1 /* 2 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_RUNTIME_TASK_HPP 26 #define SHARE_VM_RUNTIME_TASK_HPP 27 28 #include "utilities/top.hpp" 29 30 // A PeriodicTask has the sole purpose of executing its task 31 // function with regular intervals. 32 // Usage: 33 // PeriodicTask pf(10); 34 // pf.enroll(); 35 // ... 36 // pf.disenroll(); 37 38 class PeriodicTask: public CHeapObj<mtInternal> { 39 public: 40 // Useful constants. 41 // The interval constants are used to ensure the declared interval 42 // is appropriate; it must be between min_interval and max_interval, 43 // and have a granularity of interval_gran (all in millis). 44 enum { max_tasks = 10, // Max number of periodic tasks in system 45 interval_gran = 10, 46 min_interval = 10, 47 max_interval = 10000 }; 48 49 static int num_tasks() { return _num_tasks; } 50 51 private: 52 int _counter; 53 const int _interval; 54 55 static int _num_tasks; 56 static PeriodicTask* _tasks[PeriodicTask::max_tasks]; 57 // Can only be called by the WatcherThread 58 static void real_time_tick(int delay_time); 59 60 #ifndef PRODUCT 61 static elapsedTimer _timer; // measures time between ticks 62 static int _ticks; // total number of ticks 63 static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts 64 public: 65 static void print_intervals(); 66 #endif 67 // Only the WatcherThread can cause us to execute PeriodicTasks 68 friend class WatcherThread; 69 public: 70 PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time 71 ~PeriodicTask(); 72 73 // Make the task active 74 // For dynamic enrollment at the time T, the task will execute somewhere 75 // between T and T + interval_time. 76 void enroll(); 77 78 // Make the task deactive 79 void disenroll(); 80 81 void execute_if_pending(int delay_time) { 82 // make sure we don't overflow 83 jlong tmp = (jlong) _counter + (jlong) delay_time; 84 85 if (tmp >= (jlong) _interval) { 86 _counter = 0; 87 task(); 88 } else { 89 _counter += delay_time; 90 } 91 } 92 93 // Returns how long (time in milliseconds) before the next time we should 94 // execute this task. 95 int time_to_next_interval() const { 96 assert(_interval > _counter, "task counter greater than interval?"); 97 return _interval - _counter; 98 } 99 100 // Calculate when the next periodic task will fire. 101 // Called by the WatcherThread's run method. 102 // Requires the PeriodicTask_lock. 103 static int time_to_wait(); 104 105 // The task to perform at each period 106 virtual void task() = 0; 107 }; 108 109 #endif // SHARE_VM_RUNTIME_TASK_HPP