/*

 * Copyright (c) 2017, 2019, Red Hat, Inc. All rights reserved.

 *

 * 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/shared/stringdedup/stringDedup.inline.hpp"

#include "gc/shared/workgroup.hpp"

#include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"

#include "gc/shenandoah/shenandoahHeap.inline.hpp"

#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"

#include "gc/shenandoah/shenandoahStringDedup.hpp"

#include "gc/shenandoah/shenandoahStrDedupQueue.hpp"

#include "gc/shenandoah/shenandoahTimingTracker.hpp"

#include "gc/shenandoah/shenandoahUtils.hpp"

#include "runtime/thread.hpp"

void ShenandoahStringDedup::initialize() {

  assert(UseShenandoahGC, "String deduplication available with Shenandoah GC");

  StringDedup::initialize_impl<ShenandoahStrDedupQueue, StringDedupStat>();

}

/* Enqueue candidates for deduplication.

 * The method should only be called by GC worker threads during marking phases.

 */

void ShenandoahStringDedup::enqueue_candidate(oop java_string) {

  assert(Thread::current()->is_Worker_thread(),

        "Only from a GC worker thread");

  if (java_string->age() <= StringDeduplicationAgeThreshold) {

    const markWord mark = java_string->mark();

    // Having/had displaced header, too risk to deal with them, skip

    if (mark == markWord::INFLATING() || mark.has_displaced_mark_helper()) {

      return;

    }

    // Increase string age and enqueue it when it rearches age threshold

    markWord new_mark = mark.incr_age();

    if (mark == java_string->cas_set_mark(new_mark, mark)) {

      if (mark.age() == StringDeduplicationAgeThreshold) {

        StringDedupQueue::push(ShenandoahWorkerSession::worker_id(), java_string);

      }

    }

  }

}

// Deduplicate a string, return true if it is deduplicated.

void ShenandoahStringDedup::deduplicate(oop java_string) {

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

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

  StringDedupTable::deduplicate(java_string, &dummy);

}

void ShenandoahStringDedup::parallel_oops_do(BoolObjectClosure* is_alive, OopClosure* cl, uint worker_id) {

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

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

  StringDedupUnlinkOrOopsDoClosure sd_cl(is_alive, cl);

  if (ShenandoahGCPhase::is_root_work_phase()) {

    ShenandoahWorkerTimings* worker_times = ShenandoahHeap::heap()->phase_timings()->worker_times();

    {

      ShenandoahWorkerTimingsTracker x(worker_times, ShenandoahPhaseTimings::StringDedupQueueRoots, worker_id);

      StringDedupQueue::unlink_or_oops_do(&sd_cl);

    }

    {

      ShenandoahWorkerTimingsTracker x(worker_times, ShenandoahPhaseTimings::StringDedupTableRoots, worker_id);

      StringDedupTable::unlink_or_oops_do(&sd_cl, worker_id);

    }

  } else {

    StringDedupQueue::unlink_or_oops_do(&sd_cl);

    StringDedupTable::unlink_or_oops_do(&sd_cl, worker_id);

  }

}

void ShenandoahStringDedup::oops_do_slow(OopClosure* cl) {

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

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

  AlwaysTrueClosure always_true;

  StringDedupUnlinkOrOopsDoClosure sd_cl(&always_true, cl);

  StringDedupQueue::unlink_or_oops_do(&sd_cl);

  StringDedupTable::unlink_or_oops_do(&sd_cl, 0);

}

class ShenandoahIsMarkedNextClosure : public BoolObjectClosure {

private:

  ShenandoahMarkingContext* const _mark_context;

public:

  ShenandoahIsMarkedNextClosure() : _mark_context(ShenandoahHeap::heap()->marking_context()) { }

  bool do_object_b(oop obj) {

    return _mark_context->is_marked(obj);

  }

};

//

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

// and table.

//

class ShenandoahStringDedupUnlinkOrOopsDoTask : public AbstractGangTask {

private:

  StringDedupUnlinkOrOopsDoClosure _cl;

public:

  ShenandoahStringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,

                                  OopClosure* keep_alive,

                                  bool allow_resize_and_rehash) :

    AbstractGangTask("StringDedupUnlinkOrOopsDoTask"),

    _cl(is_alive, keep_alive) {

      StringDedup::gc_prologue(allow_resize_and_rehash);

  }

  ~ShenandoahStringDedupUnlinkOrOopsDoTask() {

    StringDedup::gc_epilogue();

  }

  virtual void work(uint worker_id) {

    StringDedupQueue::unlink_or_oops_do(&_cl);

    StringDedupTable::unlink_or_oops_do(&_cl, worker_id);

  }

};

void ShenandoahStringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive,

                                      OopClosure* keep_alive,

                                      bool allow_resize_and_rehash) {

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

  ShenandoahStringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash);

  ShenandoahHeap* heap = ShenandoahHeap::heap();

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

}