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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "utilities/growableArray.hpp"
  30 
  31 //
  32 // psTasks.hpp is a collection of GCTasks used by the
  33 // parallelScavenge collector.
  34 //
  35 
  36 class GCTask;
  37 class OopClosure;
  38 class OopStack;
  39 class ObjectStartArray;
  40 class ParallelTaskTerminator;
  41 class MutableSpace;
  42 class PSOldGen;
  43 class Thread;
  44 class VMThread;
  45 
  46 //
  47 // ScavengeRootsTask
  48 //
  49 // This task scans all the roots of a given type.
  50 //
  51 //
  52 
  53 class ScavengeRootsTask : public GCTask {
  54  public:
  55   enum RootType {
  56     universe              = 1,
  57     jni_handles           = 2,
  58     threads               = 3,
  59     object_synchronizer   = 4,
  60     flat_profiler         = 5,
  61     system_dictionary     = 6,
  62     class_loader_data     = 7,
  63     management            = 8,
  64     jvmti                 = 9,
  65     code_cache            = 10
  66   };
  67  private:
  68   RootType _root_type;
  69  public:
  70   ScavengeRootsTask(RootType value) : _root_type(value) {}
  71 
  72   char* name() { return (char *)"scavenge-roots-task"; }
  73 
  74   virtual void do_it(GCTaskManager* manager, uint which);
  75 };
  76 
  77 //
  78 // ThreadRootsTask
  79 //
  80 // This task scans the roots of a single thread. This task
  81 // enables scanning of thread roots in parallel.
  82 //
  83 
  84 class ThreadRootsTask : public GCTask {
  85  private:
  86   JavaThread* _java_thread;
  87   VMThread* _vm_thread;
  88  public:
  89   ThreadRootsTask(JavaThread* root) : _java_thread(root), _vm_thread(NULL) {}
  90   ThreadRootsTask(VMThread* root) : _java_thread(NULL), _vm_thread(root) {}
  91 
  92   char* name() { return (char *)"thread-roots-task"; }
  93 
  94   virtual void do_it(GCTaskManager* manager, uint which);
  95 };
  96 
  97 //
  98 // StealTask
  99 //
 100 // This task is used to distribute work to idle threads.
 101 //
 102 
 103 class StealTask : public GCTask {
 104  private:
 105    ParallelTaskTerminator* const _terminator;
 106  public:
 107   char* name() { return (char *)"steal-task"; }
 108 
 109   StealTask(ParallelTaskTerminator* t);
 110 
 111   ParallelTaskTerminator* terminator() { return _terminator; }
 112 
 113   virtual void do_it(GCTaskManager* manager, uint which);
 114 };
 115 
 116 //
 117 // OldToYoungRootsTask
 118 //
 119 // This task is used to scan old to young roots in parallel
 120 //
 121 // A GC thread executing this tasks divides the generation (old gen)
 122 // into slices and takes a stripe in the slice as its part of the
 123 // work.
 124 //
 125 //      +===============+        slice 0
 126 //      |  stripe 0     |
 127 //      +---------------+
 128 //      |  stripe 1     |
 129 //      +---------------+
 130 //      |  stripe 2     |
 131 //      +---------------+
 132 //      |  stripe 3     |
 133 //      +===============+        slice 1
 134 //      |  stripe 0     |
 135 //      +---------------+
 136 //      |  stripe 1     |
 137 //      +---------------+
 138 //      |  stripe 2     |
 139 //      +---------------+
 140 //      |  stripe 3     |
 141 //      +===============+        slice 2
 142 //      ...
 143 //
 144 // A task is created for each stripe.  In this case there are 4 tasks
 145 // created.  A GC thread first works on its stripe within slice 0
 146 // and then moves to its stripe in the next slice until all stripes
 147 // exceed the top of the generation.  Note that having fewer GC threads
 148 // than stripes works because all the tasks are executed so all stripes
 149 // will be covered.  In this example if 4 tasks have been created to cover
 150 // all the stripes and there are only 3 threads, one of the threads will
 151 // get the tasks with the 4th stripe.  However, there is a dependence in
 152 // CardTableExtension::scavenge_contents_parallel() on the number
 153 // of tasks created.  In scavenge_contents_parallel the distance
 154 // to the next stripe is calculated based on the number of tasks.
 155 // If the stripe width is ssize, a task's next stripe is at
 156 // ssize * number_of_tasks (= slice_stride).  In this case after
 157 // finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1
 158 // by adding slice_stride to the start of stripe 0 in slice 0 to get
 159 // to the start of stride 0 in slice 1.
 160 
 161 class OldToYoungRootsTask : public GCTask {
 162  private:
 163   PSOldGen* _gen;
 164   HeapWord* _gen_top;
 165   uint _stripe_number;
 166   uint _stripe_total;
 167 
 168  public:
 169   OldToYoungRootsTask(PSOldGen *gen,
 170                       HeapWord* gen_top,
 171                       uint stripe_number,
 172                       uint stripe_total) :
 173     _gen(gen),
 174     _gen_top(gen_top),
 175     _stripe_number(stripe_number),
 176     _stripe_total(stripe_total) { }
 177 
 178   char* name() { return (char *)"old-to-young-roots-task"; }
 179 
 180   virtual void do_it(GCTaskManager* manager, uint which);
 181 };
 182 
 183 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSTASKS_HPP