--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/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();
+};