Mercurial > hg > truffle
diff src/share/vm/runtime/task.hpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
parents | |
children | 5a76ab815e34 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/runtime/task.hpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,125 @@ +/* + * Copyright 1997-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +// A PeriodicTask has the sole purpose of executing its task +// function with regular intervals. +// Usage: +// PeriodicTask pf(10); +// pf.enroll(); +// ... +// pf.disenroll(); + +class PeriodicTask: public CHeapObj { + public: + // Useful constants. + // The interval constants are used to ensure the declared interval + // is appropriate; it must be between min_interval and max_interval, + // and have a granularity of interval_gran (all in millis). + enum { max_tasks = 10, // Max number of periodic tasks in system + interval_gran = 10, + min_interval = 10, + max_interval = 10000 }; + + static int num_tasks() { return _num_tasks; } + + private: + size_t _counter; + const size_t _interval; + + static int _num_tasks; + static PeriodicTask* _tasks[PeriodicTask::max_tasks]; + static void real_time_tick(size_t delay_time); + +#ifndef PRODUCT + static elapsedTimer _timer; // measures time between ticks + static int _ticks; // total number of ticks + static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts + public: + static void print_intervals(); +#endif + // Only the WatcherThread can cause us to execute PeriodicTasks + friend class WatcherThread; + public: + PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time + ~PeriodicTask(); + + // Tells whether is enrolled + bool is_enrolled() const; + + // Make the task active + // NOTE: this may only be called before the WatcherThread has been started + void enroll(); + + // Make the task deactive + // NOTE: this may only be called either while the WatcherThread is + // inactive or by a task from within its task() method. One-shot or + // several-shot tasks may be implemented this way. + void disenroll(); + + void execute_if_pending(size_t delay_time) { + _counter += delay_time; + if (_counter >= _interval) { + _counter = 0; + task(); + } + } + + // Returns how long (time in milliseconds) before the next time we should + // execute this task. + size_t time_to_next_interval() const { + assert(_interval > _counter, "task counter greater than interval?"); + return _interval - _counter; + } + + // Calculate when the next periodic task will fire. + // Called by the WatcherThread's run method. + // This assumes that periodic tasks aren't entering the system + // dynamically, except for during startup. + static size_t time_to_wait() { + if (_num_tasks == 0) { + // Don't wait any more; shut down the thread since we don't + // currently support dynamic enrollment. + return 0; + } + + size_t delay = _tasks[0]->time_to_next_interval(); + for (int index = 1; index < _num_tasks; index++) { + delay = MIN2(delay, _tasks[index]->time_to_next_interval()); + } + return delay; + } + + // The task to perform at each period + virtual void task() = 0; +}; + +class TimeMillisUpdateTask : public PeriodicTask { + private: + static TimeMillisUpdateTask* _task; + public: + TimeMillisUpdateTask(int interval) : PeriodicTask(interval) {} + void task(); + static void engage(); + static void disengage(); +};