src/hotspot/share/gc/parallel/psTasks.hpp

8224663: Parallel GC: Use WorkGang (5: ScavengeRootsTask)

*** 41,100 ****
  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
-     JVMCI_ONLY(COMMA jvmci = 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:
-   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.
  //
  
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***************
*** 109,181 ****
    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
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