Mercurial > hg > truffle
annotate src/share/vm/runtime/task.hpp @ 3917:eca1193ca245
4965777: GC changes to support use of discovered field for pending references
Summary: If and when the reference handler thread is able to use the discovered field to link reference objects in its pending list, so will GC. In that case, GC will scan through this field once a reference object has been placed on the pending list, but not scan that field before that stage, as the field is used by the concurrent GC thread to link discovered objects. When ReferenceHandleR thread does not use the discovered field for the purpose of linking the elements in the pending list, as would be the case in older JDKs, the JVM will fall back to the old behaviour of using the next field for that purpose.
Reviewed-by: jcoomes, mchung, stefank
| author | ysr |
|---|---|
| date | Wed, 07 Sep 2011 13:55:42 -0700 |
| parents | f95d63e2154a |
| children | d2a62e0f25eb |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 1972 | 2 * Copyright (c) 1997, 2010, 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 | |
| 1972 | 25 #ifndef SHARE_VM_RUNTIME_TASK_HPP |
| 26 #define SHARE_VM_RUNTIME_TASK_HPP | |
| 27 | |
| 28 #include "utilities/top.hpp" | |
| 29 | |
| 0 | 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 { | |
| 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 size_t _counter; | |
| 53 const size_t _interval; | |
| 54 | |
| 55 static int _num_tasks; | |
| 56 static PeriodicTask* _tasks[PeriodicTask::max_tasks]; | |
| 57 static void real_time_tick(size_t delay_time); | |
| 58 | |
| 59 #ifndef PRODUCT | |
| 60 static elapsedTimer _timer; // measures time between ticks | |
| 61 static int _ticks; // total number of ticks | |
| 62 static int _intervalHistogram[max_interval]; // to check spacing of timer interrupts | |
| 63 public: | |
| 64 static void print_intervals(); | |
| 65 #endif | |
| 66 // Only the WatcherThread can cause us to execute PeriodicTasks | |
| 67 friend class WatcherThread; | |
| 68 public: | |
| 69 PeriodicTask(size_t interval_time); // interval is in milliseconds of elapsed time | |
| 70 ~PeriodicTask(); | |
| 71 | |
| 72 // Tells whether is enrolled | |
| 73 bool is_enrolled() const; | |
| 74 | |
| 75 // Make the task active | |
| 76 // NOTE: this may only be called before the WatcherThread has been started | |
| 77 void enroll(); | |
| 78 | |
| 79 // 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(); | |
| 84 | |
| 85 void execute_if_pending(size_t delay_time) { | |
| 86 _counter += delay_time; | |
| 87 if (_counter >= _interval) { | |
| 88 _counter = 0; | |
| 89 task(); | |
| 90 } | |
| 91 } | |
| 92 | |
| 93 // Returns how long (time in milliseconds) before the next time we should | |
| 94 // execute this task. | |
| 95 size_t 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 // This assumes that periodic tasks aren't entering the system | |
| 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 | |
| 118 // The task to perform at each period | |
| 119 virtual void task() = 0; | |
| 120 }; | |
| 1972 | 121 |
| 122 #endif // SHARE_VM_RUNTIME_TASK_HPP |