/*

 * 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/collectionSetChooser.hpp"

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

#include "gc_implementation/g1/g1CollectorPolicy.hpp"

#include "gc_implementation/g1/g1ErgoVerbose.hpp"

#include "memory/space.inline.hpp"

CSetChooserCache::CSetChooserCache() {

  for (int i = 0; i < CacheLength; ++i)

    _cache[i] = NULL;

  clear();

}

void CSetChooserCache::clear() {

  _occupancy = 0;

  _first = 0;

  for (int i = 0; i < CacheLength; ++i) {

    HeapRegion *hr = _cache[i];

    if (hr != NULL)

      hr->set_sort_index(-1);

    _cache[i] = NULL;

  }

}

#ifndef PRODUCT

bool CSetChooserCache::verify() {

  guarantee(false, "CSetChooserCache::verify(): don't call this any more");

  int index = _first;

  HeapRegion *prev = NULL;

  for (int i = 0; i < _occupancy; ++i) {

    guarantee(_cache[index] != NULL, "cache entry should not be empty");

    HeapRegion *hr = _cache[index];

    guarantee(!hr->is_young(), "should not be young!");

    if (prev != NULL) {

      guarantee(prev->gc_efficiency() >= hr->gc_efficiency(),

                "cache should be correctly ordered");

    }

    guarantee(hr->sort_index() == get_sort_index(index),

              "sort index should be correct");

    index = trim_index(index + 1);

    prev = hr;

  }

  for (int i = 0; i < (CacheLength - _occupancy); ++i) {

    guarantee(_cache[index] == NULL, "cache entry should be empty");

    index = trim_index(index + 1);

  }

  guarantee(index == _first, "we should have reached where we started from");

  return true;

}

#endif // PRODUCT

void CSetChooserCache::insert(HeapRegion *hr) {

  guarantee(false, "CSetChooserCache::insert(): don't call this any more");

  assert(!is_full(), "cache should not be empty");

  hr->calc_gc_efficiency();

  int empty_index;

  if (_occupancy == 0) {

    empty_index = _first;

  } else {

    empty_index = trim_index(_first + _occupancy);

    assert(_cache[empty_index] == NULL, "last slot should be empty");

    int last_index = trim_index(empty_index - 1);

    HeapRegion *last = _cache[last_index];

    assert(last != NULL,"as the cache is not empty, last should not be empty");

    while (empty_index != _first &&

           last->gc_efficiency() < hr->gc_efficiency()) {

      _cache[empty_index] = last;

      last->set_sort_index(get_sort_index(empty_index));

      empty_index = last_index;

      last_index = trim_index(last_index - 1);

      last = _cache[last_index];

    }

  }

  _cache[empty_index] = hr;

  hr->set_sort_index(get_sort_index(empty_index));

  ++_occupancy;

  assert(verify(), "cache should be consistent");

}

HeapRegion *CSetChooserCache::remove_first() {

  guarantee(false, "CSetChooserCache::remove_first(): "

                   "don't call this any more");

  if (_occupancy > 0) {

    assert(_cache[_first] != NULL, "cache should have at least one region");

    HeapRegion *ret = _cache[_first];

    _cache[_first] = NULL;

    ret->set_sort_index(-1);

    --_occupancy;

    _first = trim_index(_first + 1);

    assert(verify(), "cache should be consistent");

    return ret;

  } else {

    return NULL;

  }

}

// Even though we don't use the GC efficiency in our heuristics as

// much as we used to, we still order according to GC efficiency. This

// will cause regions with a lot of live objects and large RSets to

// end up at the end of the array. Given that we might skip collecting

// the last few old regions, if after a few mixed GCs the remaining

// have reclaimable bytes under a certain threshold, the hope is that

// the ones we'll skip are ones with both large RSets and a lot of

// live objects, not the ones with just a lot of live objects if we

// ordered according to the amount of reclaimable bytes per region.

static int orderRegions(HeapRegion* hr1, HeapRegion* hr2) {

  if (hr1 == NULL) {

    if (hr2 == NULL) {

      return 0;

    } else {

      return 1;

    }

  } else if (hr2 == NULL) {

    return -1;

  }

  double gc_eff1 = hr1->gc_efficiency();

  double gc_eff2 = hr2->gc_efficiency();

  if (gc_eff1 > gc_eff2) {

    return -1;

  } if (gc_eff1 < gc_eff2) {

    return 1;

  } else {

    return 0;

  }

}

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

  return orderRegions(*hr1p, *hr2p);

}

CollectionSetChooser::CollectionSetChooser() :

  // 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.

  //

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

                                             ResourceObj::C_HEAP),

                  100), true /* C_Heap */),

    _curr_index(0), _length(0),

    _regionLiveThresholdBytes(0), _remainingReclaimableBytes(0),

    _first_par_unreserved_idx(0) {

  _regionLiveThresholdBytes =

    HeapRegion::GrainBytes * (size_t) G1OldCSetRegionLiveThresholdPercent / 100;

}

#ifndef PRODUCT

bool CollectionSetChooser::verify() {

  guarantee(_length >= 0, err_msg("_length: %d", _length));

  guarantee(0 <= _curr_index && _curr_index <= _length,

            err_msg("_curr_index: %d _length: %d", _curr_index, _length));

  int index = 0;

  size_t sum_of_reclaimable_bytes = 0;

  while (index < _curr_index) {

    guarantee(_markedRegions.at(index) == NULL,

              "all entries before _curr_index should be NULL");

    index += 1;

  }

  HeapRegion *prev = NULL;

  while (index < _length) {

    HeapRegion *curr = _markedRegions.at(index++);

    guarantee(curr != NULL, "Regions in _markedRegions array cannot be NULL");

    int si = curr->sort_index();

    guarantee(!curr->is_young(), "should not be young!");

    guarantee(!curr->isHumongous(), "should not be humongous!");

    guarantee(si > -1 && si == (index-1), "sort index invariant");

    if (prev != NULL) {

      guarantee(orderRegions(prev, curr) != 1,

                err_msg("GC eff prev: %1.4f GC eff curr: %1.4f",

                        prev->gc_efficiency(), curr->gc_efficiency()));

    }

    sum_of_reclaimable_bytes += curr->reclaimable_bytes();

    prev = curr;

  }

  guarantee(sum_of_reclaimable_bytes == _remainingReclaimableBytes,

            err_msg("reclaimable bytes inconsistent, "

                    "remaining: "SIZE_FORMAT" sum: "SIZE_FORMAT,

                    _remainingReclaimableBytes, sum_of_reclaimable_bytes));

  return true;

}

#endif

void CollectionSetChooser::fillCache() {

  guarantee(false, "fillCache: don't call this any more");

  while (!_cache.is_full() && (_curr_index < _length)) {

    HeapRegion* hr = _markedRegions.at(_curr_index);

    assert(hr != NULL,

           err_msg("Unexpected NULL hr in _markedRegions at index %d",

                   _curr_index));

    _curr_index += 1;

    assert(!hr->is_young(), "should not be young!");

    assert(hr->sort_index() == _curr_index-1, "sort_index invariant");

    _markedRegions.at_put(hr->sort_index(), NULL);

    _cache.insert(hr);

    assert(!_cache.is_empty(), "cache should not be empty");

  }

  assert(verify(), "cache should be consistent");

}

void CollectionSetChooser::sortMarkedHeapRegions() {

  // First trim any unused portion of the top in the parallel case.

  if (_first_par_unreserved_idx > 0) {

    if (G1PrintParCleanupStats) {

      gclog_or_tty->print("     Truncating _markedRegions from %d to %d.\n",

                          _markedRegions.length(), _first_par_unreserved_idx);

    }

    assert(_first_par_unreserved_idx <= _markedRegions.length(),

           "Or we didn't reserved enough length");

    _markedRegions.trunc_to(_first_par_unreserved_idx);

  }

  _markedRegions.sort(orderRegions);

  assert(_length <= _markedRegions.length(), "Requirement");

  assert(_length == 0 || _markedRegions.at(_length - 1) != NULL,

         "Testing _length");

  assert(_length == _markedRegions.length() ||

                        _markedRegions.at(_length) == NULL, "Testing _length");

  if (G1PrintParCleanupStats) {

    gclog_or_tty->print_cr("     Sorted %d marked regions.", _length);

  }

  for (int i = 0; i < _length; i++) {

    assert(_markedRegions.at(i) != NULL, "Should be true by sorting!");

    _markedRegions.at(i)->set_sort_index(i);

  }

  if (G1PrintRegionLivenessInfo) {

    G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Sorting");

    for (int i = 0; i < _length; ++i) {

      HeapRegion* r = _markedRegions.at(i);

      cl.doHeapRegion(r);

    }

  }

  assert(verify(), "CSet chooser verification");

}

  // The min old CSet region bound is based on the maximum desired

  // number of mixed GCs after a cycle. I.e., even if some old regions

  // look expensive, we should add them to the CSet anyway to make

  // sure we go through the available old regions in no more than the

  // maximum desired number of mixed GCs.

  //

  // The calculation is based on the number of marked regions we added

  // to the CSet chooser in the first place, not how many remain, so

  // that the result is the same during all mixed GCs that follow a cycle.

  const size_t region_num = (size_t) _length;

  const size_t gc_num = (size_t) G1MixedGCCountTarget;

  size_t result = region_num / gc_num;

  // emulate ceiling

  if (result * gc_num < region_num) {

    result += 1;

  }

}

  // The max old CSet region bound is based on the threshold expressed

  // as a percentage of the heap size. I.e., it should bound the

  // number of old regions added to the CSet irrespective of how many

  // of them are available.

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  const size_t region_num = g1h->n_regions();

  const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;

  size_t result = region_num * perc / 100;

  // emulate ceiling

  if (100 * result < region_num * perc) {

    result += 1;

  }

}

void CollectionSetChooser::addMarkedHeapRegion(HeapRegion* hr) {

  assert(!hr->isHumongous(),

         "Humongous regions shouldn't be added to the collection set");

  assert(!hr->is_young(), "should not be young!");

  _markedRegions.append(hr);

  _length++;

  _remainingReclaimableBytes += hr->reclaimable_bytes();

  hr->calc_gc_efficiency();

}

  _first_par_unreserved_idx = 0;

  if (UseDynamicNumberOfGCThreads) {

    assert(G1CollectedHeap::heap()->workers()->active_workers() > 0,

      "Should have been set earlier");

    // This is defensive code. As the assertion above says, the number

    // of active threads should be > 0, but in case there is some path

    // or some improperly initialized variable with leads to no

    // active threads, protect against that in a product build.

    n_threads = MAX2(G1CollectedHeap::heap()->workers()->active_workers(),

                     1U);

  }

  // it should be aligned with respect to chunkSize

}

jint CollectionSetChooser::getParMarkedHeapRegionChunk(jint n_regions) {

  // Don't do this assert because this can be called at a point

  // where the loop up stream will not execute again but might

  // try to claim more chunks (loop test has not been done yet).

  // assert(_markedRegions.length() > _first_par_unreserved_idx,

  //  "Striding beyond the marked regions");

  jint res = Atomic::add(n_regions, &_first_par_unreserved_idx);

  assert(_markedRegions.length() > res + n_regions - 1,

         "Should already have been expanded");

  return res - n_regions;

}

void CollectionSetChooser::setMarkedHeapRegion(jint index, HeapRegion* hr) {

  assert(_markedRegions.at(index) == NULL, "precondition");

  assert(!hr->is_young(), "should not be young!");

  _markedRegions.at_put(index, hr);

  hr->calc_gc_efficiency();

}

void CollectionSetChooser::updateTotals(jint region_num,

                                        size_t reclaimable_bytes) {

  // Only take the lock if we actually need to update the totals.

  if (region_num > 0) {

    assert(reclaimable_bytes > 0, "invariant");

    // We could have just used atomics instead of taking the

    // lock. However, we currently don't have an atomic add for size_t.

    MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);

    _length += (int) region_num;

    _remainingReclaimableBytes += reclaimable_bytes;

  } else {

    assert(reclaimable_bytes == 0, "invariant");

  }

}

void CollectionSetChooser::clearMarkedHeapRegions() {

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

    HeapRegion* r = _markedRegions.at(i);

    if (r != NULL) {

      r->set_sort_index(-1);

    }

  }

  _markedRegions.clear();

  _curr_index = 0;

  _length = 0;

  _remainingReclaimableBytes = 0;

};