/*

 * Copyright (c) 2014, 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 "classfile/javaClasses.hpp"

#include "gc_implementation/g1/g1StringDedupQueue.hpp"

#include "memory/gcLocker.hpp"

#include "runtime/mutexLocker.hpp"

#include "utilities/stack.inline.hpp"

G1StringDedupQueue* G1StringDedupQueue::_queue = NULL;

const size_t        G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue

const size_t        G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue

G1StringDedupQueue::G1StringDedupQueue() :

  _cursor(0),

  _cancel(false),

  _empty(true),

  _dropped(0) {

  _nqueues = MAX2(ParallelGCThreads, (size_t)1);

  _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC);

  for (size_t i = 0; i < _nqueues; i++) {

    new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size);

  }

}

G1StringDedupQueue::~G1StringDedupQueue() {

  ShouldNotReachHere();

}

void G1StringDedupQueue::create() {

  assert(_queue == NULL, "One string deduplication queue allowed");

  _queue = new G1StringDedupQueue();

}

void G1StringDedupQueue::wait() {

  MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);

  while (_queue->_empty && !_queue->_cancel) {

    ml.wait(Mutex::_no_safepoint_check_flag);

  }

}

void G1StringDedupQueue::cancel_wait() {

  MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);

  _queue->_cancel = true;

  ml.notify();

}

void G1StringDedupQueue::push(uint worker_id, oop java_string) {

  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");

  assert(worker_id < _queue->_nqueues, "Invalid queue");

  // Push and notify waiter

  G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id];

  if (!worker_queue.is_full()) {

    worker_queue.push(java_string);

    if (_queue->_empty) {

      MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);

      if (_queue->_empty) {

        // Mark non-empty and notify waiter

        _queue->_empty = false;

        ml.notify();

      }

    }

  } else {

    // Queue is full, drop the string and update the statistics

    Atomic::inc_ptr(&_queue->_dropped);

  }

}

oop G1StringDedupQueue::pop() {

  assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint");

  No_Safepoint_Verifier nsv;

  // Try all queues before giving up

  for (size_t tries = 0; tries < _queue->_nqueues; tries++) {

    // The cursor indicates where we left of last time

    G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor];

    while (!queue->is_empty()) {

      oop obj = queue->pop();

      // The oop we pop can be NULL if it was marked

      // dead. Just ignore those and pop the next oop.

      if (obj != NULL) {

        return obj;

      }

    }

    // Try next queue

    _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues;

  }

  // Mark empty

  _queue->_empty = true;

  return NULL;

}

void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) {

  // A worker thread first claims a queue, which ensures exclusive

  // access to that queue, then continues to process it.

  for (;;) {

    // Grab next queue to scan

    size_t queue = cl->claim_queue();

    if (queue >= _queue->_nqueues) {

      // End of queues

      break;

    }

    // Scan the queue

    unlink_or_oops_do(cl, queue);

  }

}

void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) {

  assert(queue < _queue->_nqueues, "Invalid queue");

  StackIterator<oop, mtGC> iter(_queue->_queues[queue]);

  while (!iter.is_empty()) {

    oop* p = iter.next_addr();

    if (*p != NULL) {

      if (cl->is_alive(*p)) {

        cl->keep_alive(p);

      } else {

        // Clear dead reference

        *p = NULL;

      }

    }

  }

}

void G1StringDedupQueue::print_statistics(outputStream* st) {

  st->print_cr(

    "   [Queue]\n"

    "      [Dropped: "UINTX_FORMAT"]", _queue->_dropped);

}

void G1StringDedupQueue::verify() {

  for (size_t i = 0; i < _queue->_nqueues; i++) {

    StackIterator<oop, mtGC> iter(_queue->_queues[i]);

    while (!iter.is_empty()) {

      oop obj = iter.next();

      if (obj != NULL) {

        guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap");

        guarantee(!obj->is_forwarded(), "Object must not be forwarded");

        guarantee(java_lang_String::is_instance(obj), "Object must be a String");

      }

    }

  }

}