/*

 * Copyright (c) 2015, 2018, 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/z/zHeap.inline.hpp"

#include "gc/z/zLiveMap.inline.hpp"

#include "gc/z/zStat.hpp"

#include "gc/z/zThread.hpp"

#include "logging/log.hpp"

#include "runtime/atomic.hpp"

#include "runtime/orderAccess.hpp"

#include "utilities/debug.hpp"

static const ZStatCounter ZCounterMarkSeqNumResetContention("Contention", "Mark SeqNum Reset Contention", ZStatUnitOpsPerSecond);

static const ZStatCounter ZCounterMarkSegmentResetContention("Contention", "Mark Segment Reset Contention", ZStatUnitOpsPerSecond);

ZLiveMap::ZLiveMap(uint32_t size) :

    _seqnum(0),

    _live_objects(0),

    _live_bytes(0),

    _segment_live_bits(0),

    _segment_claim_bits(0),

    // We need at least one bit per segment.

    _bitmap(MAX2<size_t>(size, nsegments) * 2),

    _shift(exact_log2(segment_size())) {}

void ZLiveMap::reset(size_t index) {

  const uint32_t seqnum_initializing = (uint32_t)-1;

  bool contention = false;

  // Multiple threads can enter here, make sure only one of them

  // resets the marking information while the others busy wait.

  for (uint32_t seqnum = _seqnum; seqnum != ZGlobalSeqNum; seqnum = _seqnum) {

    if ((seqnum != seqnum_initializing) &&

        (Atomic::cmpxchg(seqnum_initializing, &_seqnum, seqnum) == seqnum)) {

      // Reset marking information

      _live_bytes = 0;

      _live_objects = 0;

      // Clear segment claimed/live bits

      segment_live_bits().clear();

      segment_claim_bits().clear();

      // Make sure the newly reset marking information is

      // globally visible before updating the page seqnum.

      OrderAccess::storestore();

      // Update seqnum

      assert(_seqnum == seqnum_initializing, "Invalid");

      _seqnum = ZGlobalSeqNum;

      break;

    }

    // Mark reset contention

    if (!contention) {

      // Count contention once, not every loop

      ZStatInc(ZCounterMarkSeqNumResetContention);

      contention = true;

      log_trace(gc)("Mark seqnum reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", bit: " SIZE_FORMAT,

                    ZThread::id(), ZThread::name(), p2i(this), index);

    }

  }

}

void ZLiveMap::reset_segment(BitMap::idx_t segment) {

  bool contention = false;

  if (!claim_segment(segment)) {

    // Already claimed, wait for live bit to be set

    while (!is_segment_live(segment)) {

      // Busy wait. The loadload barrier is needed to make

      // sure we re-read the live bit every time we loop.

      OrderAccess::loadload();

      // Mark reset contention

      if (!contention) {

        // Count contention once, not every loop

        ZStatInc(ZCounterMarkSegmentResetContention);

        contention = true;

        log_trace(gc)("Mark segment reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", segment: " SIZE_FORMAT,

                      ZThread::id(), ZThread::name(), p2i(this), segment);

      }

    }

    // Segment is live

    return;

  }

  // Segment claimed, clear it

  const BitMap::idx_t start_index = segment_start(segment);

  const BitMap::idx_t end_index   = segment_end(segment);

  if (segment_size() / BitsPerWord >= 32) {

    _bitmap.clear_large_range(start_index, end_index);

  } else {

    _bitmap.clear_range(start_index, end_index);

  }

  // Set live bit

  const bool success = set_segment_live_atomic(segment);

  assert(success, "Should never fail");

}