mutableNUMASpace.cpp

/*
 * Copyright 2006-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 */

# include "incls/_precompiled.incl"
# include "incls/_mutableNUMASpace.cpp.incl"


MutableNUMASpace::MutableNUMASpace() {
  _lgrp_spaces = new (ResourceObj::C_HEAP) GrowableArray<LGRPSpace*>(0, true);
  _page_size = os::vm_page_size();
  _adaptation_cycles = 0;
  _samples_count = 0;
  update_layout(true);
}

MutableNUMASpace::~MutableNUMASpace() {
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    delete lgrp_spaces()->at(i);
  }
  delete lgrp_spaces();
}

void MutableNUMASpace::mangle_unused_area() {
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    LGRPSpace *ls = lgrp_spaces()->at(i);
    MutableSpace *s = ls->space();
    if (!os::numa_has_static_binding()) {
      HeapWord *top = MAX2((HeapWord*)round_down((intptr_t)s->top(), page_size()), s->bottom());
      if (top < s->end()) {
        ls->add_invalid_region(MemRegion(top, s->end()));
      }
    }
    s->mangle_unused_area();
  }
}

// There may be unallocated holes in the middle chunks
// that should be filled with dead objects to ensure parseability.
void MutableNUMASpace::ensure_parsability() {
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    LGRPSpace *ls = lgrp_spaces()->at(i);
    MutableSpace *s = ls->space();
    if (s->top() < top()) { // For all spaces preceeding the one containing top()
      if (s->free_in_words() > 0) {
        SharedHeap::fill_region_with_object(MemRegion(s->top(), s->end()));
        size_t area_touched_words = pointer_delta(s->end(), s->top());
#ifndef ASSERT
        if (!ZapUnusedHeapArea) {
          area_touched_words = MIN2((size_t)align_object_size(typeArrayOopDesc::header_size(T_INT)),
                                    area_touched_words);
        }
#endif
        if (!os::numa_has_static_binding()) {
          MemRegion invalid;
          HeapWord *crossing_start = (HeapWord*)round_to((intptr_t)s->top(), os::vm_page_size());
          HeapWord *crossing_end = (HeapWord*)round_to((intptr_t)(s->top() + area_touched_words),
                                                       os::vm_page_size());
          if (crossing_start != crossing_end) {
            // If object header crossed a small page boundary we mark the area
            // as invalid rounding it to a page_size().
            HeapWord *start = MAX2((HeapWord*)round_down((intptr_t)s->top(), page_size()), s->bottom());
            HeapWord *end = MIN2((HeapWord*)round_to((intptr_t)(s->top() + area_touched_words), page_size()),
                                 s->end());
            invalid = MemRegion(start, end);
          }

          ls->add_invalid_region(invalid);
        }
      }
    } else {
      if (!os::numa_has_static_binding()) {
#ifdef ASSERT
        MemRegion invalid(s->top(), s->end());
        ls->add_invalid_region(invalid);
#else
        if (ZapUnusedHeapArea) {
          MemRegion invalid(s->top(), s->end());
          ls->add_invalid_region(invalid);
        } else {
          return;
        }
#endif
      } else {
          return;
      }
    }
  }
}

size_t MutableNUMASpace::used_in_words() const {
  size_t s = 0;
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    s += lgrp_spaces()->at(i)->space()->used_in_words();
  }
  return s;
}

size_t MutableNUMASpace::free_in_words() const {
  size_t s = 0;
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    s += lgrp_spaces()->at(i)->space()->free_in_words();
  }
  return s;
}


size_t MutableNUMASpace::tlab_capacity(Thread *thr) const {
  guarantee(thr != NULL, "No thread");
  int lgrp_id = thr->lgrp_id();
  assert(lgrp_id != -1, "No lgrp_id set");
  int i = lgrp_spaces()->find(&lgrp_id, LGRPSpace::equals);
  if (i == -1) {
    return 0;
  }
  return lgrp_spaces()->at(i)->space()->capacity_in_bytes();
}

size_t MutableNUMASpace::unsafe_max_tlab_alloc(Thread *thr) const {
  guarantee(thr != NULL, "No thread");
  int lgrp_id = thr->lgrp_id();
  assert(lgrp_id != -1, "No lgrp_id set");
  int i = lgrp_spaces()->find(&lgrp_id, LGRPSpace::equals);
  if (i == -1) {
    return 0;
  }
  return lgrp_spaces()->at(i)->space()->free_in_bytes();
}

// Check if the NUMA topology has changed. Add and remove spaces if needed.
// The update can be forced by setting the force parameter equal to true.
bool MutableNUMASpace::update_layout(bool force) {
  // Check if the topology had changed.
  bool changed = os::numa_topology_changed();
  if (force || changed) {
    // Compute lgrp intersection. Add/remove spaces.
    int lgrp_limit = (int)os::numa_get_groups_num();
    int *lgrp_ids = NEW_C_HEAP_ARRAY(int, lgrp_limit);
    int lgrp_num = (int)os::numa_get_leaf_groups(lgrp_ids, lgrp_limit);
    assert(lgrp_num > 0, "There should be at least one locality group");
    // Add new spaces for the new nodes
    for (int i = 0; i < lgrp_num; i++) {
      bool found = false;
      for (int j = 0; j < lgrp_spaces()->length(); j++) {
        if (lgrp_spaces()->at(j)->lgrp_id() == lgrp_ids[i]) {
          found = true;
          break;
        }
      }
      if (!found) {
        lgrp_spaces()->append(new LGRPSpace(lgrp_ids[i]));
      }
    }

    // Remove spaces for the removed nodes.
    for (int i = 0; i < lgrp_spaces()->length();) {
      bool found = false;
      for (int j = 0; j < lgrp_num; j++) {
        if (lgrp_spaces()->at(i)->lgrp_id() == lgrp_ids[j]) {
          found = true;
          break;
        }
      }
      if (!found) {
        delete lgrp_spaces()->at(i);
        lgrp_spaces()->remove_at(i);
      } else {
        i++;
      }
    }

    FREE_C_HEAP_ARRAY(int, lgrp_ids);

    if (changed) {
      for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
        thread->set_lgrp_id(-1);
      }
    }
    return true;
  }
  return false;
}

// Bias region towards the first-touching lgrp. Set the right page sizes.
void MutableNUMASpace::bias_region(MemRegion mr, int lgrp_id) {
  HeapWord *start = (HeapWord*)round_to((intptr_t)mr.start(), page_size());
  HeapWord *end = (HeapWord*)round_down((intptr_t)mr.end(), page_size());
  if (end > start) {
    MemRegion aligned_region(start, end);
    assert((intptr_t)aligned_region.start()     % page_size() == 0 &&
           (intptr_t)aligned_region.byte_size() % page_size() == 0, "Bad alignment");
    assert(region().contains(aligned_region), "Sanity");
    // First we tell the OS which page size we want in the given range. The underlying
    // large page can be broken down if we require small pages.
    os::realign_memory((char*)aligned_region.start(), aligned_region.byte_size(), page_size());
    // Then we uncommit the pages in the range.
    os::free_memory((char*)aligned_region.start(), aligned_region.byte_size());
    // And make them local/first-touch biased.
    os::numa_make_local((char*)aligned_region.start(), aligned_region.byte_size(), lgrp_id);
  }
}

// Free all pages in the region.
void MutableNUMASpace::free_region(MemRegion mr) {
  HeapWord *start = (HeapWord*)round_to((intptr_t)mr.start(), page_size());
  HeapWord *end = (HeapWord*)round_down((intptr_t)mr.end(), page_size());
  if (end > start) {
    MemRegion aligned_region(start, end);
    assert((intptr_t)aligned_region.start()     % page_size() == 0 &&
           (intptr_t)aligned_region.byte_size() % page_size() == 0, "Bad alignment");
    assert(region().contains(aligned_region), "Sanity");
    os::free_memory((char*)aligned_region.start(), aligned_region.byte_size());
  }
}

// Update space layout. Perform adaptation.
void MutableNUMASpace::update() {
  if (update_layout(false)) {
    // If the topology has changed, make all chunks zero-sized.
    for (int i = 0; i < lgrp_spaces()->length(); i++) {
      MutableSpace *s = lgrp_spaces()->at(i)->space();
      s->set_end(s->bottom());
      s->set_top(s->bottom());
    }
    initialize(region(), true);
  } else {
    bool should_initialize = false;
    if (!os::numa_has_static_binding()) {
      for (int i = 0; i < lgrp_spaces()->length(); i++) {
        if (!lgrp_spaces()->at(i)->invalid_region().is_empty()) {
          should_initialize = true;
          break;
        }
      }
    }

    if (should_initialize ||
        (UseAdaptiveNUMAChunkSizing && adaptation_cycles() < samples_count())) {
      initialize(region(), true);
    }
  }

  if (NUMAStats) {
    for (int i = 0; i < lgrp_spaces()->length(); i++) {
      lgrp_spaces()->at(i)->accumulate_statistics(page_size());
    }
  }

  scan_pages(NUMAPageScanRate);
}

// Scan pages. Free pages that have smaller size or wrong placement.
void MutableNUMASpace::scan_pages(size_t page_count)
{
  size_t pages_per_chunk = page_count / lgrp_spaces()->length();
  if (pages_per_chunk > 0) {
    for (int i = 0; i < lgrp_spaces()->length(); i++) {
      LGRPSpace *ls = lgrp_spaces()->at(i);
      ls->scan_pages(page_size(), pages_per_chunk);
    }
  }
}

// Accumulate statistics about the allocation rate of each lgrp.
void MutableNUMASpace::accumulate_statistics() {
  if (UseAdaptiveNUMAChunkSizing) {
    for (int i = 0; i < lgrp_spaces()->length(); i++) {
      lgrp_spaces()->at(i)->sample();
    }
    increment_samples_count();
  }

  if (NUMAStats) {
    for (int i = 0; i < lgrp_spaces()->length(); i++) {
      lgrp_spaces()->at(i)->accumulate_statistics(page_size());
    }
  }
}

// Get the current size of a chunk.
// This function computes the size of the chunk based on the
// difference between chunk ends. This allows it to work correctly in
// case the whole space is resized and during the process of adaptive
// chunk resizing.
size_t MutableNUMASpace::current_chunk_size(int i) {
  HeapWord *cur_end, *prev_end;
  if (i == 0) {
    prev_end = bottom();
  } else {
    prev_end = lgrp_spaces()->at(i - 1)->space()->end();
  }
  if (i == lgrp_spaces()->length() - 1) {
    cur_end = end();
  } else {
    cur_end = lgrp_spaces()->at(i)->space()->end();
  }
  if (cur_end > prev_end) {
    return pointer_delta(cur_end, prev_end, sizeof(char));
  }
  return 0;
}

// Return the default chunk size by equally diving the space.
// page_size() aligned.
size_t MutableNUMASpace::default_chunk_size() {
  return base_space_size() / lgrp_spaces()->length() * page_size();
}

// Produce a new chunk size. page_size() aligned.
size_t MutableNUMASpace::adaptive_chunk_size(int i, size_t limit) {
  size_t pages_available = base_space_size();
  for (int j = 0; j < i; j++) {
    pages_available -= round_down(current_chunk_size(j), page_size()) / page_size();
  }
  pages_available -= lgrp_spaces()->length() - i - 1;
  assert(pages_available > 0, "No pages left");
  float alloc_rate = 0;
  for (int j = i; j < lgrp_spaces()->length(); j++) {
    alloc_rate += lgrp_spaces()->at(j)->alloc_rate()->average();
  }
  size_t chunk_size = 0;
  if (alloc_rate > 0) {
    LGRPSpace *ls = lgrp_spaces()->at(i);
    chunk_size = (size_t)(ls->alloc_rate()->average() * pages_available / alloc_rate) * page_size();
  }
  chunk_size = MAX2(chunk_size, page_size());

  if (limit > 0) {
    limit = round_down(limit, page_size());
    if (chunk_size > current_chunk_size(i)) {
      chunk_size = MIN2((off_t)chunk_size, (off_t)current_chunk_size(i) + (off_t)limit);
    } else {
      chunk_size = MAX2((off_t)chunk_size, (off_t)current_chunk_size(i) - (off_t)limit);
    }
  }
  assert(chunk_size <= pages_available * page_size(), "Chunk size out of range");
  return chunk_size;
}


// Return the bottom_region and the top_region. Align them to page_size() boundary.
// |------------------new_region---------------------------------|
// |----bottom_region--|---intersection---|------top_region------|
void MutableNUMASpace::select_tails(MemRegion new_region, MemRegion intersection,
                                    MemRegion* bottom_region, MemRegion *top_region) {
  // Is there bottom?
  if (new_region.start() < intersection.start()) { // Yes
    // Try to coalesce small pages into a large one.
    if (UseLargePages && page_size() >= os::large_page_size()) {
      HeapWord* p = (HeapWord*)round_to((intptr_t) intersection.start(), os::large_page_size());
      if (new_region.contains(p)
          && pointer_delta(p, new_region.start(), sizeof(char)) >= os::large_page_size()) {
        if (intersection.contains(p)) {
          intersection = MemRegion(p, intersection.end());
        } else {
          intersection = MemRegion(p, p);
        }
      }
    }
    *bottom_region = MemRegion(new_region.start(), intersection.start());
  } else {
    *bottom_region = MemRegion();
  }

  // Is there top?
  if (intersection.end() < new_region.end()) { // Yes
    // Try to coalesce small pages into a large one.
    if (UseLargePages && page_size() >= os::large_page_size()) {
      HeapWord* p = (HeapWord*)round_down((intptr_t) intersection.end(), os::large_page_size());
      if (new_region.contains(p)
          && pointer_delta(new_region.end(), p, sizeof(char)) >= os::large_page_size()) {
        if (intersection.contains(p)) {
          intersection = MemRegion(intersection.start(), p);
        } else {
          intersection = MemRegion(p, p);
        }
      }
    }
    *top_region = MemRegion(intersection.end(), new_region.end());
  } else {
    *top_region = MemRegion();
  }
}

// Try to merge the invalid region with the bottom or top region by decreasing
// the intersection area. Return the invalid_region aligned to the page_size()
// boundary if it's inside the intersection. Return non-empty invalid_region
// if it lies inside the intersection (also page-aligned).
// |------------------new_region---------------------------------|
// |----------------|-------invalid---|--------------------------|
// |----bottom_region--|---intersection---|------top_region------|
void MutableNUMASpace::merge_regions(MemRegion new_region, MemRegion* intersection,
                                     MemRegion *invalid_region) {
  if (intersection->start() >= invalid_region->start() && intersection->contains(invalid_region->end())) {
    *intersection = MemRegion(invalid_region->end(), intersection->end());
    *invalid_region = MemRegion();
  } else
    if (intersection->end() <= invalid_region->end() && intersection->contains(invalid_region->start())) {
      *intersection = MemRegion(intersection->start(), invalid_region->start());
      *invalid_region = MemRegion();
    } else
      if (intersection->equals(*invalid_region) || invalid_region->contains(*intersection)) {
        *intersection = MemRegion(new_region.start(), new_region.start());
        *invalid_region = MemRegion();
      } else
        if (intersection->contains(invalid_region)) {
            // That's the only case we have to make an additional bias_region() call.
            HeapWord* start = invalid_region->start();
            HeapWord* end = invalid_region->end();
            if (UseLargePages && page_size() >= os::large_page_size()) {
              HeapWord *p = (HeapWord*)round_down((intptr_t) start, os::large_page_size());
              if (new_region.contains(p)) {
                start = p;
              }
              p = (HeapWord*)round_to((intptr_t) end, os::large_page_size());
              if (new_region.contains(end)) {
                end = p;
              }
            }
            if (intersection->start() > start) {
              *intersection = MemRegion(start, intersection->end());
            }
            if (intersection->end() < end) {
              *intersection = MemRegion(intersection->start(), end);
            }
            *invalid_region = MemRegion(start, end);
        }
}

void MutableNUMASpace::initialize(MemRegion mr, bool clear_space) {
  assert(clear_space, "Reallocation will destory data!");
  assert(lgrp_spaces()->length() > 0, "There should be at least one space");

  MemRegion old_region = region(), new_region;
  set_bottom(mr.start());
  set_end(mr.end());
  MutableSpace::set_top(bottom());

  // Compute chunk sizes
  size_t prev_page_size = page_size();
  set_page_size(UseLargePages ? os::large_page_size() : os::vm_page_size());
  HeapWord* rounded_bottom = (HeapWord*)round_to((intptr_t) bottom(), page_size());
  HeapWord* rounded_end = (HeapWord*)round_down((intptr_t) end(), page_size());
  size_t base_space_size_pages = pointer_delta(rounded_end, rounded_bottom, sizeof(char)) / page_size();

  // Try small pages if the chunk size is too small
  if (base_space_size_pages / lgrp_spaces()->length() == 0
      && page_size() > (size_t)os::vm_page_size()) {
    set_page_size(os::vm_page_size());
    rounded_bottom = (HeapWord*)round_to((intptr_t) bottom(), page_size());
    rounded_end = (HeapWord*)round_down((intptr_t) end(), page_size());
    base_space_size_pages = pointer_delta(rounded_end, rounded_bottom, sizeof(char)) / page_size();
  }
  guarantee(base_space_size_pages / lgrp_spaces()->length() > 0, "Space too small");
  set_base_space_size(base_space_size_pages);

  // Handle space resize
  MemRegion top_region, bottom_region;
  if (!old_region.equals(region())) {
    new_region = MemRegion(rounded_bottom, rounded_end);
    MemRegion intersection = new_region.intersection(old_region);
    if (intersection.start() == NULL ||
        intersection.end() == NULL   ||
        prev_page_size > page_size()) { // If the page size got smaller we have to change
                                        // the page size preference for the whole space.
      intersection = MemRegion(new_region.start(), new_region.start());
    }
    select_tails(new_region, intersection, &bottom_region, &top_region);
    bias_region(bottom_region, lgrp_spaces()->at(0)->lgrp_id());
    bias_region(top_region, lgrp_spaces()->at(lgrp_spaces()->length() - 1)->lgrp_id());
  }

  // Check if the space layout has changed significantly?
  // This happens when the space has been resized so that either head or tail
  // chunk became less than a page.
  bool layout_valid = UseAdaptiveNUMAChunkSizing          &&
                      current_chunk_size(0) > page_size() &&
                      current_chunk_size(lgrp_spaces()->length() - 1) > page_size();


  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    LGRPSpace *ls = lgrp_spaces()->at(i);
    MutableSpace *s = ls->space();
    old_region = s->region();

    size_t chunk_byte_size = 0, old_chunk_byte_size = 0;
    if (i < lgrp_spaces()->length() - 1) {
      if (!UseAdaptiveNUMAChunkSizing                                ||
          (UseAdaptiveNUMAChunkSizing && NUMAChunkResizeWeight == 0) ||
           samples_count() < AdaptiveSizePolicyReadyThreshold) {
        // No adaptation. Divide the space equally.
        chunk_byte_size = default_chunk_size();
      } else
        if (!layout_valid || NUMASpaceResizeRate == 0) {
          // Fast adaptation. If no space resize rate is set, resize
          // the chunks instantly.
          chunk_byte_size = adaptive_chunk_size(i, 0);
        } else {
          // Slow adaptation. Resize the chunks moving no more than
          // NUMASpaceResizeRate bytes per collection.
          size_t limit = NUMASpaceResizeRate /
                         (lgrp_spaces()->length() * (lgrp_spaces()->length() + 1) / 2);
          chunk_byte_size = adaptive_chunk_size(i, MAX2(limit * (i + 1), page_size()));
        }

      assert(chunk_byte_size >= page_size(), "Chunk size too small");
      assert(chunk_byte_size <= capacity_in_bytes(), "Sanity check");
    }

    if (i == 0) { // Bottom chunk
      if (i != lgrp_spaces()->length() - 1) {
        new_region = MemRegion(bottom(), rounded_bottom + (chunk_byte_size >> LogHeapWordSize));
      } else {
        new_region = MemRegion(bottom(), end());
      }
    } else
      if (i < lgrp_spaces()->length() - 1) { // Middle chunks
        MutableSpace *ps = lgrp_spaces()->at(i - 1)->space();
        new_region = MemRegion(ps->end(),
                               ps->end() + (chunk_byte_size >> LogHeapWordSize));
      } else { // Top chunk
        MutableSpace *ps = lgrp_spaces()->at(i - 1)->space();
        new_region = MemRegion(ps->end(), end());
      }
    guarantee(region().contains(new_region), "Region invariant");


    // The general case:
    // |---------------------|--invalid---|--------------------------|
    // |------------------new_region---------------------------------|
    // |----bottom_region--|---intersection---|------top_region------|
    //                     |----old_region----|
    // The intersection part has all pages in place we don't need to migrate them.
    // Pages for the top and bottom part should be freed and then reallocated.

    MemRegion intersection = old_region.intersection(new_region);

    if (intersection.start() == NULL || intersection.end() == NULL) {
      intersection = MemRegion(new_region.start(), new_region.start());
    }

    if (!os::numa_has_static_binding()) {
      MemRegion invalid_region = ls->invalid_region().intersection(new_region);
      // Invalid region is a range of memory that could've possibly
      // been allocated on the other node. That's relevant only on Solaris where
      // there is no static memory binding.
      if (!invalid_region.is_empty()) {
        merge_regions(new_region, &intersection, &invalid_region);
        free_region(invalid_region);
        ls->set_invalid_region(MemRegion());
      }
    }

    select_tails(new_region, intersection, &bottom_region, &top_region);

    if (!os::numa_has_static_binding()) {
      // If that's a system with the first-touch policy then it's enough
      // to free the pages.
      free_region(bottom_region);
      free_region(top_region);
    } else {
      // In a system with static binding we have to change the bias whenever
      // we reshape the heap.
      bias_region(bottom_region, ls->lgrp_id());
      bias_region(top_region, ls->lgrp_id());
    }

    // If we clear the region, we would mangle it in debug. That would cause page
    // allocation in a different place. Hence setting the top directly.
    s->initialize(new_region, false);
    s->set_top(s->bottom());

    set_adaptation_cycles(samples_count());
  }
}

// Set the top of the whole space.
// Mark the the holes in chunks below the top() as invalid.
void MutableNUMASpace::set_top(HeapWord* value) {
  bool found_top = false;
  for (int i = 0; i < lgrp_spaces()->length();) {
    LGRPSpace *ls = lgrp_spaces()->at(i);
    MutableSpace *s = ls->space();
    HeapWord *top = MAX2((HeapWord*)round_down((intptr_t)s->top(), page_size()), s->bottom());

    if (s->contains(value)) {
      // Check if setting the chunk's top to a given value would create a hole less than
      // a minimal object; assuming that's not the last chunk in which case we don't care.
      if (i < lgrp_spaces()->length() - 1) {
        size_t remainder = pointer_delta(s->end(), value);
        const size_t minimal_object_size = oopDesc::header_size();
        if (remainder < minimal_object_size && remainder > 0) {
          // Add a filler object of a minimal size, it will cross the chunk boundary.
          SharedHeap::fill_region_with_object(MemRegion(value, minimal_object_size));
          value += minimal_object_size;
          assert(!s->contains(value), "Should be in the next chunk");
          // Restart the loop from the same chunk, since the value has moved
          // to the next one.
          continue;
        }
      }

      if (!os::numa_has_static_binding() && top < value && top < s->end()) {
        ls->add_invalid_region(MemRegion(top, value));
      }
      s->set_top(value);
      found_top = true;
    } else {
        if (found_top) {
            s->set_top(s->bottom());
        } else {
          if (!os::numa_has_static_binding() && top < s->end()) {
            ls->add_invalid_region(MemRegion(top, s->end()));
          }
          s->set_top(s->end());
        }
    }
    i++;
  }
  MutableSpace::set_top(value);
}

void MutableNUMASpace::clear() {
  MutableSpace::set_top(bottom());
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    lgrp_spaces()->at(i)->space()->clear();
  }
}

/*
   Linux supports static memory binding, therefore the most part of the
   logic dealing with the possible invalid page allocation is effectively
   disabled. Besides there is no notion of the home node in Linux. A
   thread is allowed to migrate freely. Although the scheduler is rather
   reluctant to move threads between the nodes. We check for the current
   node every allocation. And with a high probability a thread stays on
   the same node for some time allowing local access to recently allocated
   objects.
 */

HeapWord* MutableNUMASpace::allocate(size_t size) {
  Thread* thr = Thread::current();
  int lgrp_id = thr->lgrp_id();
  if (lgrp_id == -1 || !os::numa_has_group_homing()) {
    lgrp_id = os::numa_get_group_id();
    thr->set_lgrp_id(lgrp_id);
  }

  int i = lgrp_spaces()->find(&lgrp_id, LGRPSpace::equals);

  // It is possible that a new CPU has been hotplugged and
  // we haven't reshaped the space accordingly.
  if (i == -1) {
    i = os::random() % lgrp_spaces()->length();
  }

  MutableSpace *s = lgrp_spaces()->at(i)->space();
  HeapWord *p = s->allocate(size);

  if (p != NULL) {
    size_t remainder = s->free_in_words();
    if (remainder < (size_t)oopDesc::header_size() && remainder > 0) {
      s->set_top(s->top() - size);
      p = NULL;
    }
  }
  if (p != NULL) {
    if (top() < s->top()) { // Keep _top updated.
      MutableSpace::set_top(s->top());
    }
  }
  // Make the page allocation happen here if there is no static binding..
  if (p != NULL && !os::numa_has_static_binding()) {
    for (HeapWord *i = p; i < p + size; i += os::vm_page_size() >> LogHeapWordSize) {
      *(int*)i = 0;
    }
  }
  return p;
}

// This version is lock-free.
HeapWord* MutableNUMASpace::cas_allocate(size_t size) {
  Thread* thr = Thread::current();
  int lgrp_id = thr->lgrp_id();
  if (lgrp_id == -1 || !os::numa_has_group_homing()) {
    lgrp_id = os::numa_get_group_id();
    thr->set_lgrp_id(lgrp_id);
  }

  int i = lgrp_spaces()->find(&lgrp_id, LGRPSpace::equals);
  // It is possible that a new CPU has been hotplugged and
  // we haven't reshaped the space accordingly.
  if (i == -1) {
    i = os::random() % lgrp_spaces()->length();
  }
  MutableSpace *s = lgrp_spaces()->at(i)->space();
  HeapWord *p = s->cas_allocate(size);
  if (p != NULL) {
    size_t remainder = pointer_delta(s->end(), p + size);
    if (remainder < (size_t)oopDesc::header_size() && remainder > 0) {
      if (s->cas_deallocate(p, size)) {
        // We were the last to allocate and created a fragment less than
        // a minimal object.
        p = NULL;
      } else {
        guarantee(false, "Deallocation should always succeed");
      }
    }
  }
  if (p != NULL) {
    HeapWord* cur_top, *cur_chunk_top = p + size;
    while ((cur_top = top()) < cur_chunk_top) { // Keep _top updated.
      if (Atomic::cmpxchg_ptr(cur_chunk_top, top_addr(), cur_top) == cur_top) {
        break;
      }
    }
  }

  // Make the page allocation happen here if there is no static binding.
  if (p != NULL && !os::numa_has_static_binding() ) {
    for (HeapWord *i = p; i < p + size; i += os::vm_page_size() >> LogHeapWordSize) {
      *(int*)i = 0;
    }
  }
  return p;
}

void MutableNUMASpace::print_short_on(outputStream* st) const {
  MutableSpace::print_short_on(st);
  st->print(" (");
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    st->print("lgrp %d: ", lgrp_spaces()->at(i)->lgrp_id());
    lgrp_spaces()->at(i)->space()->print_short_on(st);
    if (i < lgrp_spaces()->length() - 1) {
      st->print(", ");
    }
  }
  st->print(")");
}

void MutableNUMASpace::print_on(outputStream* st) const {
  MutableSpace::print_on(st);
  for (int i = 0; i < lgrp_spaces()->length(); i++) {
    LGRPSpace *ls = lgrp_spaces()->at(i);
    st->print("    lgrp %d", ls->lgrp_id());
    ls->space()->print_on(st);
    if (NUMAStats) {
      for (int i = 0; i < lgrp_spaces()->length(); i++) {
        lgrp_spaces()->at(i)->accumulate_statistics(page_size());
      }
      st->print("    local/remote/unbiased/uncommitted: %dK/%dK/%dK/%dK, large/small pages: %d/%d\n",
                ls->space_stats()->_local_space / K,
                ls->space_stats()->_remote_space / K,
                ls->space_stats()->_unbiased_space / K,
                ls->space_stats()->_uncommited_space / K,
                ls->space_stats()->_large_pages,
                ls->space_stats()->_small_pages);
    }
  }
}

void MutableNUMASpace::verify(bool allow_dirty) {
  // This can be called after setting an arbitary value to the space's top,
  // so an object can cross the chunk boundary. We ensure the parsablity
  // of the space and just walk the objects in linear fashion.
  ensure_parsability();
  MutableSpace::verify(allow_dirty);
}

// Scan pages and gather stats about page placement and size.
void MutableNUMASpace::LGRPSpace::accumulate_statistics(size_t page_size) {
  clear_space_stats();
  char *start = (char*)round_to((intptr_t) space()->bottom(), page_size);
  char* end = (char*)round_down((intptr_t) space()->end(), page_size);
  if (start < end) {
    for (char *p = start; p < end;) {
      os::page_info info;
      if (os::get_page_info(p, &info)) {
        if (info.size > 0) {
          if (info.size > (size_t)os::vm_page_size()) {
            space_stats()->_large_pages++;
          } else {
            space_stats()->_small_pages++;
          }
          if (info.lgrp_id == lgrp_id()) {
            space_stats()->_local_space += info.size;
          } else {
            space_stats()->_remote_space += info.size;
          }
          p += info.size;
        } else {
          p += os::vm_page_size();
          space_stats()->_uncommited_space += os::vm_page_size();
        }
      } else {
        return;
      }
    }
  }
  space_stats()->_unbiased_space = pointer_delta(start, space()->bottom(), sizeof(char)) +
                                   pointer_delta(space()->end(), end, sizeof(char));

}

// Scan page_count pages and verify if they have the right size and right placement.
// If invalid pages are found they are freed in hope that subsequent reallocation
// will be more successful.
void MutableNUMASpace::LGRPSpace::scan_pages(size_t page_size, size_t page_count)
{
  char* range_start = (char*)round_to((intptr_t) space()->bottom(), page_size);
  char* range_end = (char*)round_down((intptr_t) space()->end(), page_size);

  if (range_start > last_page_scanned() || last_page_scanned() >= range_end) {
    set_last_page_scanned(range_start);
  }

  char *scan_start = last_page_scanned();
  char* scan_end = MIN2(scan_start + page_size * page_count, range_end);

  os::page_info page_expected, page_found;
  page_expected.size = page_size;
  page_expected.lgrp_id = lgrp_id();

  char *s = scan_start;
  while (s < scan_end) {
    char *e = os::scan_pages(s, (char*)scan_end, &page_expected, &page_found);
    if (e == NULL) {
      break;
    }
    if (e != scan_end) {
      if ((page_expected.size != page_size || page_expected.lgrp_id != lgrp_id())
          && page_expected.size != 0) {
        os::free_memory(s, pointer_delta(e, s, sizeof(char)));
      }
      page_expected = page_found;
    }
    s = e;
  }

  set_last_page_scanned(scan_end);
}