src/hotspot/share/gc/shared/taskTerminator.hpp

rev 60497 : [mq]: 8245721-kbarrett-review2

*** 43,80 ****
   * "Wessam Hassanein. 2016. Understanding and improving JVM GC work
   * stealing at the data center scale. In Proceedings of the 2016 ACM
   * SIGPLAN International Symposium on Memory Management (ISMM 2016). ACM,
   * New York, NY, USA, 46-54. DOI: https://doi.org/10.1145/2926697.2926706"
   *
!  * Instead of a dedicated spin-master, our implementation will let spin-master relinquish
!  * the role before it goes to sleep/wait, allowing newly arrived threads to compete for the role.
!  * The intention of above enhancement is to reduce spin-master's latency on detecting new tasks
!  * for stealing and termination condition.
   */
  class TaskTerminator : public CHeapObj<mtGC> {
!   struct DelayContext {
      uint _yield_count;
      // Number of hard spin loops done since last yield
      uint _hard_spin_count;
!     // Number of iterations in the hard spin loop.
      uint _hard_spin_limit;
  
      DelayContext();
    };
  
    uint _n_threads;
    TaskQueueSetSuper* _queue_set;
  
    DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, 0);
    volatile uint _offered_termination;
    DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile uint));
  
-   void assert_queue_set_empty() const NOT_DEBUG_RETURN;
- 
    Monitor _blocker;
    Thread* _spin_master;
  
    // Prepare for return from offer_termination. Gives up the spin master token
    // and wakes up up to tasks threads waiting on _blocker (the default value
    // means to wake up everyone).
    void prepare_for_return(Thread* this_thread, size_t tasks = SIZE_MAX);
  
--- 43,88 ----
   * "Wessam Hassanein. 2016. Understanding and improving JVM GC work
   * stealing at the data center scale. In Proceedings of the 2016 ACM
   * SIGPLAN International Symposium on Memory Management (ISMM 2016). ACM,
   * New York, NY, USA, 46-54. DOI: https://doi.org/10.1145/2926697.2926706"
   *
!  * Instead of a dedicated spin-master, our implementation will let spin-master
!  * relinquish the role before it goes to sleep/wait, allowing newly arrived
!  * threads to compete for the role.
!  * The intention of above enhancement is to reduce spin-master's latency on
!  * detecting new tasks for stealing and termination condition.
   */
  class TaskTerminator : public CHeapObj<mtGC> {
!   class DelayContext {
      uint _yield_count;
      // Number of hard spin loops done since last yield
      uint _hard_spin_count;
!     // Number of iterations in the current hard spin loop.
      uint _hard_spin_limit;
  
+     void reset_hard_spin_information();
+   public:
      DelayContext();
+ 
+     // Should the caller sleep (wait) or perform a spin step?
+     bool needs_sleep() const;
+     // Perform one delay iteration.
+     void do_step();
    };
  
    uint _n_threads;
    TaskQueueSetSuper* _queue_set;
  
    DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, 0);
    volatile uint _offered_termination;
    DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile uint));
  
    Monitor _blocker;
    Thread* _spin_master;
  
+   void assert_queue_set_empty() const NOT_DEBUG_RETURN;
+ 
    // Prepare for return from offer_termination. Gives up the spin master token
    // and wakes up up to tasks threads waiting on _blocker (the default value
    // means to wake up everyone).
    void prepare_for_return(Thread* this_thread, size_t tasks = SIZE_MAX);
  
*** 82,92 ****
    bool exit_termination(size_t tasks, TerminatorTerminator* terminator);
  
    size_t tasks_in_queue_set() const;
  
    // Perform one iteration of spin-master work.
!   bool do_delay_step(DelayContext& delay_context);
  
    NONCOPYABLE(TaskTerminator);
  
  public:
    TaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set);
--- 90,100 ----
    bool exit_termination(size_t tasks, TerminatorTerminator* terminator);
  
    size_t tasks_in_queue_set() const;
  
    // Perform one iteration of spin-master work.
!   void do_delay_step(DelayContext& delay_context);
  
    NONCOPYABLE(TaskTerminator);
  
  public:
    TaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set);