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