/*

 * Copyright (c) 2002, 2019, 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.

 *

 */

#ifndef SHARE_GC_PARALLEL_PSTASKS_HPP

#define SHARE_GC_PARALLEL_PSTASKS_HPP

#include "utilities/growableArray.hpp"

//

// psTasks.hpp is a collection of GCTasks used by the

// parallelScavenge collector.

//

class GCTask;

class OopClosure;

class OopStack;

class ObjectStartArray;

class ParallelTaskTerminator;

class MutableSpace;

class PSOldGen;

class Thread;

class VMThread;

//

// ScavengeRootsTask

//

// This task scans all the roots of a given type.

//

//

class ScavengeRootsTask : public GCTask {

 public:

  enum RootType {

    universe              = 1,

    jni_handles           = 2,

    threads               = 3,

    object_synchronizer   = 4,

    system_dictionary     = 5,

    class_loader_data     = 6,

    management            = 7,

    jvmti                 = 8,

    code_cache            = 9

  };

 private:

  RootType _root_type;

 public:

  ScavengeRootsTask(RootType value) : _root_type(value) {}

  char* name() { return (char *)"scavenge-roots-task"; }

  virtual void do_it(GCTaskManager* manager, uint which);

};

//

// ThreadRootsTask

//

// This task scans the roots of a single thread. This task

// enables scanning of thread roots in parallel.

//

class ThreadRootsTask : public GCTask {

 private:

  Thread* _thread;

 public:

  ThreadRootsTask(Thread* root) : _thread(root) {}

  char* name() { return (char *)"thread-roots-task"; }

  virtual void do_it(GCTaskManager* manager, uint which);

};

//

// StealTask

//

// This task is used to distribute work to idle threads.

//

class StealTask : public GCTask {

 private:

   ParallelTaskTerminator* const _terminator;

 public:

  char* name() { return (char *)"steal-task"; }

  StealTask(ParallelTaskTerminator* t);

  ParallelTaskTerminator* terminator() { return _terminator; }

  virtual void do_it(GCTaskManager* manager, uint which);

};

//

// OldToYoungRootsTask

//

// This task is used to scan old to young roots in parallel

//

// A GC thread executing this tasks divides the generation (old gen)

// into slices and takes a stripe in the slice as its part of the

// work.

//

//      +===============+        slice 0

//      |  stripe 0     |

//      +---------------+

//      |  stripe 1     |

//      +---------------+

//      |  stripe 2     |

//      +---------------+

//      |  stripe 3     |

//      +===============+        slice 1

//      |  stripe 0     |

//      +---------------+

//      |  stripe 1     |

//      +---------------+

//      |  stripe 2     |

//      +---------------+

//      |  stripe 3     |

//      +===============+        slice 2

//      ...

//

// A task is created for each stripe.  In this case there are 4 tasks

// created.  A GC thread first works on its stripe within slice 0

// and then moves to its stripe in the next slice until all stripes

// exceed the top of the generation.  Note that having fewer GC threads

// than stripes works because all the tasks are executed so all stripes

// will be covered.  In this example if 4 tasks have been created to cover

// all the stripes and there are only 3 threads, one of the threads will

// get the tasks with the 4th stripe.  However, there is a dependence in

// PSCardTable::scavenge_contents_parallel() on the number

// of tasks created.  In scavenge_contents_parallel the distance

// to the next stripe is calculated based on the number of tasks.

// If the stripe width is ssize, a task's next stripe is at

// ssize * number_of_tasks (= slice_stride).  In this case after

// finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1

// by adding slice_stride to the start of stripe 0 in slice 0 to get

// to the start of stride 0 in slice 1.

class OldToYoungRootsTask : public GCTask {

 private:

  PSOldGen* _old_gen;

  HeapWord* _gen_top;

  uint _stripe_number;

  uint _stripe_total;

 public:

  OldToYoungRootsTask(PSOldGen *old_gen,

                      HeapWord* gen_top,

                      uint stripe_number,

                      uint stripe_total) :

    _old_gen(old_gen),

    _gen_top(gen_top),

    _stripe_number(stripe_number),

    _stripe_total(stripe_total) { }

  char* name() { return (char *)"old-to-young-roots-task"; }

  virtual void do_it(GCTaskManager* manager, uint which);

};

#endif // SHARE_GC_PARALLEL_PSTASKS_HPP