/*

 * Copyright (c) 2001, 2012, 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 "gc_implementation/g1/heapRegion.hpp"

#include "gc_implementation/g1/heapRegionSeq.inline.hpp"

#include "gc_implementation/g1/heapRegionSets.hpp"

#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

#include "memory/allocation.hpp"

// Private

uint HeapRegionSeq::find_contiguous_from(uint from, uint num) {

  uint len = length();

  assert(num > 1, "use this only for sequences of length 2 or greater");

  assert(from <= len,

         err_msg("from: %u should be valid and <= than %u", from, len));

  uint curr = from;

  uint first = G1_NULL_HRS_INDEX;

  uint num_so_far = 0;

  while (curr < len && num_so_far < num) {

    if (at(curr)->is_empty()) {

      if (first == G1_NULL_HRS_INDEX) {

        first = curr;

        num_so_far = 1;

      } else {

        num_so_far += 1;

      }

    } else {

      first = G1_NULL_HRS_INDEX;

      num_so_far = 0;

    }

    curr += 1;

  }

  assert(num_so_far <= num, "post-condition");

  if (num_so_far == num) {

    // we found enough space for the humongous object

    assert(from <= first && first < len, "post-condition");

    assert(first < curr && (curr - first) == num, "post-condition");

    for (uint i = first; i < first + num; ++i) {

      assert(at(i)->is_empty(), "post-condition");

    }

    return first;

  } else {

    // we failed to find enough space for the humongous object

    return G1_NULL_HRS_INDEX;

  }

}

// Public

void HeapRegionSeq::initialize(HeapWord* bottom, HeapWord* end,

                               uint max_length) {

  assert((uintptr_t) bottom % HeapRegion::GrainBytes == 0,

         "bottom should be heap region aligned");

  assert((uintptr_t) end % HeapRegion::GrainBytes == 0,

         "end should be heap region aligned");

  _length = 0;

  _heap_bottom = bottom;

  _heap_end = end;

  _region_shift = HeapRegion::LogOfHRGrainBytes;

  _next_search_index = 0;

  _allocated_length = 0;

  _max_length = max_length;

  memset(_regions, 0, (size_t) max_length * sizeof(HeapRegion*));

  _regions_biased = _regions - ((uintx) bottom >> _region_shift);

  assert(&_regions[0] == &_regions_biased[addr_to_index_biased(bottom)],

         "bottom should be included in the region with index 0");

}

MemRegion HeapRegionSeq::expand_by(HeapWord* old_end,

                                   HeapWord* new_end,

                                   FreeRegionList* list) {

  assert(old_end < new_end, "don't call it otherwise");

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  HeapWord* next_bottom = old_end;

  assert(_heap_bottom <= next_bottom, "invariant");

  while (next_bottom < new_end) {

    assert(next_bottom < _heap_end, "invariant");

    uint index = length();

    assert(index < _max_length, "otherwise we cannot expand further");

    if (index == 0) {

      // We have not allocated any regions so far

      assert(next_bottom == _heap_bottom, "invariant");

    } else {

      // next_bottom should match the end of the last/previous region

      assert(next_bottom == at(index - 1)->end(), "invariant");

    }

    if (index == _allocated_length) {

      // We have to allocate a new HeapRegion.

      HeapRegion* new_hr = g1h->new_heap_region(index, next_bottom);

      if (new_hr == NULL) {

        // allocation failed, we bail out and return what we have done so far

        return MemRegion(old_end, next_bottom);

      }

      assert(_regions[index] == NULL, "invariant");

      _regions[index] = new_hr;

      increment_length(&_allocated_length);

    }

    // Have to increment the length first, otherwise we will get an

    // assert failure at(index) below.

    increment_length(&_length);

    HeapRegion* hr = at(index);

    list->add_as_tail(hr);

    next_bottom = hr->end();

  }

  assert(next_bottom == new_end, "post-condition");

  return MemRegion(old_end, next_bottom);

}

uint HeapRegionSeq::free_suffix() {

  uint res = 0;

  uint index = length();

  while (index > 0) {

    index -= 1;

    if (!at(index)->is_empty()) {

      break;

    }

    res += 1;

  }

  return res;

}

uint HeapRegionSeq::find_contiguous(uint num) {

  assert(num > 1, "use this only for sequences of length 2 or greater");

  assert(_next_search_index <= length(),

         err_msg("_next_search_index: %u should be valid and <= than %u",

                 _next_search_index, length()));

  uint start = _next_search_index;

  uint res = find_contiguous_from(start, num);

  if (res == G1_NULL_HRS_INDEX && start > 0) {

    // Try starting from the beginning. If _next_search_index was 0,

    // no point in doing this again.

    res = find_contiguous_from(0, num);

  }

  if (res != G1_NULL_HRS_INDEX) {

    assert(res < length(), err_msg("res: %u should be valid", res));

    _next_search_index = res + num;

    assert(_next_search_index <= length(),

           err_msg("_next_search_index: %u should be valid and <= than %u",

                   _next_search_index, length()));

  }

  return res;

}

void HeapRegionSeq::iterate(HeapRegionClosure* blk) const {

  iterate_from((HeapRegion*) NULL, blk);

}

void HeapRegionSeq::iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const {

  uint hr_index = 0;

  if (hr != NULL) {

    hr_index = hr->hrs_index();

  }

  uint len = length();

  for (uint i = hr_index; i < len; i += 1) {

    bool res = blk->doHeapRegion(at(i));

    if (res) {

      blk->incomplete();

      return;

    }

  }

  for (uint i = 0; i < hr_index; i += 1) {

    bool res = blk->doHeapRegion(at(i));

    if (res) {

      blk->incomplete();

      return;

    }

  }

}

MemRegion HeapRegionSeq::shrink_by(size_t shrink_bytes,

                                   uint* num_regions_deleted) {

  // Reset this in case it's currently pointing into the regions that

  // we just removed.

  _next_search_index = 0;

  assert(shrink_bytes % os::vm_page_size() == 0, "unaligned");

  assert(shrink_bytes % HeapRegion::GrainBytes == 0, "unaligned");

  assert(length() > 0, "the region sequence should not be empty");

  assert(length() <= _allocated_length, "invariant");

  assert(_allocated_length > 0, "we should have at least one region committed");

  // around the loop, i will be the next region to be removed

  uint i = length() - 1;

  assert(i > 0, "we should never remove all regions");

  // [last_start, end) is the MemRegion that covers the regions we will remove.

  HeapWord* end = at(i)->end();

  HeapWord* last_start = end;

  *num_regions_deleted = 0;

  while (shrink_bytes > 0) {

    HeapRegion* cur = at(i);

    // We should leave the humongous regions where they are.

    if (cur->isHumongous()) break;

    // We should stop shrinking if we come across a non-empty region.

    if (!cur->is_empty()) break;

    i -= 1;

    *num_regions_deleted += 1;

    shrink_bytes -= cur->capacity();

    last_start = cur->bottom();

    decrement_length(&_length);

    // We will reclaim the HeapRegion. _allocated_length should be

    // covering this index. So, even though we removed the region from

    // the active set by decreasing _length, we still have it

    // available in the future if we need to re-use it.

    assert(i > 0, "we should never remove all regions");

    assert(length() > 0, "we should never remove all regions");

  }

  return MemRegion(last_start, end);

}

#ifndef PRODUCT

void HeapRegionSeq::verify_optional() {

  guarantee(_length <= _allocated_length,

            err_msg("invariant: _length: %u _allocated_length: %u",

                    _length, _allocated_length));

  guarantee(_allocated_length <= _max_length,

            err_msg("invariant: _allocated_length: %u _max_length: %u",

                    _allocated_length, _max_length));

  guarantee(_next_search_index <= _length,

            err_msg("invariant: _next_search_index: %u _length: %u",

                    _next_search_index, _length));

  HeapWord* prev_end = _heap_bottom;

  for (uint i = 0; i < _allocated_length; i += 1) {

    HeapRegion* hr = _regions[i];

    guarantee(hr != NULL, err_msg("invariant: i: %u", i));

    guarantee(hr->bottom() == prev_end,

              err_msg("invariant i: %u "HR_FORMAT" prev_end: "PTR_FORMAT,

                      i, HR_FORMAT_PARAMS(hr), prev_end));

    guarantee(hr->hrs_index() == i,

              err_msg("invariant: i: %u hrs_index(): %u", i, hr->hrs_index()));

    if (i < _length) {

      // Asserts will fire if i is >= _length

      HeapWord* addr = hr->bottom();

      guarantee(addr_to_region(addr) == hr, "sanity");

      guarantee(addr_to_region_unsafe(addr) == hr, "sanity");

    } else {

      guarantee(hr->is_empty(), "sanity");

      guarantee(!hr->isHumongous(), "sanity");

      // using assert instead of guarantee here since containing_set()

      // is only available in non-product builds.

      assert(hr->containing_set() == NULL, "sanity");

    }

    if (hr->startsHumongous()) {

      prev_end = hr->orig_end();

    } else {

      prev_end = hr->end();

    }

  }

  for (uint i = _allocated_length; i < _max_length; i += 1) {

    guarantee(_regions[i] == NULL, err_msg("invariant i: %u", i));

  }

}

#endif // PRODUCT