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24
25#ifndef SHARE_RUNTIME_TASK_HPP
26#define SHARE_RUNTIME_TASK_HPP
27
28#include "memory/allocation.hpp"
29#include "runtime/timer.hpp"
30
31// A PeriodicTask has the sole purpose of executing its task
32// function with regular intervals.
33// Usage:
34// PeriodicTask pf(10);
35// pf.enroll();
36// ...
37// pf.disenroll();
38
39class PeriodicTask: public CHeapObj<mtInternal> {
40 public:
41 // Useful constants.
42 // The interval constants are used to ensure the declared interval
43 // is appropriate; it must be between min_interval and max_interval,
44 // and have a granularity of interval_gran (all in millis).
45 enum { max_tasks = 10, // Max number of periodic tasks in system
46 interval_gran = 10,
47 min_interval = 10,
48 max_interval = 10000 };
49
50 static int num_tasks() { return _num_tasks; }
51
52 private:
53 int _counter;
54 const int _interval;
55
56 static int _num_tasks;
57 static PeriodicTask* _tasks[PeriodicTask::max_tasks];
58 // Can only be called by the WatcherThread
59 static void real_time_tick(int delay_time);
60
61 // Only the WatcherThread can cause us to execute PeriodicTasks
62 friend class WatcherThread;
63 public:
64 PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time
65 ~PeriodicTask();
66
67 // Make the task active
68 // For dynamic enrollment at the time T, the task will execute somewhere
69 // between T and T + interval_time.
70 void enroll();
71
72 // Make the task deactive
73 void disenroll();
74
75 void execute_if_pending(int delay_time) {
76 // make sure we don't overflow
77 jlong tmp = (jlong) _counter + (jlong) delay_time;
78
79 if (tmp >= (jlong) _interval) {
80 _counter = 0;
81 task();
82 } else {
83 _counter += delay_time;
84 }
85 }
86
87 // Returns how long (time in milliseconds) before the next time we should
88 // execute this task.
89 int time_to_next_interval() const {
90 assert(_interval > _counter, "task counter greater than interval?");
91 return _interval - _counter;
92 }
93
94 // Calculate when the next periodic task will fire.
95 // Called by the WatcherThread's run method.
96 // Requires the PeriodicTask_lock.
97 static int time_to_wait();
98
99 // The task to perform at each period
100 virtual void task() = 0;
101};
102
103#endif // SHARE_RUNTIME_TASK_HPP
104