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

rev 60302 : [mq]: 8245721-lkorinth-review

*** 1,7 ****
  /*
!  * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
   * Copyright (c) 2020, 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
--- 1,7 ----
  /*
!  * Copyright (c) 2018, 2020, Red Hat, Inc. All rights reserved.
   * Copyright (c) 2020, 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
*** 24,38 ****
   */
  #ifndef SHARE_GC_SHARED_TASKTERMINATOR_HPP
  #define SHARE_GC_SHARED_TASKTERMINATOR_HPP
  
  #include "memory/allocation.hpp"
  #include "runtime/mutex.hpp"
- #include "runtime/thread.hpp"
  
  class TaskQueueSetSuper;
  class TerminatorTerminator;
  
  /*
   * Provides a task termination protocol.
   *
   * This is an enhanced implementation of Google's OWST work stealing task termination
--- 24,39 ----
   */
  #ifndef SHARE_GC_SHARED_TASKTERMINATOR_HPP
  #define SHARE_GC_SHARED_TASKTERMINATOR_HPP
  
  #include "memory/allocation.hpp"
+ #include "memory/padded.hpp"
  #include "runtime/mutex.hpp"
  
  class TaskQueueSetSuper;
  class TerminatorTerminator;
+ class Thread;
  
  /*
   * Provides a task termination protocol.
   *
   * This is an enhanced implementation of Google's OWST work stealing task termination
*** 48,79 ****
   * 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> {
    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;
  
!   void yield();
! 
!   Monitor*    _blocker;
    Thread*     _spin_master;
  
    // If we should exit current termination protocol
    bool exit_termination(size_t tasks, TerminatorTerminator* terminator);
  
    size_t tasks_in_queue_set() const;
  
!   // Perform spin-master task.
!   // Return true if termination condition is detected, otherwise return false
!   bool do_spin_master_work(TerminatorTerminator* terminator);
  
    NONCOPYABLE(TaskTerminator);
  
  public:
    TaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set);
--- 49,92 ----
   * 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);
+ 
    // If we should exit current termination protocol
    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);