/*

 * Copyright 2001-2009 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/_concurrentG1Refine.cpp.incl"

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

// (See jvmtiTagMap.cpp).

int ConcurrentG1Refine::_cc_cache_sizes[] = {

        16381,    32771,    76831,    150001,   307261,

       614563,  1228891,  2457733,   4915219,  9830479,

     19660831, 39321619, 78643219, 157286461,       -1

  };

ConcurrentG1Refine::ConcurrentG1Refine() :

  _card_counts(NULL), _card_epochs(NULL),

  _n_card_counts(0), _max_n_card_counts(0),

  _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)

{

  if (G1ConcRefine) {

    _n_threads = (int)thread_num();

    if (_n_threads > 0) {

      _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;

      }

    }

  }

}

size_t ConcurrentG1Refine::thread_num() {

  if (G1ConcRefine) {

    return (G1ParallelRSetThreads > 0) ? G1ParallelRSetThreads : ParallelGCThreads;

  }

  return 0;

}

void ConcurrentG1Refine::init() {

  if (G1ConcRSLogCacheSize > 0) {

    _g1h = G1CollectedHeap::heap();

    _max_n_card_counts =

      (unsigned) (_g1h->g1_reserved_obj_bytes() >> CardTableModRefBS::card_shift);

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

    guarantee(_max_n_card_counts < max_card_num, "card_num representation");

    int desired = _max_n_card_counts / InitialCacheFraction;

    for (_cache_size_index = 0;

              _cc_cache_sizes[_cache_size_index] >= 0; _cache_size_index++) {

      if (_cc_cache_sizes[_cache_size_index] >= desired) break;

    }

    _cache_size_index = MAX2(0, (_cache_size_index - 1));

    int initial_size = _cc_cache_sizes[_cache_size_index];

    if (initial_size < 0) initial_size = _max_n_card_counts;

    // Make sure we don't go bigger than we will ever need

    _n_card_counts = MIN2((unsigned) initial_size, _max_n_card_counts);

    _card_counts = NEW_C_HEAP_ARRAY(CardCountCacheEntry, _n_card_counts);

    _card_epochs = NEW_C_HEAP_ARRAY(CardEpochCacheEntry, _n_card_counts);

    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();

    }

  }

}

ConcurrentG1Refine::~ConcurrentG1Refine() {

  if (G1ConcRSLogCacheSize > 0) {

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

    FREE_C_HEAP_ARRAY(CardCountCacheEntry, _card_counts);

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

    FREE_C_HEAP_ARRAY(CardEpochCacheEntry, _card_epochs);

    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

      // 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. If the evicted

      // card is in a young region just return the card_ptr and the evicted

      // card will not be cleaned. See CR 6817995.

      jbyte* old_card_ptr = card_num_2_ptr(old_card_num);

      if (is_young_card(old_card_ptr)) {

        *count = 0;

        // We can defer the processing of card_ptr

        *defer = true;

        return card_ptr;

      }

      // 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");

  assert(!is_young_card(cached_ptr), "shouldn't get a card in young region");

  // 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 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++;

  if (res != NULL) {

    // Even though the region containg res was not in the young list

    // when it was recorded in the hot cache it could have been added

    // to the free list and subsequently added to the young list in

    // the intervening time. If res is in a young region, return NULL

    // so that res is not cleaned. See CR 6817995.

    if (is_young_card(res)) {

      res = NULL;

    }

  }

  return res;

}

void ConcurrentG1Refine::clean_up_cache(int worker_i, G1RemSet* g1rs) {

  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) {

          g1rs->concurrentRefineOneCard(entry, worker_i);

        }

      }

    }

  }

}

void ConcurrentG1Refine::expand_card_count_cache() {

  if (_n_card_counts < _max_n_card_counts) {

    int new_idx = _cache_size_index+1;

    int new_size = _cc_cache_sizes[new_idx];

    if (new_size < 0) new_size = _max_n_card_counts;

    // Make sure we don't go bigger than we will ever need

    new_size = MIN2((unsigned) new_size, _max_n_card_counts);

    // Expand the card count and card epoch tables

    if (new_size > (int)_n_card_counts) {

      // We can just free and allocate a new array as we're

      // not interested in preserving the contents

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

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

      FREE_C_HEAP_ARRAY(CardCountCacheEntry, _card_counts);

      FREE_C_HEAP_ARRAY(CardEpochCacheEntry, _card_epochs);

      _n_card_counts = new_size;

      _card_counts = NEW_C_HEAP_ARRAY(CardCountCacheEntry, _n_card_counts);

      _card_epochs = NEW_C_HEAP_ARRAY(CardEpochCacheEntry, _n_card_counts);

      _cache_size_index = new_idx;

    }

  }

}

void ConcurrentG1Refine::clear_and_record_card_counts() {

  if (G1ConcRSLogCacheSize == 0) return;

#ifndef PRODUCT

  double start = os::elapsedTime();

#endif

  if (_expand_card_counts) {

    expand_card_count_cache();

    _expand_card_counts = false;

    // Only need to clear the epochs.

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

  }

  int this_epoch = (int) _n_periods;

  assert((this_epoch+1) <= max_jint, "to many periods");

  // Update epoch

  _n_periods++;

#ifndef PRODUCT

  double elapsed = os::elapsedTime() - start;

  _g1h->g1_policy()->record_cc_clear_time(elapsed * 1000.0);

#endif

}