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0
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1 /*
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2 * Copyright 2003-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 # include "incls/_precompiled.incl"
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26 # include "incls/_lowMemoryDetector.cpp.incl"
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27
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28 LowMemoryDetectorThread* LowMemoryDetector::_detector_thread = NULL;
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29 volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;
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30 volatile jint LowMemoryDetector::_disabled_count = 0;
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31
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32 void LowMemoryDetector::initialize() {
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33 EXCEPTION_MARK;
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34
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35 instanceKlassHandle klass (THREAD, SystemDictionary::thread_klass());
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36 instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
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37
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38 const char thread_name[] = "Low Memory Detector";
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39 Handle string = java_lang_String::create_from_str(thread_name, CHECK);
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40
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41 // Initialize thread_oop to put it into the system threadGroup
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42 Handle thread_group (THREAD, Universe::system_thread_group());
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43 JavaValue result(T_VOID);
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44 JavaCalls::call_special(&result, thread_oop,
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45 klass,
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46 vmSymbolHandles::object_initializer_name(),
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47 vmSymbolHandles::threadgroup_string_void_signature(),
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48 thread_group,
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49 string,
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50 CHECK);
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51
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52 {
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53 MutexLocker mu(Threads_lock);
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54 _detector_thread = new LowMemoryDetectorThread(&low_memory_detector_thread_entry);
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55
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56 // At this point it may be possible that no osthread was created for the
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57 // JavaThread due to lack of memory. We would have to throw an exception
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58 // in that case. However, since this must work and we do not allow
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59 // exceptions anyway, check and abort if this fails.
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60 if (_detector_thread == NULL || _detector_thread->osthread() == NULL) {
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61 vm_exit_during_initialization("java.lang.OutOfMemoryError",
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62 "unable to create new native thread");
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63 }
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64
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65 java_lang_Thread::set_thread(thread_oop(), _detector_thread);
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66 java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
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67 java_lang_Thread::set_daemon(thread_oop());
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68 _detector_thread->set_threadObj(thread_oop());
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69
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70 Threads::add(_detector_thread);
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71 Thread::start(_detector_thread);
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72 }
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73 }
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74
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75 bool LowMemoryDetector::has_pending_requests() {
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76 assert(LowMemory_lock->owned_by_self(), "Must own LowMemory_lock");
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77 bool has_requests = false;
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78 int num_memory_pools = MemoryService::num_memory_pools();
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79 for (int i = 0; i < num_memory_pools; i++) {
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80 MemoryPool* pool = MemoryService::get_memory_pool(i);
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81 SensorInfo* sensor = pool->usage_sensor();
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82 if (sensor != NULL) {
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83 has_requests = has_requests || sensor->has_pending_requests();
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84 }
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85
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86 SensorInfo* gc_sensor = pool->gc_usage_sensor();
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87 if (gc_sensor != NULL) {
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88 has_requests = has_requests || gc_sensor->has_pending_requests();
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89 }
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90 }
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91 return has_requests;
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92 }
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93
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94 void LowMemoryDetector::low_memory_detector_thread_entry(JavaThread* jt, TRAPS) {
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95 while (true) {
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96 bool sensors_changed = false;
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97
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98 {
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99 // _no_safepoint_check_flag is used here as LowMemory_lock is a
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100 // special lock and the VMThread may acquire this lock at safepoint.
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101 // Need state transition ThreadBlockInVM so that this thread
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102 // will be handled by safepoint correctly when this thread is
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103 // notified at a safepoint.
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104
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105 // This ThreadBlockInVM object is not also considered to be
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106 // suspend-equivalent because LowMemoryDetector threads are
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107 // not visible to external suspension.
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108
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109 ThreadBlockInVM tbivm(jt);
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110
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111 MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
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112 while (!(sensors_changed = has_pending_requests())) {
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113 // wait until one of the sensors has pending requests
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114 LowMemory_lock->wait(Mutex::_no_safepoint_check_flag);
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115 }
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116 }
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117
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118 {
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119 ResourceMark rm(THREAD);
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120 HandleMark hm(THREAD);
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121
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122 // No need to hold LowMemory_lock to call out to Java
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123 int num_memory_pools = MemoryService::num_memory_pools();
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124 for (int i = 0; i < num_memory_pools; i++) {
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125 MemoryPool* pool = MemoryService::get_memory_pool(i);
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126 SensorInfo* sensor = pool->usage_sensor();
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127 SensorInfo* gc_sensor = pool->gc_usage_sensor();
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128 if (sensor != NULL && sensor->has_pending_requests()) {
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129 sensor->process_pending_requests(CHECK);
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130 }
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131 if (gc_sensor != NULL && gc_sensor->has_pending_requests()) {
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132 gc_sensor->process_pending_requests(CHECK);
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133 }
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134 }
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135 }
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136 }
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137 }
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138
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139 // This method could be called from any Java threads
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140 // and also VMThread.
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141 void LowMemoryDetector::detect_low_memory() {
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142 MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
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143
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144 bool has_pending_requests = false;
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145 int num_memory_pools = MemoryService::num_memory_pools();
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146 for (int i = 0; i < num_memory_pools; i++) {
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147 MemoryPool* pool = MemoryService::get_memory_pool(i);
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148 SensorInfo* sensor = pool->usage_sensor();
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149 if (sensor != NULL &&
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150 pool->usage_threshold()->is_high_threshold_supported() &&
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151 pool->usage_threshold()->high_threshold() != 0) {
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152 MemoryUsage usage = pool->get_memory_usage();
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153 sensor->set_gauge_sensor_level(usage,
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154 pool->usage_threshold());
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155 has_pending_requests = has_pending_requests || sensor->has_pending_requests();
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156 }
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157 }
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158
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159 if (has_pending_requests) {
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160 LowMemory_lock->notify_all();
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161 }
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162 }
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163
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164 // This method could be called from any Java threads
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165 // and also VMThread.
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166 void LowMemoryDetector::detect_low_memory(MemoryPool* pool) {
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167 SensorInfo* sensor = pool->usage_sensor();
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168 if (sensor == NULL ||
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169 !pool->usage_threshold()->is_high_threshold_supported() ||
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170 pool->usage_threshold()->high_threshold() == 0) {
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171 return;
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172 }
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173
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174 {
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175 MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
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176
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177 MemoryUsage usage = pool->get_memory_usage();
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178 sensor->set_gauge_sensor_level(usage,
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179 pool->usage_threshold());
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180 if (sensor->has_pending_requests()) {
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181 // notify sensor state update
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182 LowMemory_lock->notify_all();
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183 }
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184 }
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185 }
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186
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187 // Only called by VMThread at GC time
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188 void LowMemoryDetector::detect_after_gc_memory(MemoryPool* pool) {
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189 SensorInfo* sensor = pool->gc_usage_sensor();
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190 if (sensor == NULL ||
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191 !pool->gc_usage_threshold()->is_high_threshold_supported() ||
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192 pool->gc_usage_threshold()->high_threshold() == 0) {
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193 return;
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194 }
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195
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196 {
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197 MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
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198
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199 MemoryUsage usage = pool->get_last_collection_usage();
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200 sensor->set_counter_sensor_level(usage, pool->gc_usage_threshold());
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201
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202 if (sensor->has_pending_requests()) {
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203 // notify sensor state update
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204 LowMemory_lock->notify_all();
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205 }
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206 }
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207 }
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208
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209 // recompute enabled flag
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210 void LowMemoryDetector::recompute_enabled_for_collected_pools() {
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211 bool enabled = false;
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212 int num_memory_pools = MemoryService::num_memory_pools();
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213 for (int i=0; i<num_memory_pools; i++) {
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214 MemoryPool* pool = MemoryService::get_memory_pool(i);
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215 if (pool->is_collected_pool() && is_enabled(pool)) {
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216 enabled = true;
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217 break;
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218 }
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219 }
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220 _enabled_for_collected_pools = enabled;
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221 }
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222
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223 SensorInfo::SensorInfo() {
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224 _sensor_obj = NULL;
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225 _sensor_on = false;
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226 _sensor_count = 0;
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227 _pending_trigger_count = 0;
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228 _pending_clear_count = 0;
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229 }
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230
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231 // When this method is used, the memory usage is monitored
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232 // as a gauge attribute. Sensor notifications (trigger or
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233 // clear) is only emitted at the first time it crosses
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234 // a threshold.
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235 //
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236 // High and low thresholds are designed to provide a
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237 // hysteresis mechanism to avoid repeated triggering
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238 // of notifications when the attribute value makes small oscillations
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239 // around the high or low threshold value.
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240 //
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241 // The sensor will be triggered if:
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242 // (1) the usage is crossing above the high threshold and
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243 // the sensor is currently off and no pending
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244 // trigger requests; or
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245 // (2) the usage is crossing above the high threshold and
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246 // the sensor will be off (i.e. sensor is currently on
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247 // and has pending clear requests).
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248 //
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249 // Subsequent crossings of the high threshold value do not cause
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250 // any triggers unless the usage becomes less than the low threshold.
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251 //
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252 // The sensor will be cleared if:
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253 // (1) the usage is crossing below the low threshold and
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254 // the sensor is currently on and no pending
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255 // clear requests; or
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256 // (2) the usage is crossing below the low threshold and
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257 // the sensor will be on (i.e. sensor is currently off
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258 // and has pending trigger requests).
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259 //
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260 // Subsequent crossings of the low threshold value do not cause
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261 // any clears unless the usage becomes greater than or equal
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262 // to the high threshold.
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263 //
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264 // If the current level is between high and low threhsold, no change.
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265 //
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266 void SensorInfo::set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold) {
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267 assert(high_low_threshold->is_high_threshold_supported(), "just checking");
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268
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269 bool is_over_high = high_low_threshold->is_high_threshold_crossed(usage);
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270 bool is_below_low = high_low_threshold->is_low_threshold_crossed(usage);
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271
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272 assert(!(is_over_high && is_below_low), "Can't be both true");
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273
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274 if (is_over_high &&
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275 ((!_sensor_on && _pending_trigger_count == 0) ||
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276 _pending_clear_count > 0)) {
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277 // low memory detected and need to increment the trigger pending count
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278 // if the sensor is off or will be off due to _pending_clear_ > 0
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279 // Request to trigger the sensor
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280 _pending_trigger_count++;
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281 _usage = usage;
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282
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283 if (_pending_clear_count > 0) {
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284 // non-zero pending clear requests indicates that there are
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285 // pending requests to clear this sensor.
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286 // This trigger request needs to clear this clear count
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287 // since the resulting sensor flag should be on.
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288 _pending_clear_count = 0;
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289 }
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290 } else if (is_below_low &&
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291 ((_sensor_on && _pending_clear_count == 0) ||
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292 (_pending_trigger_count > 0 && _pending_clear_count == 0))) {
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293 // memory usage returns below the threshold
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294 // Request to clear the sensor if the sensor is on or will be on due to
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295 // _pending_trigger_count > 0 and also no clear request
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296 _pending_clear_count++;
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297 }
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298 }
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299
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300 // When this method is used, the memory usage is monitored as a
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301 // simple counter attribute. The sensor will be triggered
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302 // whenever the usage is crossing the threshold to keep track
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303 // of the number of times the VM detects such a condition occurs.
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304 //
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305 // High and low thresholds are designed to provide a
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306 // hysteresis mechanism to avoid repeated triggering
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307 // of notifications when the attribute value makes small oscillations
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308 // around the high or low threshold value.
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309 //
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310 // The sensor will be triggered if:
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311 // - the usage is crossing above the high threshold regardless
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312 // of the current sensor state.
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313 //
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314 // The sensor will be cleared if:
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315 // (1) the usage is crossing below the low threshold and
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316 // the sensor is currently on; or
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317 // (2) the usage is crossing below the low threshold and
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318 // the sensor will be on (i.e. sensor is currently off
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319 // and has pending trigger requests).
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320 void SensorInfo::set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold) {
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321 assert(counter_threshold->is_high_threshold_supported(), "just checking");
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322
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323 bool is_over_high = counter_threshold->is_high_threshold_crossed(usage);
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324 bool is_below_low = counter_threshold->is_low_threshold_crossed(usage);
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325
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326 assert(!(is_over_high && is_below_low), "Can't be both true");
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327
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328 if (is_over_high) {
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329 _pending_trigger_count++;
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330 _usage = usage;
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331 _pending_clear_count = 0;
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332 } else if (is_below_low && (_sensor_on || _pending_trigger_count > 0)) {
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333 _pending_clear_count++;
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334 }
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335 }
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336
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337 void SensorInfo::oops_do(OopClosure* f) {
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338 f->do_oop((oop*) &_sensor_obj);
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339 }
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340
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341 void SensorInfo::process_pending_requests(TRAPS) {
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342 if (!has_pending_requests()) {
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343 return;
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344 }
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345
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346 int pending_count = pending_trigger_count();
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347 if (pending_clear_count() > 0) {
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348 clear(pending_count, CHECK);
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349 } else {
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350 trigger(pending_count, CHECK);
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351 }
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352
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353 }
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354
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355 void SensorInfo::trigger(int count, TRAPS) {
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356 assert(count <= _pending_trigger_count, "just checking");
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357
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358 if (_sensor_obj != NULL) {
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359 klassOop k = Management::sun_management_Sensor_klass(CHECK);
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360 instanceKlassHandle sensorKlass (THREAD, k);
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361 Handle sensor_h(THREAD, _sensor_obj);
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362 Handle usage_h = MemoryService::create_MemoryUsage_obj(_usage, CHECK);
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363
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364 JavaValue result(T_VOID);
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365 JavaCallArguments args(sensor_h);
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366 args.push_int((int) count);
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367 args.push_oop(usage_h);
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368
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369 JavaCalls::call_virtual(&result,
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370 sensorKlass,
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371 vmSymbolHandles::trigger_name(),
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372 vmSymbolHandles::trigger_method_signature(),
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373 &args,
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374 CHECK);
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375 }
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376
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377 {
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378 // Holds LowMemory_lock and update the sensor state
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379 MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
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380 _sensor_on = true;
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381 _sensor_count += count;
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382 _pending_trigger_count = _pending_trigger_count - count;
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383 }
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384 }
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385
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386 void SensorInfo::clear(int count, TRAPS) {
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387 if (_sensor_obj != NULL) {
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388 klassOop k = Management::sun_management_Sensor_klass(CHECK);
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389 instanceKlassHandle sensorKlass (THREAD, k);
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390 Handle sensor(THREAD, _sensor_obj);
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391
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392 JavaValue result(T_VOID);
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393 JavaCallArguments args(sensor);
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394 args.push_int((int) count);
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395 JavaCalls::call_virtual(&result,
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396 sensorKlass,
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397 vmSymbolHandles::clear_name(),
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398 vmSymbolHandles::int_void_signature(),
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399 &args,
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400 CHECK);
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401 }
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402
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403 {
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404 // Holds LowMemory_lock and update the sensor state
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405 MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
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406 _sensor_on = false;
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407 _pending_clear_count = 0;
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408 _pending_trigger_count = _pending_trigger_count - count;
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409 }
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410 }
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411
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412 //--------------------------------------------------------------
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413 // Non-product code
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414
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415 #ifndef PRODUCT
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416 void SensorInfo::print() {
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417 tty->print_cr("%s count = %ld pending_triggers = %ld pending_clears = %ld",
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418 (_sensor_on ? "on" : "off"),
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419 _sensor_count, _pending_trigger_count, _pending_clear_count);
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420 }
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421
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422 #endif // PRODUCT
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