/*

 * Copyright (c) 2014, 2015, 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.inline.hpp"

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

#include "gc/g1/g1GCPhaseTimes.hpp"

#include "gc/g1/g1StringDedup.hpp"

#include "gc/g1/g1StringDedupQueue.hpp"

#include "gc/g1/g1StringDedupStat.hpp"

#include "gc/g1/g1StringDedupTable.hpp"

#include "gc/g1/g1StringDedupThread.hpp"

#include "runtime/atomic.inline.hpp"

bool G1StringDedup::_enabled = false;

void G1StringDedup::initialize() {

  assert(UseG1GC, "String deduplication only available with G1");

  if (UseStringDeduplication) {

    _enabled = true;

    G1StringDedupQueue::create();

    G1StringDedupTable::create();

    G1StringDedupThread::create();

  }

}

void G1StringDedup::stop() {

  assert(is_enabled(), "String deduplication not enabled");

  G1StringDedupThread::stop();

}

bool G1StringDedup::is_candidate_from_mark(oop obj) {

  if (java_lang_String::is_instance_inlined(obj)) {

    bool from_young = G1CollectedHeap::heap()->heap_region_containing(obj)->is_young();

    if (from_young && obj->age() < StringDeduplicationAgeThreshold) {

      // Candidate found. String is being evacuated from young to old but has not

      // reached the deduplication age threshold, i.e. has not previously been a

      // candidate during its life in the young generation.

      return true;

    }

  }

  // Not a candidate

  return false;

}

void G1StringDedup::enqueue_from_mark(oop java_string) {

  assert(is_enabled(), "String deduplication not enabled");

  if (is_candidate_from_mark(java_string)) {

    G1StringDedupQueue::push(0 /* worker_id */, java_string);

  }

}

bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {

  if (from_young && java_lang_String::is_instance_inlined(obj)) {

    if (to_young && obj->age() == StringDeduplicationAgeThreshold) {

      // Candidate found. String is being evacuated from young to young and just

      // reached the deduplication age threshold.

      return true;

    }

    if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {

      // Candidate found. String is being evacuated from young to old but has not

      // reached the deduplication age threshold, i.e. has not previously been a

      // candidate during its life in the young generation.

      return true;

    }

  }

  // Not a candidate

  return false;

}

void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {

  assert(is_enabled(), "String deduplication not enabled");

  if (is_candidate_from_evacuation(from_young, to_young, java_string)) {

    G1StringDedupQueue::push(worker_id, java_string);

  }

}

void G1StringDedup::deduplicate(oop java_string) {

  assert(is_enabled(), "String deduplication not enabled");

  G1StringDedupStat dummy; // Statistics from this path is never used

  G1StringDedupTable::deduplicate(java_string, dummy);

}

void G1StringDedup::oops_do(OopClosure* keep_alive) {

  assert(is_enabled(), "String deduplication not enabled");

  unlink_or_oops_do(NULL, keep_alive, true /* allow_resize_and_rehash */);

}

void G1StringDedup::unlink(BoolObjectClosure* is_alive) {

  assert(is_enabled(), "String deduplication not enabled");

  // Don't allow a potential resize or rehash during unlink, as the unlink

  // operation itself might remove enough entries to invalidate such a decision.

  unlink_or_oops_do(is_alive, NULL, false /* allow_resize_and_rehash */);

}

//

// Task for parallel unlink_or_oops_do() operation on the deduplication queue

// and table.

//

class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask {

private:

  G1StringDedupUnlinkOrOopsDoClosure _cl;

  G1GCPhaseTimes* _phase_times;

public:

  G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,

                                  OopClosure* keep_alive,

                                  bool allow_resize_and_rehash,

                                  G1GCPhaseTimes* phase_times) :

    AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"),

    _cl(is_alive, keep_alive, allow_resize_and_rehash), _phase_times(phase_times) { }

  virtual void work(uint worker_id) {

    {

      G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);

      G1StringDedupQueue::unlink_or_oops_do(&_cl);

    }

    {

      G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);

      G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id);

    }

  }

};

void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive,

                                      OopClosure* keep_alive,

                                      bool allow_resize_and_rehash,

                                      G1GCPhaseTimes* phase_times) {

  assert(is_enabled(), "String deduplication not enabled");

  G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash, phase_times);

  G1CollectedHeap* g1h = G1CollectedHeap::heap();

  g1h->workers()->run_task(&task);

}

void G1StringDedup::threads_do(ThreadClosure* tc) {

  assert(is_enabled(), "String deduplication not enabled");

  tc->do_thread(G1StringDedupThread::thread());

}

void G1StringDedup::print_worker_threads_on(outputStream* st) {

  assert(is_enabled(), "String deduplication not enabled");

  G1StringDedupThread::thread()->print_on(st);

  st->cr();

}

void G1StringDedup::verify() {

  assert(is_enabled(), "String deduplication not enabled");

  G1StringDedupQueue::verify();

  G1StringDedupTable::verify();

}

G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,

                                                                       OopClosure* keep_alive,

                                                                       bool allow_resize_and_rehash) :

  _is_alive(is_alive),

  _keep_alive(keep_alive),

  _resized_table(NULL),

  _rehashed_table(NULL),

  _next_queue(0),

  _next_bucket(0) {

  if (allow_resize_and_rehash) {

    // If both resize and rehash is needed, only do resize. Rehash of

    // the table will eventually happen if the situation persists.

    _resized_table = G1StringDedupTable::prepare_resize();

    if (!is_resizing()) {

      _rehashed_table = G1StringDedupTable::prepare_rehash();

    }

  }

}

G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() {

  assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");

  if (is_resizing()) {

    G1StringDedupTable::finish_resize(_resized_table);

  } else if (is_rehashing()) {

    G1StringDedupTable::finish_rehash(_rehashed_table);

  }

}

// Atomically claims the next available queue for exclusive access by

// the current thread. Returns the queue number of the claimed queue.

size_t G1StringDedupUnlinkOrOopsDoClosure::claim_queue() {

  return (size_t)Atomic::add_ptr(1, &_next_queue) - 1;

}

// Atomically claims the next available table partition for exclusive

// access by the current thread. Returns the table bucket number where

// the claimed partition starts.

size_t G1StringDedupUnlinkOrOopsDoClosure::claim_table_partition(size_t partition_size) {

  return (size_t)Atomic::add_ptr(partition_size, &_next_bucket) - partition_size;

}