task.cpp revision 6683:08a2164660fb 
1/*
2 * Copyright (c) 1997, 2014, 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#include "precompiled.hpp"
26#include "memory/allocation.hpp"
27#include "runtime/init.hpp"
28#include "runtime/task.hpp"
29#include "runtime/thread.inline.hpp"
30#include "runtime/timer.hpp"
31
32int PeriodicTask::_num_tasks = 0;
33PeriodicTask* PeriodicTask::_tasks[PeriodicTask::max_tasks];
34#ifndef PRODUCT
35elapsedTimer PeriodicTask::_timer;
36int PeriodicTask::_intervalHistogram[PeriodicTask::max_interval];
37int PeriodicTask::_ticks;
38
39void PeriodicTask::print_intervals() {
40  if (ProfilerCheckIntervals) {
41    for (int i = 0; i < PeriodicTask::max_interval; i++) {
42      int n = _intervalHistogram[i];
43      if (n > 0) tty->print_cr("%3d: %5d (%4.1f%%)", i, n, 100.0 * n / _ticks);
44    }
45  }
46}
47#endif
48
49void PeriodicTask::real_time_tick(int delay_time) {
50#ifndef PRODUCT
51  if (ProfilerCheckIntervals) {
52    _ticks++;
53    _timer.stop();
54    int ms = (int)(_timer.seconds() * 1000.0);
55    _timer.reset();
56    _timer.start();
57    if (ms >= PeriodicTask::max_interval) ms = PeriodicTask::max_interval - 1;
58    _intervalHistogram[ms]++;
59  }
60#endif
61
62  {
63    MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
64    int orig_num_tasks = _num_tasks;
65
66    for(int index = 0; index < _num_tasks; index++) {
67      _tasks[index]->execute_if_pending(delay_time);
68      if (_num_tasks < orig_num_tasks) { // task dis-enrolled itself
69        index--;  // re-do current slot as it has changed
70        orig_num_tasks = _num_tasks;
71      }
72    }
73  }
74}
75
76int PeriodicTask::time_to_wait() {
77  MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ?
78                     NULL : PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
79
80  if (_num_tasks == 0) {
81    return 0; // sleep until shutdown or a task is enrolled
82  }
83
84  int delay = _tasks[0]->time_to_next_interval();
85  for (int index = 1; index < _num_tasks; index++) {
86    delay = MIN2(delay, _tasks[index]->time_to_next_interval());
87  }
88  return delay;
89}
90
91
92PeriodicTask::PeriodicTask(size_t interval_time) :
93  _counter(0), _interval((int) interval_time) {
94  // Sanity check the interval time
95  assert(_interval >= PeriodicTask::min_interval &&
96         _interval %  PeriodicTask::interval_gran == 0,
97              "improper PeriodicTask interval time");
98}
99
100PeriodicTask::~PeriodicTask() {
101  disenroll();
102}
103
104/* enroll could be called from a JavaThread, so we have to check for
105 * safepoint when taking the lock to avoid deadlocking */
106void PeriodicTask::enroll() {
107  MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ?
108                     NULL : PeriodicTask_lock);
109
110  if (_num_tasks == PeriodicTask::max_tasks) {
111    fatal("Overflow in PeriodicTask table");
112  }
113  _tasks[_num_tasks++] = this;
114
115  WatcherThread* thread = WatcherThread::watcher_thread();
116  if (thread) {
117    thread->unpark();
118  } else {
119    WatcherThread::start();
120  }
121}
122
123/* disenroll could be called from a JavaThread, so we have to check for
124 * safepoint when taking the lock to avoid deadlocking */
125void PeriodicTask::disenroll() {
126  MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ?
127                     NULL : PeriodicTask_lock);
128
129  int index;
130  for(index = 0; index < _num_tasks && _tasks[index] != this; index++)
131    ;
132
133  if (index == _num_tasks) {
134    return;
135  }
136
137  _num_tasks--;
138
139  for (; index < _num_tasks; index++) {
140    _tasks[index] = _tasks[index+1];
141  }
142}
143