author | never |
Thu, 08 Jul 2010 14:29:44 -0700 | |
changeset 5924 | dc9d04930c82 |
parent 5547 | f4b087cbb361 |
child 7397 | 5b173b4ca846 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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* |
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*/ |
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// A PeriodicTask has the sole purpose of executing its task |
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// function with regular intervals. |
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// Usage: |
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// PeriodicTask pf(10); |
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// pf.enroll(); |
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// ... |
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// pf.disenroll(); |
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class PeriodicTask: public CHeapObj { |
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public: |
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// Useful constants. |
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// The interval constants are used to ensure the declared interval |
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// is appropriate; it must be between min_interval and max_interval, |
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// and have a granularity of interval_gran (all in millis). |
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enum { max_tasks = 10, // Max number of periodic tasks in system |
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interval_gran = 10, |
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min_interval = 10, |
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max_interval = 10000 }; |
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static int num_tasks() { return _num_tasks; } |
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private: |
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size_t _counter; |
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const size_t _interval; |
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static int _num_tasks; |
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static PeriodicTask* _tasks[PeriodicTask::max_tasks]; |
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static void real_time_tick(size_t delay_time); |
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#ifndef PRODUCT |
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static elapsedTimer _timer; // measures time between ticks |
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static int _ticks; // total number of ticks |
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static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts |
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public: |
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static void print_intervals(); |
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#endif |
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// Only the WatcherThread can cause us to execute PeriodicTasks |
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friend class WatcherThread; |
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public: |
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PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time |
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~PeriodicTask(); |
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// Tells whether is enrolled |
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bool is_enrolled() const; |
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// Make the task active |
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// NOTE: this may only be called before the WatcherThread has been started |
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void enroll(); |
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// Make the task deactive |
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// NOTE: this may only be called either while the WatcherThread is |
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// inactive or by a task from within its task() method. One-shot or |
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// several-shot tasks may be implemented this way. |
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void disenroll(); |
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void execute_if_pending(size_t delay_time) { |
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_counter += delay_time; |
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if (_counter >= _interval) { |
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_counter = 0; |
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task(); |
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} |
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} |
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// Returns how long (time in milliseconds) before the next time we should |
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// execute this task. |
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size_t time_to_next_interval() const { |
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assert(_interval > _counter, "task counter greater than interval?"); |
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return _interval - _counter; |
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} |
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// Calculate when the next periodic task will fire. |
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// Called by the WatcherThread's run method. |
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// This assumes that periodic tasks aren't entering the system |
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// dynamically, except for during startup. |
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static size_t time_to_wait() { |
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if (_num_tasks == 0) { |
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// Don't wait any more; shut down the thread since we don't |
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// currently support dynamic enrollment. |
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return 0; |
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} |
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size_t delay = _tasks[0]->time_to_next_interval(); |
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for (int index = 1; index < _num_tasks; index++) { |
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delay = MIN2(delay, _tasks[index]->time_to_next_interval()); |
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} |
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return delay; |
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} |
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// The task to perform at each period |
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virtual void task() = 0; |
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}; |