/*

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 * 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

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 */

#include "precompiled.hpp"

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

#include "gc_implementation/g1/heapRegionSeq.hpp"

#include "memory/allocation.hpp"

// Local to this file.

static int orderRegions(HeapRegion** hr1p, HeapRegion** hr2p) {

  if ((*hr1p)->end() <= (*hr2p)->bottom()) return -1;

  else if ((*hr2p)->end() <= (*hr1p)->bottom()) return 1;

  else if (*hr1p == *hr2p) return 0;

  else {

    assert(false, "We should never compare distinct overlapping regions.");

  }

  return 0;

}

HeapRegionSeq::HeapRegionSeq(const size_t max_size) :

  _alloc_search_start(0),

  // The line below is the worst bit of C++ hackery I've ever written

  // (Detlefs, 11/23).  You should think of it as equivalent to

  // "_regions(100, true)": initialize the growable array and inform it

  // that it should allocate its elem array(s) on the C heap.

  //

  // The first argument, however, is actually a comma expression

  // (set_allocation_type(this, C_HEAP), 100). The purpose of the

  // set_allocation_type() call is to replace the default allocation

  // type for embedded objects STACK_OR_EMBEDDED with C_HEAP. It will

  // allow to pass the assert in GenericGrowableArray() which checks

  // that a growable array object must be on C heap if elements are.

  //

  // Note: containing object is allocated on C heap since it is CHeapObj.

  //

  _regions((ResourceObj::set_allocation_type((address)&_regions,

                                             ResourceObj::C_HEAP),

            (int)max_size),

           true),

  _next_rr_candidate(0),

  _seq_bottom(NULL)

{}

// Private methods.

HeapWord*

HeapRegionSeq::alloc_obj_from_region_index(int ind, size_t word_size) {

  assert(G1CollectedHeap::isHumongous(word_size),

         "Allocation size should be humongous");

  int cur = ind;

  int first = cur;

  size_t sumSizes = 0;

  while (cur < _regions.length() && sumSizes < word_size) {

    // Loop invariant:

    //  For all i in [first, cur):

    //       _regions.at(i)->is_empty()

    //    && _regions.at(i) is contiguous with its predecessor, if any

    //  && sumSizes is the sum of the sizes of the regions in the interval

    //       [first, cur)

    HeapRegion* curhr = _regions.at(cur);

    if (curhr->is_empty()

        && (first == cur

            || (_regions.at(cur-1)->end() ==

                curhr->bottom()))) {

      sumSizes += curhr->capacity() / HeapWordSize;

    } else {

      first = cur + 1;

      sumSizes = 0;

    }

    cur++;

  }

  if (sumSizes >= word_size) {

    _alloc_search_start = cur;

    // We need to initialize the region(s) we just discovered. This is

    // a bit tricky given that it can happen concurrently with

    // refinement threads refining cards on these regions and

    // potentially wanting to refine the BOT as they are scanning

    // those cards (this can happen shortly after a cleanup; see CR

    // 6991377). So we have to set up the region(s) carefully and in

    // a specific order.

    // Currently, allocs_are_zero_filled() returns false. The zero

    // filling infrastructure will be going away soon (see CR 6977804).

    // So no need to do anything else here.

    bool zf = G1CollectedHeap::heap()->allocs_are_zero_filled();

    assert(!zf, "not supported");

    // This will be the "starts humongous" region.

    HeapRegion* first_hr = _regions.at(first);

    {

      MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);

      first_hr->set_zero_fill_allocated();

    }

    // The header of the new object will be placed at the bottom of

    // the first region.

    HeapWord* new_obj = first_hr->bottom();

    // This will be the new end of the first region in the series that

    // should also match the end of the last region in the seriers.

    // (Note: sumSizes = "region size" x "number of regions we found").

    HeapWord* new_end = new_obj + sumSizes;

    // This will be the new top of the first region that will reflect

    // this allocation.

    HeapWord* new_top = new_obj + word_size;

    // First, we need to zero the header of the space that we will be

    // allocating. When we update top further down, some refinement

    // threads might try to scan the region. By zeroing the header we

    // ensure that any thread that will try to scan the region will

    // come across the zero klass word and bail out.

    //

    // NOTE: It would not have been correct to have used

    // CollectedHeap::fill_with_object() and make the space look like

    // an int array. The thread that is doing the allocation will

    // later update the object header to a potentially different array

    // type and, for a very short period of time, the klass and length

    // fields will be inconsistent. This could cause a refinement

    // thread to calculate the object size incorrectly.

    Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);

    // We will set up the first region as "starts humongous". This

    // will also update the BOT covering all the regions to reflect

    // that there is a single object that starts at the bottom of the

    // first region.

    first_hr->set_startsHumongous(new_end);

    // Then, if there are any, we will set up the "continues

    // humongous" regions.

    HeapRegion* hr = NULL;

    for (int i = first + 1; i < cur; ++i) {

      hr = _regions.at(i);

      {

        MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);

        hr->set_zero_fill_allocated();

      }

      hr->set_continuesHumongous(first_hr);

    }

    // If we have "continues humongous" regions (hr != NULL), then the

    // end of the last one should match new_end.

    assert(hr == NULL || hr->end() == new_end, "sanity");

    // Up to this point no concurrent thread would have been able to

    // do any scanning on any region in this series. All the top

    // fields still point to bottom, so the intersection between

    // [bottom,top] and [card_start,card_end] will be empty. Before we

    // update the top fields, we'll do a storestore to make sure that

    // no thread sees the update to top before the zeroing of the

    // object header and the BOT initialization.

    OrderAccess::storestore();

    // Now that the BOT and the object header have been initialized,

    // we can update top of the "starts humongous" region.

    assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),

           "new_top should be in this region");

    first_hr->set_top(new_top);

    // Now, we will update the top fields of the "continues humongous"

    // regions. The reason we need to do this is that, otherwise,

    // these regions would look empty and this will confuse parts of

    // G1. For example, the code that looks for a consecutive number

    // of empty regions will consider them empty and try to

    // re-allocate them. We can extend is_empty() to also include

    // !continuesHumongous(), but it is easier to just update the top

    // fields here.

    hr = NULL;

    for (int i = first + 1; i < cur; ++i) {

      hr = _regions.at(i);

      if ((i + 1) == cur) {

        // last continues humongous region

        assert(hr->bottom() < new_top && new_top <= hr->end(),

               "new_top should fall on this region");

        hr->set_top(new_top);

      } else {

        // not last one

        assert(new_top > hr->end(), "new_top should be above this region");

        hr->set_top(hr->end());

      }

    }

    // If we have continues humongous regions (hr != NULL), then the

    // end of the last one should match new_end and its top should

    // match new_top.

    assert(hr == NULL ||

           (hr->end() == new_end && hr->top() == new_top), "sanity");

    return new_obj;

  } else {

    // If we started from the beginning, we want to know why we can't alloc.

    return NULL;

  }

}

void HeapRegionSeq::print_empty_runs() {

  int empty_run = 0;

  int n_empty = 0;

  int empty_run_start;

  for (int i = 0; i < _regions.length(); i++) {

    HeapRegion* r = _regions.at(i);

    if (r->continuesHumongous()) continue;

    if (r->is_empty()) {

      assert(!r->isHumongous(), "H regions should not be empty.");

      if (empty_run == 0) empty_run_start = i;

      empty_run++;

      n_empty++;

    } else {

      if (empty_run > 0) {

        gclog_or_tty->print("  %d:%d", empty_run_start, empty_run);

        empty_run = 0;

      }

    }

  }

  if (empty_run > 0) {

    gclog_or_tty->print(" %d:%d", empty_run_start, empty_run);

  }

  gclog_or_tty->print_cr(" [tot = %d]", n_empty);

}

int HeapRegionSeq::find(HeapRegion* hr) {

  // FIXME: optimized for adjacent regions of fixed size.

  int ind = hr->hrs_index();

  if (ind != -1) {

    assert(_regions.at(ind) == hr, "Mismatch");

  }

  return ind;

}

// Public methods.

void HeapRegionSeq::insert(HeapRegion* hr) {

  assert(!_regions.is_full(), "Too many elements in HeapRegionSeq");

  if (_regions.length() == 0

      || _regions.top()->end() <= hr->bottom()) {

    hr->set_hrs_index(_regions.length());

    _regions.append(hr);

  } else {

    _regions.append(hr);

    _regions.sort(orderRegions);

    for (int i = 0; i < _regions.length(); i++) {

      _regions.at(i)->set_hrs_index(i);

    }

  }

  char* bot = (char*)_regions.at(0)->bottom();

  if (_seq_bottom == NULL || bot < _seq_bottom) _seq_bottom = bot;

}

size_t HeapRegionSeq::length() {

  return _regions.length();

}

size_t HeapRegionSeq::free_suffix() {

  size_t res = 0;

  int first = _regions.length() - 1;

  int cur = first;

  while (cur >= 0 &&

         (_regions.at(cur)->is_empty()

          && (first == cur

              || (_regions.at(cur+1)->bottom() ==

                  _regions.at(cur)->end())))) {

      res++;

      cur--;

  }

  return res;

}

HeapWord* HeapRegionSeq::obj_allocate(size_t word_size) {

  int cur = _alloc_search_start;

  // Make sure "cur" is a valid index.

  assert(cur >= 0, "Invariant.");

  HeapWord* res = alloc_obj_from_region_index(cur, word_size);

  if (res == NULL)

    res = alloc_obj_from_region_index(0, word_size);

  return res;

}

void HeapRegionSeq::iterate(HeapRegionClosure* blk) {

  iterate_from((HeapRegion*)NULL, blk);

}

// The first argument r is the heap region at which iteration begins.

// This operation runs fastest when r is NULL, or the heap region for

// which a HeapRegionClosure most recently returned true, or the

// heap region immediately to its right in the sequence.  In all

// other cases a linear search is required to find the index of r.

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

  // :::: FIXME ::::

  // Static cache value is bad, especially when we start doing parallel

  // remembered set update. For now just don't cache anything (the

  // code in the def'd out blocks).

#if 0

  static int cached_j = 0;

#endif

  int len = _regions.length();

  int j = 0;

  // Find the index of r.

  if (r != NULL) {

#if 0

    assert(cached_j >= 0, "Invariant.");

    if ((cached_j < len) && (r == _regions.at(cached_j))) {

      j = cached_j;

    } else if ((cached_j + 1 < len) && (r == _regions.at(cached_j + 1))) {

      j = cached_j + 1;

    } else {

      j = find(r);

#endif

      if (j < 0) {

        j = 0;

      }

#if 0

    }

#endif

  }

  int i;

  for (i = j; i < len; i += 1) {

    int res = blk->doHeapRegion(_regions.at(i));

    if (res) {

#if 0

      cached_j = i;

#endif

      blk->incomplete();

      return;

    }

  }

  for (i = 0; i < j; i += 1) {

    int res = blk->doHeapRegion(_regions.at(i));

    if (res) {

#if 0

      cached_j = i;

#endif

      blk->incomplete();

      return;

    }

  }

}

void HeapRegionSeq::iterate_from(int idx, HeapRegionClosure* blk) {

  int len = _regions.length();

  int i;

  for (i = idx; i < len; i++) {

    if (blk->doHeapRegion(_regions.at(i))) {

      blk->incomplete();

      return;

    }

  }

  for (i = 0; i < idx; i++) {

    if (blk->doHeapRegion(_regions.at(i))) {

      blk->incomplete();

      return;

    }

  }

}

MemRegion HeapRegionSeq::shrink_by(size_t shrink_bytes,

                                   size_t& num_regions_deleted) {

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

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

  if (_regions.length() == 0) {

    num_regions_deleted = 0;

    return MemRegion();

  }

  int j = _regions.length() - 1;

  HeapWord* end = _regions.at(j)->end();

  HeapWord* last_start = end;

  while (j >= 0 && shrink_bytes > 0) {

    HeapRegion* cur = _regions.at(j);

    // We have to leave humongous regions where they are,

    // and work around them.

    if (cur->isHumongous()) {

      return MemRegion(last_start, end);

    }

    assert(cur == _regions.top(), "Should be top");

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

    cur->reset_zero_fill();

    shrink_bytes -= cur->capacity();

    num_regions_deleted++;

    _regions.pop();

    last_start = cur->bottom();

    // We need to delete these somehow, but can't currently do so here: if

    // we do, the ZF thread may still access the deleted region.  We'll

    // leave this here as a reminder that we have to do something about

    // this.

    // delete cur;

    j--;

  }

  return MemRegion(last_start, end);

}

class PrintHeapRegionClosure : public  HeapRegionClosure {

public:

  bool doHeapRegion(HeapRegion* r) {

    gclog_or_tty->print(PTR_FORMAT ":", r);

    r->print();

    return false;

  }

};

void HeapRegionSeq::print() {

  PrintHeapRegionClosure cl;

  iterate(&cl);

}