HumongousThresholdWords * HeapWordSize;
+  assert (HumongousThresholdBytes <= RegionSizeBytes, "sanity");
+
+  // The rationale for trimming the TLAB sizes has to do with the raciness in
+  // TLAB allocation machinery. It may happen that TLAB sizing policy polls Shenandoah
+  // about next free size, gets the answer for region #N, goes away for a while, then
+  // tries to allocate in region #N, and fail because some other thread have claimed part
+  // of the region #N, and then the freeset allocation code has to retire the region #N,
+  // before moving the allocation to region #N+1.
+  //
+  // The worst case realizes when "answer" is "region size", which means it could
+  // prematurely retire an entire region. Having smaller TLABs does not fix that
+  // completely, but reduces the probability of too wasteful region retirement.
+  // With current divisor, we will waste no more than 1/8 of region size in the worst
+  // case. This also has a secondary effect on collection set selection: even under
+  // the race, the regions would be at least 7/8 used, which allows relying on
+  // "used" - "live" for cset selection. Otherwise, we can get the fragmented region
+  // below the garbage threshold that would never be considered for collection.
+  //
+  // The whole thing is mitigated if Elastic TLABs are enabled.
+  //
+  guarantee(MaxTLABSizeBytes == 0, "we should only set it once");
+  MaxTLABSizeBytes = MIN2(ShenandoahElasticTLAB ? RegionSizeBytes : (RegionSizeBytes / 8), HumongousThresholdBytes);
+  assert (MaxTLABSizeBytes > MinTLABSize, "should be larger");
+
+  guarantee(MaxTLABSizeWords == 0, "we should only set it once");
+  MaxTLABSizeWords = MaxTLABSizeBytes / HeapWordSize;
+
+  log_info(gc, init)("Regions: " SIZE_FORMAT " x " SIZE_FORMAT "%s",
+                     RegionCount, byte_size_in_proper_unit(RegionSizeBytes), proper_unit_for_byte_size(RegionSizeBytes));
+  log_info(gc, init)("Humongous object threshold: " SIZE_FORMAT "%s",
+                     byte_size_in_proper_unit(HumongousThresholdBytes), proper_unit_for_byte_size(HumongousThresholdBytes));
+  log_info(gc, init)("Max TLAB size: " SIZE_FORMAT "%s",
+                     byte_size_in_proper_unit(MaxTLABSizeBytes), proper_unit_for_byte_size(MaxTLABSizeBytes));
+}
+
+void ShenandoahHeapRegion::do_commit() {
+  if (!os::commit_memory((char *) _reserved.start(), _reserved.byte_size(), false)) {
+    report_java_out_of_memory("Unable to commit region");
+  }
+  if (!_heap->commit_bitmap_slice(this)) {
+    report_java_out_of_memory("Unable to commit bitmaps for region");
+  }
+  _heap->increase_committed(ShenandoahHeapRegion::region_size_bytes());
+}
+
+void ShenandoahHeapRegion::do_uncommit() {
+  if (!os::uncommit_memory((char *) _reserved.start(), _reserved.byte_size())) {
+    report_java_out_of_memory("Unable to uncommit region");
+  }
+  if (!_heap->uncommit_bitmap_slice(this)) {
+    report_java_out_of_memory("Unable to uncommit bitmaps for region");
+  }
+  _heap->decrease_committed(ShenandoahHeapRegion::region_size_bytes());
+}