Mercurial > hg > truffle
annotate src/share/vm/runtime/task.hpp @ 1768:6ee479178066
6979444: add command line option to print command line flags descriptions
Summary: Implementation of a nonproduct boolean flag XX:PrintFlagsWithComments
Reviewed-by: kamg, dholmes, dsamersoff
author | ikrylov |
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date | Tue, 31 Aug 2010 03:14:00 -0700 |
parents | c18cbe5936b8 |
children | f95d63e2154a |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
25 // A PeriodicTask has the sole purpose of executing its task | |
26 // function with regular intervals. | |
27 // Usage: | |
28 // PeriodicTask pf(10); | |
29 // pf.enroll(); | |
30 // ... | |
31 // pf.disenroll(); | |
32 | |
33 class PeriodicTask: public CHeapObj { | |
34 public: | |
35 // Useful constants. | |
36 // The interval constants are used to ensure the declared interval | |
37 // is appropriate; it must be between min_interval and max_interval, | |
38 // and have a granularity of interval_gran (all in millis). | |
39 enum { max_tasks = 10, // Max number of periodic tasks in system | |
40 interval_gran = 10, | |
41 min_interval = 10, | |
42 max_interval = 10000 }; | |
43 | |
44 static int num_tasks() { return _num_tasks; } | |
45 | |
46 private: | |
47 size_t _counter; | |
48 const size_t _interval; | |
49 | |
50 static int _num_tasks; | |
51 static PeriodicTask* _tasks[PeriodicTask::max_tasks]; | |
52 static void real_time_tick(size_t delay_time); | |
53 | |
54 #ifndef PRODUCT | |
55 static elapsedTimer _timer; // measures time between ticks | |
56 static int _ticks; // total number of ticks | |
57 static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts | |
58 public: | |
59 static void print_intervals(); | |
60 #endif | |
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 // Tells whether is enrolled | |
68 bool is_enrolled() const; | |
69 | |
70 // Make the task active | |
71 // NOTE: this may only be called before the WatcherThread has been started | |
72 void enroll(); | |
73 | |
74 // Make the task deactive | |
75 // NOTE: this may only be called either while the WatcherThread is | |
76 // inactive or by a task from within its task() method. One-shot or | |
77 // several-shot tasks may be implemented this way. | |
78 void disenroll(); | |
79 | |
80 void execute_if_pending(size_t delay_time) { | |
81 _counter += delay_time; | |
82 if (_counter >= _interval) { | |
83 _counter = 0; | |
84 task(); | |
85 } | |
86 } | |
87 | |
88 // Returns how long (time in milliseconds) before the next time we should | |
89 // execute this task. | |
90 size_t time_to_next_interval() const { | |
91 assert(_interval > _counter, "task counter greater than interval?"); | |
92 return _interval - _counter; | |
93 } | |
94 | |
95 // Calculate when the next periodic task will fire. | |
96 // Called by the WatcherThread's run method. | |
97 // This assumes that periodic tasks aren't entering the system | |
98 // dynamically, except for during startup. | |
99 static size_t time_to_wait() { | |
100 if (_num_tasks == 0) { | |
101 // Don't wait any more; shut down the thread since we don't | |
102 // currently support dynamic enrollment. | |
103 return 0; | |
104 } | |
105 | |
106 size_t delay = _tasks[0]->time_to_next_interval(); | |
107 for (int index = 1; index < _num_tasks; index++) { | |
108 delay = MIN2(delay, _tasks[index]->time_to_next_interval()); | |
109 } | |
110 return delay; | |
111 } | |
112 | |
113 // The task to perform at each period | |
114 virtual void task() = 0; | |
115 }; |