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src/share/vm/runtime/task.hpp@9f4457a14b58 (annotated)

src/share/vm/runtime/task.hpp

Wed, 09 Apr 2008 15:10:22 -0700

author

rasbold

date

Wed, 09 Apr 2008 15:10:22 -0700

changeset 544

9f4457a14b58

parent 496

5a76ab815e34

child 631

d1605aabd0a1

permissions

-rw-r--r--

Merge

duke@435	1	/*
duke@435	2	* Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
duke@435	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435	4	*
duke@435	5	* This code is free software; you can redistribute it and/or modify it
duke@435	6	* under the terms of the GNU General Public License version 2 only, as
duke@435	7	* published by the Free Software Foundation.
duke@435	8	*
duke@435	9	* This code is distributed in the hope that it will be useful, but WITHOUT
duke@435	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435	12	* version 2 for more details (a copy is included in the LICENSE file that
duke@435	13	* accompanied this code).
duke@435	14	*
duke@435	15	* You should have received a copy of the GNU General Public License version
duke@435	16	* 2 along with this work; if not, write to the Free Software Foundation,
duke@435	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435	18	*
duke@435	19	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435	20	* CA 95054 USA or visit www.sun.com if you need additional information or
duke@435	21	* have any questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
duke@435	25	// A PeriodicTask has the sole purpose of executing its task
duke@435	26	// function with regular intervals.
duke@435	27	// Usage:
duke@435	28	// PeriodicTask pf(10);
duke@435	29	// pf.enroll();
duke@435	30	// ...
duke@435	31	// pf.disenroll();
duke@435	32
duke@435	33	class PeriodicTask: public CHeapObj {
duke@435	34	public:
duke@435	35	// Useful constants.
duke@435	36	// The interval constants are used to ensure the declared interval
duke@435	37	// is appropriate; it must be between min_interval and max_interval,
duke@435	38	// and have a granularity of interval_gran (all in millis).
duke@435	39	enum { max_tasks = 10, // Max number of periodic tasks in system
duke@435	40	interval_gran = 10,
duke@435	41	min_interval = 10,
duke@435	42	max_interval = 10000 };
duke@435	43
duke@435	44	static int num_tasks() { return _num_tasks; }
duke@435	45
duke@435	46	private:
duke@435	47	size_t _counter;
duke@435	48	const size_t _interval;
duke@435	49
duke@435	50	static int _num_tasks;
duke@435	51	static PeriodicTask* _tasks[PeriodicTask::max_tasks];
duke@435	52	static void real_time_tick(size_t delay_time);
duke@435	53
duke@435	54	#ifndef PRODUCT
duke@435	55	static elapsedTimer _timer; // measures time between ticks
duke@435	56	static int _ticks; // total number of ticks
duke@435	57	static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts
duke@435	58	public:
duke@435	59	static void print_intervals();
duke@435	60	#endif
duke@435	61	// Only the WatcherThread can cause us to execute PeriodicTasks
duke@435	62	friend class WatcherThread;
duke@435	63	public:
duke@435	64	PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time
duke@435	65	~PeriodicTask();
duke@435	66
duke@435	67	// Tells whether is enrolled
duke@435	68	bool is_enrolled() const;
duke@435	69
duke@435	70	// Make the task active
duke@435	71	// NOTE: this may only be called before the WatcherThread has been started
duke@435	72	void enroll();
duke@435	73
duke@435	74	// Make the task deactive
duke@435	75	// NOTE: this may only be called either while the WatcherThread is
duke@435	76	// inactive or by a task from within its task() method. One-shot or
duke@435	77	// several-shot tasks may be implemented this way.
duke@435	78	void disenroll();
duke@435	79
duke@435	80	void execute_if_pending(size_t delay_time) {
duke@435	81	_counter += delay_time;
duke@435	82	if (_counter >= _interval) {
duke@435	83	_counter = 0;
duke@435	84	task();
duke@435	85	}
duke@435	86	}
duke@435	87
duke@435	88	// Returns how long (time in milliseconds) before the next time we should
duke@435	89	// execute this task.
duke@435	90	size_t time_to_next_interval() const {
duke@435	91	assert(_interval > _counter, "task counter greater than interval?");
duke@435	92	return _interval - _counter;
duke@435	93	}
duke@435	94
duke@435	95	// Calculate when the next periodic task will fire.
duke@435	96	// Called by the WatcherThread's run method.
duke@435	97	// This assumes that periodic tasks aren't entering the system
duke@435	98	// dynamically, except for during startup.
duke@435	99	static size_t time_to_wait() {
duke@435	100	if (_num_tasks == 0) {
duke@435	101	// Don't wait any more; shut down the thread since we don't
duke@435	102	// currently support dynamic enrollment.
duke@435	103	return 0;
duke@435	104	}
duke@435	105
duke@435	106	size_t delay = _tasks[0]->time_to_next_interval();
duke@435	107	for (int index = 1; index < _num_tasks; index++) {
duke@435	108	delay = MIN2(delay, _tasks[index]->time_to_next_interval());
duke@435	109	}
duke@435	110	return delay;
duke@435	111	}
duke@435	112
duke@435	113	// The task to perform at each period
duke@435	114	virtual void task() = 0;
duke@435	115	};