/*

 * Copyright (c) 2001, 2011, 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/concurrentG1Refine.hpp"

#include "gc_implementation/g1/concurrentG1RefineThread.hpp"

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

#include "gc_implementation/g1/g1CollectorPolicy.hpp"

#include "gc_implementation/g1/g1RemSet.hpp"

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

#include "memory/space.inline.hpp"

#include "runtime/atomic.hpp"

#include "utilities/copy.hpp"

// Possible sizes for the card counts cache: odd primes that roughly double in size.

// (See jvmtiTagMap.cpp).

  };

ConcurrentG1Refine::ConcurrentG1Refine() :

  _card_counts(NULL), _card_epochs(NULL),

  _cache_size_index(0), _expand_card_counts(false),

  _hot_cache(NULL),

  _def_use_cache(false), _use_cache(false),

  _n_periods(0),

  _threads(NULL), _n_threads(0)

{

  // Ergomonically select initial concurrent refinement parameters

  if (FLAG_IS_DEFAULT(G1ConcRefinementGreenZone)) {

    FLAG_SET_DEFAULT(G1ConcRefinementGreenZone, MAX2<int>(ParallelGCThreads, 1));

  }

  set_green_zone(G1ConcRefinementGreenZone);

  if (FLAG_IS_DEFAULT(G1ConcRefinementYellowZone)) {

    FLAG_SET_DEFAULT(G1ConcRefinementYellowZone, green_zone() * 3);

  }

  set_yellow_zone(MAX2<int>(G1ConcRefinementYellowZone, green_zone()));

  if (FLAG_IS_DEFAULT(G1ConcRefinementRedZone)) {

    FLAG_SET_DEFAULT(G1ConcRefinementRedZone, yellow_zone() * 2);

  }

  set_red_zone(MAX2<int>(G1ConcRefinementRedZone, yellow_zone()));

  _n_worker_threads = thread_num();

  // We need one extra thread to do the young gen rset size sampling.

  _n_threads = _n_worker_threads + 1;

  reset_threshold_step();

  _threads = NEW_C_HEAP_ARRAY(ConcurrentG1RefineThread*, _n_threads);

  int worker_id_offset = (int)DirtyCardQueueSet::num_par_ids();

  ConcurrentG1RefineThread *next = NULL;

  for (int i = _n_threads - 1; i >= 0; i--) {

    ConcurrentG1RefineThread* t = new ConcurrentG1RefineThread(this, next, worker_id_offset, i);

    assert(t != NULL, "Conc refine should have been created");

    assert(t->cg1r() == this, "Conc refine thread should refer to this");

    _threads[i] = t;

    next = t;

  }

}

void ConcurrentG1Refine::reset_threshold_step() {

  if (FLAG_IS_DEFAULT(G1ConcRefinementThresholdStep)) {

    _thread_threshold_step = (yellow_zone() - green_zone()) / (worker_thread_num() + 1);

  } else {

    _thread_threshold_step = G1ConcRefinementThresholdStep;

  }

}

int ConcurrentG1Refine::thread_num() {

  return MAX2<int>((G1ConcRefinementThreads > 0) ? G1ConcRefinementThreads : ParallelGCThreads, 1);

}

void ConcurrentG1Refine::init() {

  if (G1ConcRSLogCacheSize > 0) {

    _g1h = G1CollectedHeap::heap();

    size_t max_card_num = ((size_t)1 << (sizeof(unsigned)*BitsPerByte-1)) - 1;

    Copy::fill_to_bytes(&_card_counts[0],

                        _n_card_counts * sizeof(CardCountCacheEntry));

    Copy::fill_to_bytes(&_card_epochs[0], _n_card_counts * sizeof(CardEpochCacheEntry));

    ModRefBarrierSet* bs = _g1h->mr_bs();

    guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");

    _ct_bs = (CardTableModRefBS*)bs;

    _ct_bot = _ct_bs->byte_for_const(_g1h->reserved_region().start());

    _def_use_cache = true;

    _use_cache = true;

    _hot_cache_size = (1 << G1ConcRSLogCacheSize);

    _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size);

    _n_hot = 0;

    _hot_cache_idx = 0;

    // For refining the cards in the hot cache in parallel

    int n_workers = (ParallelGCThreads > 0 ?

                        _g1h->workers()->total_workers() : 1);

    _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / n_workers);

    _hot_cache_par_claimed_idx = 0;

  }

}

void ConcurrentG1Refine::stop() {

  if (_threads != NULL) {

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

      _threads[i]->stop();

    }

  }

}

void ConcurrentG1Refine::reinitialize_threads() {

  reset_threshold_step();

  if (_threads != NULL) {

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

      _threads[i]->initialize();

    }

  }

}

ConcurrentG1Refine::~ConcurrentG1Refine() {

  if (G1ConcRSLogCacheSize > 0) {

    assert(_card_counts != NULL, "Logic");

    assert(_card_epochs != NULL, "Logic");

    assert(_hot_cache != NULL, "Logic");

    FREE_C_HEAP_ARRAY(jbyte*, _hot_cache);

  }

  if (_threads != NULL) {

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

      delete _threads[i];

    }

    FREE_C_HEAP_ARRAY(ConcurrentG1RefineThread*, _threads);

  }

}

void ConcurrentG1Refine::threads_do(ThreadClosure *tc) {

  if (_threads != NULL) {

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

      tc->do_thread(_threads[i]);

    }

  }

}

bool ConcurrentG1Refine::is_young_card(jbyte* card_ptr) {

  HeapWord* start = _ct_bs->addr_for(card_ptr);

  HeapRegion* r = _g1h->heap_region_containing(start);

  if (r != NULL && r->is_young()) {

    return true;

  }

  // This card is not associated with a heap region

  // so can't be young.

  return false;

}

jbyte* ConcurrentG1Refine::add_card_count(jbyte* card_ptr, int* count, bool* defer) {

  unsigned new_card_num = ptr_2_card_num(card_ptr);

  unsigned bucket = hash(new_card_num);

  assert(0 <= bucket && bucket < _n_card_counts, "Bounds");

  CardCountCacheEntry* count_ptr = &_card_counts[bucket];

  CardEpochCacheEntry* epoch_ptr = &_card_epochs[bucket];

  // We have to construct a new entry if we haven't updated the counts

  // during the current period, or if the count was updated for a

  // different card number.

  unsigned int new_epoch = (unsigned int) _n_periods;

  julong new_epoch_entry = make_epoch_entry(new_card_num, new_epoch);

  while (true) {

    // Fetch the previous epoch value

    julong prev_epoch_entry = epoch_ptr->_value;

    julong cas_res;

    if (extract_epoch(prev_epoch_entry) != new_epoch) {

      // This entry has not yet been updated during this period.

      // Note: we update the epoch value atomically to ensure

      // that there is only one winner that updates the cached

      // card_ptr value even though all the refine threads share

      // the same epoch value.

      cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry,

                                         (volatile jlong*)&epoch_ptr->_value,

                                         (jlong) prev_epoch_entry);

      if (cas_res == prev_epoch_entry) {

        // We have successfully won the race to update the

        // epoch and card_num value. Make it look like the

        // count and eviction count were previously cleared.

        count_ptr->_count = 1;

        count_ptr->_evict_count = 0;

        *count = 0;

        // We can defer the processing of card_ptr

        *defer = true;

        return card_ptr;

      }

      // We did not win the race to update the epoch field, so some other

      // thread must have done it. The value that gets returned by CAS

      // should be the new epoch value.

      assert(extract_epoch(cas_res) == new_epoch, "unexpected epoch");

      // We could 'continue' here or just re-read the previous epoch value

      prev_epoch_entry = epoch_ptr->_value;

    }

    // The epoch entry for card_ptr has been updated during this period.

    unsigned old_card_num = extract_card_num(prev_epoch_entry);

    // The card count that will be returned to caller

    *count = count_ptr->_count;

    // Are we updating the count for the same card?

    if (new_card_num == old_card_num) {

      // Same card - just update the count. We could have more than one

      // thread racing to update count for the current card. It should be

      // OK not to use a CAS as the only penalty should be some missed

      // increments of the count which delays identifying the card as "hot".

      if (*count < max_jubyte) count_ptr->_count++;

      // We can defer the processing of card_ptr

      *defer = true;

      return card_ptr;

    }

    // Different card - evict old card info

    if (count_ptr->_evict_count < max_jubyte) count_ptr->_evict_count++;

    if (count_ptr->_evict_count > G1CardCountCacheExpandThreshold) {

      // Trigger a resize the next time we clear

      _expand_card_counts = true;

    }

    cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry,

                                       (volatile jlong*)&epoch_ptr->_value,

                                       (jlong) prev_epoch_entry);

    if (cas_res == prev_epoch_entry) {

      // We successfully updated the card num value in the epoch entry

      count_ptr->_count = 0; // initialize counter for new card num

      jbyte* old_card_ptr = card_num_2_ptr(old_card_num);

      // Even though the region containg the card at old_card_num was not

      // in the young list when old_card_num was recorded in the epoch

      // cache it could have been added to the free list and subsequently

      // added to the young list in the intervening time. See CR 6817995.

      // We do not deal with this case here - it will be handled in

      // HeapRegion::oops_on_card_seq_iterate_careful after it has been

      // determined that the region containing the card has been allocated

      // to, and it's safe to check the young type of the region.

      // We do not want to defer processing of card_ptr in this case

      // (we need to refine old_card_ptr and card_ptr)

      *defer = false;

      return old_card_ptr;

    }

    // Someone else beat us - try again.

  }

}

jbyte* ConcurrentG1Refine::cache_insert(jbyte* card_ptr, bool* defer) {

  int count;

  jbyte* cached_ptr = add_card_count(card_ptr, &count, defer);

  assert(cached_ptr != NULL, "bad cached card ptr");

  // We've just inserted a card pointer into the card count cache

  // and got back the card that we just inserted or (evicted) the

  // previous contents of that count slot.

  // The card we got back could be in a young region. When the

  // returned card (if evicted) was originally inserted, we had

  // determined that its containing region was not young. However

  // it is possible for the region to be freed during a cleanup

  // pause, then reallocated and tagged as young which will result

  // in the returned card residing in a young region.

  //

  // We do not deal with this case here - the change from non-young

  // to young could be observed at any time - it will be handled in

  // HeapRegion::oops_on_card_seq_iterate_careful after it has been

  // determined that the region containing the card has been allocated

  // to.

  // The card pointer we obtained from card count cache is not hot

  // so do not store it in the cache; return it for immediate

  // refining.

  if (count < G1ConcRSHotCardLimit) {

    return cached_ptr;

  }

  // Otherwise, the pointer we got from the _card_counts cache is hot.

  jbyte* res = NULL;

  MutexLockerEx x(HotCardCache_lock, Mutex::_no_safepoint_check_flag);

  if (_n_hot == _hot_cache_size) {

    res = _hot_cache[_hot_cache_idx];

    _n_hot--;

  }

  // Now _n_hot < _hot_cache_size, and we can insert at _hot_cache_idx.

  _hot_cache[_hot_cache_idx] = cached_ptr;

  _hot_cache_idx++;

  if (_hot_cache_idx == _hot_cache_size) _hot_cache_idx = 0;

  _n_hot++;

  // The card obtained from the hot card cache could be in a young

  // region. See above on how this can happen.

  return res;

}

void ConcurrentG1Refine::clean_up_cache(int worker_i,

                                        G1RemSet* g1rs,

                                        DirtyCardQueue* into_cset_dcq) {

  assert(!use_cache(), "cache should be disabled");

  int start_idx;

  while ((start_idx = _hot_cache_par_claimed_idx) < _n_hot) { // read once

    int end_idx = start_idx + _hot_cache_par_chunk_size;

    if (start_idx ==

        Atomic::cmpxchg(end_idx, &_hot_cache_par_claimed_idx, start_idx)) {

      // The current worker has successfully claimed the chunk [start_idx..end_idx)

      end_idx = MIN2(end_idx, _n_hot);

      for (int i = start_idx; i < end_idx; i++) {

        jbyte* entry = _hot_cache[i];

        if (entry != NULL) {

          if (g1rs->concurrentRefineOneCard(entry, worker_i, true)) {

            // 'entry' contains references that point into the current

            // collection set. We need to record 'entry' in the DCQS

            // that's used for that purpose.

            //

            // The only time we care about recording cards that contain

            // references that point into the collection set is during

            // RSet updating while within an evacuation pause.

            // In this case worker_i should be the id of a GC worker thread

            assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");

            assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "incorrect worker id");

            into_cset_dcq->enqueue(entry);

          }

        }

      }

    }

  }

}

    }

  }