alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (workgroup.hpp)

This example Java source code file (workgroup.hpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractgangtask, abstractworkgang, cheapobj, freeidset, gangworker, monitor, not_product, null, ooptaskqueueset, share_vm_utilities_workgroup_hpp, stackobj, subtasksdone, workdata, workgangbarriersync

The workgroup.hpp Java example source code

/*
 * Copyright (c) 2002, 2013, 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
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_UTILITIES_WORKGROUP_HPP
#define SHARE_VM_UTILITIES_WORKGROUP_HPP

#include "runtime/thread.inline.hpp"
#include "utilities/taskqueue.hpp"

// Task class hierarchy:
//   AbstractGangTask
//     AbstractGangTaskWOopQueues
//
// Gang/Group class hierarchy:
//   AbstractWorkGang
//     WorkGang
//       FlexibleWorkGang
//         YieldingFlexibleWorkGang (defined in another file)
//
// Worker class hierarchy:
//   GangWorker (subclass of WorkerThread)
//     YieldingFlexibleGangWorker   (defined in another file)

// Forward declarations of classes defined here

class WorkGang;
class GangWorker;
class YieldingFlexibleGangWorker;
class YieldingFlexibleGangTask;
class WorkData;
class AbstractWorkGang;

// An abstract task to be worked on by a gang.
// You subclass this to supply your own work() method
class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
public:
  // The abstract work method.
  // The argument tells you which member of the gang you are.
  virtual void work(uint worker_id) = 0;

  // This method configures the task for proper termination.
  // Some tasks do not have any requirements on termination
  // and may inherit this method that does nothing.  Some
  // tasks do some coordination on termination and override
  // this method to implement that coordination.
  virtual void set_for_termination(int active_workers) {};

  // Debugging accessor for the name.
  const char* name() const PRODUCT_RETURN_(return NULL;);
  int counter() { return _counter; }
  void set_counter(int value) { _counter = value; }
  int *address_of_counter() { return &_counter; }

  // RTTI
  NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
    return false;
  })

private:
  NOT_PRODUCT(const char* _name;)
  // ??? Should a task have a priority associated with it?
  // ??? Or can the run method adjust priority as needed?
  int _counter;

protected:
  // Constructor and desctructor: only construct subclasses.
  AbstractGangTask(const char* name)
  {
    NOT_PRODUCT(_name = name);
    _counter = 0;
  }
  ~AbstractGangTask() { }

public:
};

class AbstractGangTaskWOopQueues : public AbstractGangTask {
  OopTaskQueueSet*       _queues;
  ParallelTaskTerminator _terminator;
 public:
  AbstractGangTaskWOopQueues(const char* name, OopTaskQueueSet* queues) :
    AbstractGangTask(name), _queues(queues), _terminator(0, _queues) {}
  ParallelTaskTerminator* terminator() { return &_terminator; }
  virtual void set_for_termination(int active_workers) {
    terminator()->reset_for_reuse(active_workers);
  }
  OopTaskQueueSet* queues() { return _queues; }
};


// Class AbstractWorkGang:
// An abstract class representing a gang of workers.
// You subclass this to supply an implementation of run_task().
class AbstractWorkGang: public CHeapObj<mtInternal> {
  // Here's the public interface to this class.
public:
  // Constructor and destructor.
  AbstractWorkGang(const char* name, bool are_GC_task_threads,
                   bool are_ConcurrentGC_threads);
  ~AbstractWorkGang();
  // Run a task, returns when the task is done (or terminated).
  virtual void run_task(AbstractGangTask* task) = 0;
  // Stop and terminate all workers.
  virtual void stop();
  // Return true if more workers should be applied to the task.
  virtual bool needs_more_workers() const { return true; }
public:
  // Debugging.
  const char* name() const;
protected:
  // Initialize only instance data.
  const bool _are_GC_task_threads;
  const bool _are_ConcurrentGC_threads;
  // Printing support.
  const char* _name;
  // The monitor which protects these data,
  // and notifies of changes in it.
  Monitor*  _monitor;
  // The count of the number of workers in the gang.
  uint _total_workers;
  // Whether the workers should terminate.
  bool _terminate;
  // The array of worker threads for this gang.
  // This is only needed for cleaning up.
  GangWorker** _gang_workers;
  // The task for this gang.
  AbstractGangTask* _task;
  // A sequence number for the current task.
  int _sequence_number;
  // The number of started workers.
  uint _started_workers;
  // The number of finished workers.
  uint _finished_workers;
public:
  // Accessors for fields
  Monitor* monitor() const {
    return _monitor;
  }
  uint total_workers() const {
    return _total_workers;
  }
  virtual uint active_workers() const {
    return _total_workers;
  }
  bool terminate() const {
    return _terminate;
  }
  GangWorker** gang_workers() const {
    return _gang_workers;
  }
  AbstractGangTask* task() const {
    return _task;
  }
  int sequence_number() const {
    return _sequence_number;
  }
  uint started_workers() const {
    return _started_workers;
  }
  uint finished_workers() const {
    return _finished_workers;
  }
  bool are_GC_task_threads() const {
    return _are_GC_task_threads;
  }
  bool are_ConcurrentGC_threads() const {
    return _are_ConcurrentGC_threads;
  }
  // Predicates.
  bool is_idle() const {
    return (task() == NULL);
  }
  // Return the Ith gang worker.
  GangWorker* gang_worker(uint i) const;

  void threads_do(ThreadClosure* tc) const;

  // Printing
  void print_worker_threads_on(outputStream *st) const;
  void print_worker_threads() const {
    print_worker_threads_on(tty);
  }

protected:
  friend class GangWorker;
  friend class YieldingFlexibleGangWorker;
  // Note activation and deactivation of workers.
  // These methods should only be called with the mutex held.
  void internal_worker_poll(WorkData* data) const;
  void internal_note_start();
  void internal_note_finish();
};

class WorkData: public StackObj {
  // This would be a struct, but I want accessor methods.
private:
  bool              _terminate;
  AbstractGangTask* _task;
  int               _sequence_number;
public:
  // Constructor and destructor
  WorkData() {
    _terminate       = false;
    _task            = NULL;
    _sequence_number = 0;
  }
  ~WorkData() {
  }
  // Accessors and modifiers
  bool terminate()                       const { return _terminate;  }
  void set_terminate(bool value)               { _terminate = value; }
  AbstractGangTask* task()               const { return _task; }
  void set_task(AbstractGangTask* value)       { _task = value; }
  int sequence_number()                  const { return _sequence_number; }
  void set_sequence_number(int value)          { _sequence_number = value; }

  YieldingFlexibleGangTask* yf_task()    const {
    return (YieldingFlexibleGangTask*)_task;
  }
};

// Class WorkGang:
class WorkGang: public AbstractWorkGang {
public:
  // Constructor
  WorkGang(const char* name, uint workers,
           bool are_GC_task_threads, bool are_ConcurrentGC_threads);
  // Run a task, returns when the task is done (or terminated).
  virtual void run_task(AbstractGangTask* task);
  void run_task(AbstractGangTask* task, uint no_of_parallel_workers);
  // Allocate a worker and return a pointer to it.
  virtual GangWorker* allocate_worker(uint which);
  // Initialize workers in the gang.  Return true if initialization
  // succeeded. The type of the worker can be overridden in a derived
  // class with the appropriate implementation of allocate_worker().
  bool initialize_workers();
};

// Class GangWorker:
//   Several instances of this class run in parallel as workers for a gang.
class GangWorker: public WorkerThread {
public:
  // Constructors and destructor.
  GangWorker(AbstractWorkGang* gang, uint id);

  // The only real method: run a task for the gang.
  virtual void run();
  // Predicate for Thread
  virtual bool is_GC_task_thread() const;
  virtual bool is_ConcurrentGC_thread() const;
  // Printing
  void print_on(outputStream* st) const;
  virtual void print() const { print_on(tty); }
protected:
  AbstractWorkGang* _gang;

  virtual void initialize();
  virtual void loop();

public:
  AbstractWorkGang* gang() const { return _gang; }
};

// Dynamic number of worker threads
//
// This type of work gang is used to run different numbers of
// worker threads at different times.  The
// number of workers run for a task is "_active_workers"
// instead of "_total_workers" in a WorkGang.  The method
// "needs_more_workers()" returns true until "_active_workers"
// have been started and returns false afterwards.  The
// implementation of "needs_more_workers()" in WorkGang always
// returns true so that all workers are started.  The method
// "loop()" in GangWorker was modified to ask "needs_more_workers()"
// in its loop to decide if it should start working on a task.
// A worker in "loop()" waits for notification on the WorkGang
// monitor and execution of each worker as it checks for work
// is serialized via the same monitor.  The "needs_more_workers()"
// call is serialized and additionally the calculation for the
// "part" (effectively the worker id for executing the task) is
// serialized to give each worker a unique "part".  Workers that
// are not needed for this tasks (i.e., "_active_workers" have
// been started before it, continue to wait for work.

class FlexibleWorkGang: public WorkGang {
  // The currently active workers in this gang.
  // This is a number that is dynamically adjusted
  // and checked in the run_task() method at each invocation.
  // As described above _active_workers determines the number
  // of threads started on a task.  It must also be used to
  // determine completion.

 protected:
  uint _active_workers;
 public:
  // Constructor and destructor.
  // Initialize active_workers to a minimum value.  Setting it to
  // the parameter "workers" will initialize it to a maximum
  // value which is not desirable.
  FlexibleWorkGang(const char* name, uint workers,
                   bool are_GC_task_threads,
                   bool  are_ConcurrentGC_threads) :
    WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads),
    _active_workers(UseDynamicNumberOfGCThreads ? 1U : ParallelGCThreads) {}
  // Accessors for fields
  virtual uint active_workers() const { return _active_workers; }
  void set_active_workers(uint v) {
    assert(v <= _total_workers,
           "Trying to set more workers active than there are");
    _active_workers = MIN2(v, _total_workers);
    assert(v != 0, "Trying to set active workers to 0");
    _active_workers = MAX2(1U, _active_workers);
    assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
           "Unless dynamic should use total workers");
  }
  virtual void run_task(AbstractGangTask* task);
  virtual bool needs_more_workers() const {
    return _started_workers < _active_workers;
  }
};

// Work gangs in garbage collectors: 2009-06-10
//
// SharedHeap - work gang for stop-the-world parallel collection.
//   Used by
//     ParNewGeneration
//     CMSParRemarkTask
//     CMSRefProcTaskExecutor
//     G1CollectedHeap
//     G1ParFinalCountTask
// ConcurrentMark
// CMSCollector

// A class that acts as a synchronisation barrier. Workers enter
// the barrier and must wait until all other workers have entered
// before any of them may leave.

class WorkGangBarrierSync : public StackObj {
protected:
  Monitor _monitor;
  uint     _n_workers;
  uint     _n_completed;
  bool    _should_reset;

  Monitor* monitor()        { return &_monitor; }
  uint     n_workers()      { return _n_workers; }
  uint     n_completed()    { return _n_completed; }
  bool     should_reset()   { return _should_reset; }

  void     zero_completed() { _n_completed = 0; }
  void     inc_completed()  { _n_completed++; }

  void     set_should_reset(bool v) { _should_reset = v; }

public:
  WorkGangBarrierSync();
  WorkGangBarrierSync(uint n_workers, const char* name);

  // Set the number of workers that will use the barrier.
  // Must be called before any of the workers start running.
  void set_n_workers(uint n_workers);

  // Enter the barrier. A worker that enters the barrier will
  // not be allowed to leave until all other threads have
  // also entered the barrier.
  void enter();
};

// A class to manage claiming of subtasks within a group of tasks.  The
// subtasks will be identified by integer indices, usually elements of an
// enumeration type.

class SubTasksDone: public CHeapObj<mtInternal> {
  uint* _tasks;
  uint _n_tasks;
  // _n_threads is used to determine when a sub task is done.
  // It does not control how many threads will execute the subtask
  // but must be initialized to the number that do execute the task
  // in order to correctly decide when the subtask is done (all the
  // threads working on the task have finished).
  uint _n_threads;
  uint _threads_completed;
#ifdef ASSERT
  volatile uint _claimed;
#endif

  // Set all tasks to unclaimed.
  void clear();

public:
  // Initializes "this" to a state in which there are "n" tasks to be
  // processed, none of the which are originally claimed.  The number of
  // threads doing the tasks is initialized 1.
  SubTasksDone(uint n);

  // True iff the object is in a valid state.
  bool valid();

  // Get/set the number of parallel threads doing the tasks to "t".  Can only
  // be called before tasks start or after they are complete.
  uint n_threads() { return _n_threads; }
  void set_n_threads(uint t);

  // Returns "false" if the task "t" is unclaimed, and ensures that task is
  // claimed.  The task "t" is required to be within the range of "this".
  bool is_task_claimed(uint t);

  // The calling thread asserts that it has attempted to claim all the
  // tasks that it will try to claim.  Every thread in the parallel task
  // must execute this.  (When the last thread does so, the task array is
  // cleared.)
  void all_tasks_completed();

  // Destructor.
  ~SubTasksDone();
};

// As above, but for sequential tasks, i.e. instead of claiming
// sub-tasks from a set (possibly an enumeration), claim sub-tasks
// in sequential order. This is ideal for claiming dynamically
// partitioned tasks (like striding in the parallel remembered
// set scanning). Note that unlike the above class this is
// a stack object - is there any reason for it not to be?

class SequentialSubTasksDone : public StackObj {
protected:
  uint _n_tasks;     // Total number of tasks available.
  uint _n_claimed;   // Number of tasks claimed.
  // _n_threads is used to determine when a sub task is done.
  // See comments on SubTasksDone::_n_threads
  uint _n_threads;   // Total number of parallel threads.
  uint _n_completed; // Number of completed threads.

  void clear();

public:
  SequentialSubTasksDone() {
    clear();
  }
  ~SequentialSubTasksDone() {}

  // True iff the object is in a valid state.
  bool valid();

  // number of tasks
  uint n_tasks() const { return _n_tasks; }

  // Get/set the number of parallel threads doing the tasks to t.
  // Should be called before the task starts but it is safe
  // to call this once a task is running provided that all
  // threads agree on the number of threads.
  uint n_threads() { return _n_threads; }
  void set_n_threads(uint t) { _n_threads = t; }

  // Set the number of tasks to be claimed to t. As above,
  // should be called before the tasks start but it is safe
  // to call this once a task is running provided all threads
  // agree on the number of tasks.
  void set_n_tasks(uint t) { _n_tasks = t; }

  // Returns false if the next task in the sequence is unclaimed,
  // and ensures that it is claimed. Will set t to be the index
  // of the claimed task in the sequence. Will return true if
  // the task cannot be claimed and there are none left to claim.
  bool is_task_claimed(uint& t);

  // The calling thread asserts that it has attempted to claim
  // all the tasks it possibly can in the sequence. Every thread
  // claiming tasks must promise call this. Returns true if this
  // is the last thread to complete so that the thread can perform
  // cleanup if necessary.
  bool all_tasks_completed();
};

// Represents a set of free small integer ids.
class FreeIdSet : public CHeapObj<mtInternal> {
  enum {
    end_of_list = -1,
    claimed = -2
  };

  int _sz;
  Monitor* _mon;

  int* _ids;
  int _hd;
  int _waiters;
  int _claimed;

  static bool _safepoint;
  typedef FreeIdSet* FreeIdSetPtr;
  static const int NSets = 10;
  static FreeIdSetPtr _sets[NSets];
  static bool _stat_init;
  int _index;

public:
  FreeIdSet(int sz, Monitor* mon);
  ~FreeIdSet();

  static void set_safepoint(bool b);

  // Attempt to claim the given id permanently.  Returns "true" iff
  // successful.
  bool claim_perm_id(int i);

  // Returns an unclaimed parallel id (waiting for one to be released if
  // necessary).  Returns "-1" if a GC wakes up a wait for an id.
  int claim_par_id();

  void release_par_id(int id);
};

#endif // SHARE_VM_UTILITIES_WORKGROUP_HPP

Other Java examples (source code examples)

Here is a short list of links related to this Java workgroup.hpp source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.