/*

 * 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

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 */

#include "memory/allocation.hpp"

#include "utilities/ostream.hpp"

// G1FromCardCache remembers the most recently processed card on the heap on

// a per-region and per-thread basis.

class G1FromCardCache : public AllStatic {

private:

  // Array of card indices. Indexed by heap region (rows) and thread (columns) to minimize

  // thread contention.

  // This order minimizes the time to clear all entries for a given region during region

  // freeing. I.e. a single clear of a single memory area instead of multiple separate

  // accesses with a large stride per region.

  static uintptr_t** _cache;

  static uint _max_regions;

  static size_t _static_mem_size;

#ifdef ASSERT

  static uint _max_workers;

  static void check_bounds(uint worker_id, uint region_idx) {

    assert(worker_id < _max_workers, "Worker_id %u is larger than maximum %u", worker_id, _max_workers);

    assert(region_idx < _max_regions, "Region_idx %u is larger than maximum %u", region_idx, _max_regions);

  }

#endif

  // This card index indicates "no card for that entry" yet. This allows us to use the OS

  // lazy backing of memory with zero-filled pages to avoid initial actual memory use.

  // This means that the heap must not contain card zero.

  static const uintptr_t InvalidCard = 0;

public:

  static void clear(uint region_idx);

  // Returns true if the given card is in the cache at the given location, or

  // replaces the card at that location and returns false.

  static bool contains_or_replace(uint worker_id, uint region_idx, uintptr_t card) {

    uintptr_t card_in_cache = at(worker_id, region_idx);

    if (card_in_cache == card) {

      return true;

    } else {

      set(worker_id, region_idx, card);

      return false;

    }

  }

  static uintptr_t at(uint worker_id, uint region_idx) {

    DEBUG_ONLY(check_bounds(worker_id, region_idx);)

    return _cache[region_idx][worker_id];

  }

  static void set(uint worker_id, uint region_idx, uintptr_t val) {

    DEBUG_ONLY(check_bounds(worker_id, region_idx);)

    _cache[region_idx][worker_id] = val;

  }

  static void initialize(uint num_par_rem_sets, uint max_num_regions);

  static void invalidate(uint start_idx, size_t num_regions);

  static void print(outputStream* out = tty) PRODUCT_RETURN;

  static size_t static_mem_size() {

    return _static_mem_size;

  }

};