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 /*

  * Copyright (c) 2002, 2010, 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

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP

 #include "memory/allocation.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,

     flat_profiler         = 5,

     system_dictionary     = 6,

     class_loader_data     = 7,

     management            = 8,

     jvmti                 = 9,

     code_cache            = 10

   };

  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:

   JavaThread* _java_thread;

   VMThread* _vm_thread;

  public:

   ThreadRootsTask(JavaThread* root) : _java_thread(root), _vm_thread(NULL) {}

   ThreadRootsTask(VMThread* root) : _java_thread(NULL), _vm_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

 // CardTableExtension::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* _gen;

   HeapWord* _gen_top;

   uint _stripe_number;

   uint _stripe_total;

  public:

   OldToYoungRootsTask(PSOldGen *gen,

                       HeapWord* gen_top,

                       uint stripe_number,

                       uint stripe_total) :

     _gen(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_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP