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Java example source code file (vmThread.hpp)

This example Java source code file (vmThread.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

cheapobj, cldtooopclosure, medium, mediumpriority, monitor, namedthread, perfcounter, priorities, product_return, returns, share_vm_runtime_vmthread_hpp, vm_operation, vmoperationqueue, vmthread

The vmThread.hpp Java example source code

/*
 * Copyright (c) 1998, 2012, 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_RUNTIME_VMTHREAD_HPP
#define SHARE_VM_RUNTIME_VMTHREAD_HPP

#include "runtime/perfData.hpp"
#include "runtime/thread.inline.hpp"
#include "runtime/vm_operations.hpp"

//
// Prioritized queue of VM operations.
//
// Encapsulates both queue management and
// and priority policy
//
class VMOperationQueue : public CHeapObj<mtInternal> {
 private:
  enum Priorities {
     SafepointPriority, // Highest priority (operation executed at a safepoint)
     MediumPriority,    // Medium priority
     nof_priorities
  };

  // We maintain a doubled linked list, with explicit count.
  int           _queue_length[nof_priorities];
  int           _queue_counter;
  VM_Operation* _queue       [nof_priorities];
  // we also allow the vmThread to register the ops it has drained so we
  // can scan them from oops_do
  VM_Operation* _drain_list;

  // Double-linked non-empty list insert.
  void insert(VM_Operation* q,VM_Operation* n);
  void unlink(VM_Operation* q);

  // Basic queue manipulation
  bool queue_empty                (int prio);
  void queue_add_front            (int prio, VM_Operation *op);
  void queue_add_back             (int prio, VM_Operation *op);
  VM_Operation* queue_remove_front(int prio);
  void queue_oops_do(int queue, OopClosure* f);
  void drain_list_oops_do(OopClosure* f);
  VM_Operation* queue_drain(int prio);
  // lock-free query: may return the wrong answer but must not break
  bool queue_peek(int prio) { return _queue_length[prio] > 0; }

 public:
  VMOperationQueue();

  // Highlevel operations. Encapsulates policy
  bool add(VM_Operation *op);
  VM_Operation* remove_next();                        // Returns next or null
  VM_Operation* remove_next_at_safepoint_priority()   { return queue_remove_front(SafepointPriority); }
  VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); }
  void set_drain_list(VM_Operation* list) { _drain_list = list; }
  bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); }

  // GC support
  void oops_do(OopClosure* f);

  void verify_queue(int prio) PRODUCT_RETURN;
};


//
// A single VMThread (the primordial thread) spawns all other threads
// and is itself used by other threads to offload heavy vm operations
// like scavenge, garbage_collect etc.
//

class VMThread: public NamedThread {
 private:
  static ThreadPriority _current_priority;

  static bool _should_terminate;
  static bool _terminated;
  static Monitor * _terminate_lock;
  static PerfCounter* _perf_accumulated_vm_operation_time;

  void evaluate_operation(VM_Operation* op);
 public:
  // Constructor
  VMThread();

  // Tester
  bool is_VM_thread() const                      { return true; }
  bool is_GC_thread() const                      { return true; }

  // The ever running loop for the VMThread
  void loop();

  // Called to stop the VM thread
  static void wait_for_vm_thread_exit();
  static bool should_terminate()                  { return _should_terminate; }
  static bool is_terminated()                     { return _terminated == true; }

  // Execution of vm operation
  static void execute(VM_Operation* op);

  // Returns the current vm operation if any.
  static VM_Operation* vm_operation()             { return _cur_vm_operation;   }

  // Returns the single instance of VMThread.
  static VMThread* vm_thread()                    { return _vm_thread; }

  // GC support
  void oops_do(OopClosure* f, CLDToOopClosure* cld_f, CodeBlobClosure* cf);

  // Debugging
  void print_on(outputStream* st) const;
  void print() const                              { print_on(tty); }
  void verify();

  // Performance measurement
  static PerfCounter* perf_accumulated_vm_operation_time()               { return _perf_accumulated_vm_operation_time; }

  // Entry for starting vm thread
  virtual void run();

  // Creations/Destructions
  static void create();
  static void destroy();

 private:
  // VM_Operation support
  static VM_Operation*     _cur_vm_operation;   // Current VM operation
  static VMOperationQueue* _vm_queue;           // Queue (w/ policy) of VM operations

  // Pointer to single-instance of VM thread
  static VMThread*     _vm_thread;
};

#endif // SHARE_VM_RUNTIME_VMTHREAD_HPP

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