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comparison src/share/vm/runtime/task.hpp @ 6939:c284cf4781f0

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7127792: Add the ability to change an existing PeriodicTask's execution interval Summary: Enables dynamic enrollment / disenrollment from the PeriodicTasks in WatcherThread. Reviewed-by: dholmes, mgronlun
author rbackman
date Thu, 04 Oct 2012 14:55:57 +0200
parents b9a9ed0f8eeb
children
comparison
equal deleted inserted replaced
6938:8940ddc1036f 6939:c284cf4781f0
47 max_interval = 10000 }; 47 max_interval = 10000 };
48 48
49 static int num_tasks() { return _num_tasks; } 49 static int num_tasks() { return _num_tasks; }
50 50
51 private: 51 private:
52 size_t _counter; 52 int _counter;
53 const size_t _interval; 53 const int _interval;
54 54
55 static int _num_tasks; 55 static int _num_tasks;
56 static PeriodicTask* _tasks[PeriodicTask::max_tasks]; 56 static PeriodicTask* _tasks[PeriodicTask::max_tasks];
57 static void real_time_tick(size_t delay_time); 57 static void real_time_tick(int delay_time);
58 58
59 #ifndef PRODUCT 59 #ifndef PRODUCT
60 static elapsedTimer _timer; // measures time between ticks 60 static elapsedTimer _timer; // measures time between ticks
61 static int _ticks; // total number of ticks 61 static int _ticks; // total number of ticks
62 static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts 62 static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts
67 friend class WatcherThread; 67 friend class WatcherThread;
68 public: 68 public:
69 PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time 69 PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time
70 ~PeriodicTask(); 70 ~PeriodicTask();
71 71
72 // Tells whether is enrolled
73 bool is_enrolled() const;
74
75 // Make the task active 72 // Make the task active
76 // NOTE: this may only be called before the WatcherThread has been started 73 // For dynamic enrollment at the time T, the task will execute somewhere
74 // between T and T + interval_time.
77 void enroll(); 75 void enroll();
78 76
79 // Make the task deactive 77 // Make the task deactive
80 // NOTE: this may only be called either while the WatcherThread is
81 // inactive or by a task from within its task() method. One-shot or
82 // several-shot tasks may be implemented this way.
83 void disenroll(); 78 void disenroll();
84 79
85 void execute_if_pending(size_t delay_time) { 80 void execute_if_pending(int delay_time) {
86 _counter += delay_time; 81 // make sure we don't overflow
87 if (_counter >= _interval) { 82 jlong tmp = (jlong) _counter + (jlong) delay_time;
83
84 if (tmp >= (jlong) _interval) {
88 _counter = 0; 85 _counter = 0;
89 task(); 86 task();
87 } else {
88 _counter += delay_time;
90 } 89 }
91 } 90 }
92 91
93 // Returns how long (time in milliseconds) before the next time we should 92 // Returns how long (time in milliseconds) before the next time we should
94 // execute this task. 93 // execute this task.
95 size_t time_to_next_interval() const { 94 int time_to_next_interval() const {
96 assert(_interval > _counter, "task counter greater than interval?"); 95 assert(_interval > _counter, "task counter greater than interval?");
97 return _interval - _counter; 96 return _interval - _counter;
98 } 97 }
99 98
100 // Calculate when the next periodic task will fire. 99 // Calculate when the next periodic task will fire.
101 // Called by the WatcherThread's run method. 100 // Called by the WatcherThread's run method.
102 // This assumes that periodic tasks aren't entering the system 101 static int time_to_wait();
103 // dynamically, except for during startup.
104 static size_t time_to_wait() {
105 if (_num_tasks == 0) {
106 // Don't wait any more; shut down the thread since we don't
107 // currently support dynamic enrollment.
108 return 0;
109 }
110
111 size_t delay = _tasks[0]->time_to_next_interval();
112 for (int index = 1; index < _num_tasks; index++) {
113 delay = MIN2(delay, _tasks[index]->time_to_next_interval());
114 }
115 return delay;
116 }
117 102
118 // The task to perform at each period 103 // The task to perform at each period
119 virtual void task() = 0; 104 virtual void task() = 0;
120 }; 105 };
121 106