/*

 * Copyright (c) 2013, 2019, 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/g1/g1CardTableEntryClosure.hpp"

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

#include "gc/g1/g1DirtyCardQueue.hpp"

#include "gc/g1/g1HotCardCache.hpp"

#include "runtime/atomic.hpp"

G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h):

  _g1h(g1h), _use_cache(false), _card_counts(g1h),

  _hot_cache(NULL), _hot_cache_size(0), _hot_cache_par_chunk_size(0),

{}

void G1HotCardCache::initialize(G1RegionToSpaceMapper* card_counts_storage) {

  if (default_use_cache()) {

    _use_cache = true;

    _hot_cache_size = (size_t)1 << G1ConcRSLogCacheSize;

    _hot_cache = ArrayAllocator<CardValue*>::allocate(_hot_cache_size, mtGC);

    reset_hot_cache_internal();

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

    _hot_cache_par_chunk_size = ClaimChunkSize;

    _hot_cache_par_claimed_idx = 0;

    _card_counts.initialize(card_counts_storage);

  }

}

G1HotCardCache::~G1HotCardCache() {

  if (default_use_cache()) {

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

    ArrayAllocator<CardValue*>::free(_hot_cache, _hot_cache_size);

    _hot_cache = NULL;

  }

}

CardTable::CardValue* G1HotCardCache::insert(CardValue* card_ptr) {

  uint count = _card_counts.add_card_count(card_ptr);

  if (!_card_counts.is_hot(count)) {

    // The card is not hot so do not store it in the cache;

    // return it for immediate refining.

    return card_ptr;

  }

  // Otherwise, the card is hot.

  size_t index = Atomic::add(&_hot_cache_idx, 1u) - 1;

  size_t masked_index = index & (_hot_cache_size - 1);

  CardValue* current_ptr = _hot_cache[masked_index];

  // Try to store the new card pointer into the cache. Compare-and-swap to guard

  // against the unlikely event of a race resulting in another card pointer to

  // have already been written to the cache. In this case we will return

  // card_ptr in favor of the other option, which would be starting over. This

  // should be OK since card_ptr will likely be the older card already when/if

  // this ever happens.

  CardValue* previous_ptr = Atomic::cmpxchg(&_hot_cache[masked_index],

                                            current_ptr,

                                            card_ptr);

  return (previous_ptr == current_ptr) ? previous_ptr : card_ptr;

}

void G1HotCardCache::drain(G1CardTableEntryClosure* cl, uint worker_id) {

  assert(default_use_cache(), "Drain only necessary if we use the hot card cache.");

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

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

  while (_hot_cache_par_claimed_idx < _hot_cache_size) {

    size_t end_idx = Atomic::add(&_hot_cache_par_claimed_idx,

                                 _hot_cache_par_chunk_size);

    size_t start_idx = end_idx - _hot_cache_par_chunk_size;

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

    end_idx = MIN2(end_idx, _hot_cache_size);

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

      CardValue* card_ptr = _hot_cache[i];

      if (card_ptr != NULL) {

        cl->do_card_ptr(card_ptr, worker_id);

      } else {

        break;

      }

    }

  }

  // The existing entries in the hot card cache, which were just refined

  // above, are discarded prior to re-enabling the cache near the end of the GC.

}

void G1HotCardCache::reset_card_counts(HeapRegion* hr) {

  _card_counts.clear_region(hr);

}