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annotate src/share/vm/services/lowMemoryDetector.hpp @ 1552:c18cbe5936b8
6941466: Oracle rebranding changes for Hotspot repositories
Summary: Change all the Sun copyrights to Oracle copyright
Reviewed-by: ohair
| author | trims |
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| date | Thu, 27 May 2010 19:08:38 -0700 |
| parents | a61af66fc99e |
| children | f95d63e2154a |
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| 0 | 1 /* |
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2 * Copyright (c) 2003, 2007, 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 // Low Memory Detection Support | |
| 26 // Two memory alarms in the JDK (we called them sensors). | |
| 27 // - Heap memory sensor | |
| 28 // - Non-heap memory sensor | |
| 29 // When the VM detects if the memory usage of a memory pool has reached | |
| 30 // or exceeded its threshold, it will trigger the sensor for the type | |
| 31 // of the memory pool (heap or nonheap or both). | |
| 32 // | |
| 33 // If threshold == -1, no low memory detection is supported and | |
| 34 // the threshold value is not allowed to be changed. | |
| 35 // If threshold == 0, no low memory detection is performed for | |
| 36 // that memory pool. The threshold can be set to any non-negative | |
| 37 // value. | |
| 38 // | |
| 39 // The default threshold of the Hotspot memory pools are: | |
| 40 // Eden space -1 | |
| 41 // Survivor space 1 -1 | |
| 42 // Survivor space 2 -1 | |
| 43 // Old generation 0 | |
| 44 // Perm generation 0 | |
| 45 // CodeCache 0 | |
| 46 // | |
| 47 // For heap memory, detection will be performed when GC finishes | |
| 48 // and also in the slow path allocation. | |
| 49 // For Code cache, detection will be performed in the allocation | |
| 50 // and deallocation. | |
| 51 // | |
| 52 // May need to deal with hysteresis effect. | |
| 53 // | |
| 54 | |
| 55 class LowMemoryDetectorThread; | |
| 56 class OopClosure; | |
| 57 class MemoryPool; | |
| 58 | |
| 59 class ThresholdSupport : public CHeapObj { | |
| 60 private: | |
| 61 bool _support_high_threshold; | |
| 62 bool _support_low_threshold; | |
| 63 size_t _high_threshold; | |
| 64 size_t _low_threshold; | |
| 65 public: | |
| 66 ThresholdSupport(bool support_high, bool support_low) { | |
| 67 _support_high_threshold = support_high; | |
| 68 _support_low_threshold = support_low; | |
| 69 _high_threshold = 0; | |
| 70 _low_threshold= 0; | |
| 71 } | |
| 72 | |
| 73 size_t high_threshold() const { return _high_threshold; } | |
| 74 size_t low_threshold() const { return _low_threshold; } | |
| 75 bool is_high_threshold_supported() { return _support_high_threshold; } | |
| 76 bool is_low_threshold_supported() { return _support_low_threshold; } | |
| 77 | |
| 78 bool is_high_threshold_crossed(MemoryUsage usage) { | |
| 79 if (_support_high_threshold && _high_threshold > 0) { | |
| 80 return (usage.used() >= _high_threshold); | |
| 81 } | |
| 82 return false; | |
| 83 } | |
| 84 bool is_low_threshold_crossed(MemoryUsage usage) { | |
| 85 if (_support_low_threshold && _low_threshold > 0) { | |
| 86 return (usage.used() < _low_threshold); | |
| 87 } | |
| 88 return false; | |
| 89 } | |
| 90 | |
| 91 size_t set_high_threshold(size_t new_threshold) { | |
| 92 assert(_support_high_threshold, "can only be set if supported"); | |
| 93 assert(new_threshold >= _low_threshold, "new_threshold must be >= _low_threshold"); | |
| 94 size_t prev = _high_threshold; | |
| 95 _high_threshold = new_threshold; | |
| 96 return prev; | |
| 97 } | |
| 98 | |
| 99 size_t set_low_threshold(size_t new_threshold) { | |
| 100 assert(_support_low_threshold, "can only be set if supported"); | |
| 101 assert(new_threshold <= _high_threshold, "new_threshold must be <= _high_threshold"); | |
| 102 size_t prev = _low_threshold; | |
| 103 _low_threshold = new_threshold; | |
| 104 return prev; | |
| 105 } | |
| 106 }; | |
| 107 | |
| 108 class SensorInfo : public CHeapObj { | |
| 109 private: | |
| 110 instanceOop _sensor_obj; | |
| 111 bool _sensor_on; | |
| 112 size_t _sensor_count; | |
| 113 | |
| 114 // before the actual sensor on flag and sensor count are set | |
| 115 // we maintain the number of pending triggers and clears. | |
| 116 // _pending_trigger_count means the number of pending triggers | |
| 117 // and the sensor count should be incremented by the same number. | |
| 118 | |
| 119 int _pending_trigger_count; | |
| 120 | |
| 121 // _pending_clear_count takes precedence if it's > 0 which | |
| 122 // indicates the resulting sensor will be off | |
| 123 // Sensor trigger requests will reset this clear count to | |
| 124 // indicate the resulting flag should be on. | |
| 125 | |
| 126 int _pending_clear_count; | |
| 127 | |
| 128 MemoryUsage _usage; | |
| 129 | |
| 130 void clear(int count, TRAPS); | |
| 131 void trigger(int count, TRAPS); | |
| 132 public: | |
| 133 SensorInfo(); | |
| 134 void set_sensor(instanceOop sensor) { | |
| 135 assert(_sensor_obj == NULL, "Should be set only once"); | |
| 136 _sensor_obj = sensor; | |
| 137 } | |
| 138 | |
| 139 bool has_pending_requests() { | |
| 140 return (_pending_trigger_count > 0 || _pending_clear_count > 0); | |
| 141 } | |
| 142 | |
| 143 int pending_trigger_count() { return _pending_trigger_count; } | |
| 144 int pending_clear_count() { return _pending_clear_count; } | |
| 145 | |
| 146 // When this method is used, the memory usage is monitored | |
| 147 // as a gauge attribute. High and low thresholds are designed | |
| 148 // to provide a hysteresis mechanism to avoid repeated triggering | |
| 149 // of notifications when the attribute value makes small oscillations | |
| 150 // around the high or low threshold value. | |
| 151 // | |
| 152 // The sensor will be triggered if: | |
| 153 // (1) the usage is crossing above the high threshold and | |
| 154 // the sensor is currently off and no pending | |
| 155 // trigger requests; or | |
| 156 // (2) the usage is crossing above the high threshold and | |
| 157 // the sensor will be off (i.e. sensor is currently on | |
| 158 // and has pending clear requests). | |
| 159 // | |
| 160 // Subsequent crossings of the high threshold value do not cause | |
| 161 // any triggers unless the usage becomes less than the low threshold. | |
| 162 // | |
| 163 // The sensor will be cleared if: | |
| 164 // (1) the usage is crossing below the low threshold and | |
| 165 // the sensor is currently on and no pending | |
| 166 // clear requests; or | |
| 167 // (2) the usage is crossing below the low threshold and | |
| 168 // the sensor will be on (i.e. sensor is currently off | |
| 169 // and has pending trigger requests). | |
| 170 // | |
| 171 // Subsequent crossings of the low threshold value do not cause | |
| 172 // any clears unless the usage becomes greater than or equal | |
| 173 // to the high threshold. | |
| 174 // | |
| 175 // If the current level is between high and low threhsold, no change. | |
| 176 // | |
| 177 void set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold); | |
| 178 | |
| 179 // When this method is used, the memory usage is monitored as a | |
| 180 // simple counter attribute. The sensor will be triggered | |
| 181 // whenever the usage is crossing the threshold to keep track | |
| 182 // of the number of times the VM detects such a condition occurs. | |
| 183 // | |
| 184 // The sensor will be triggered if: | |
| 185 // - the usage is crossing above the high threshold regardless | |
| 186 // of the current sensor state. | |
| 187 // | |
| 188 // The sensor will be cleared if: | |
| 189 // (1) the usage is crossing below the low threshold and | |
| 190 // the sensor is currently on; or | |
| 191 // (2) the usage is crossing below the low threshold and | |
| 192 // the sensor will be on (i.e. sensor is currently off | |
| 193 // and has pending trigger requests). | |
| 194 // | |
| 195 void set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold); | |
| 196 | |
| 197 void process_pending_requests(TRAPS); | |
| 198 void oops_do(OopClosure* f); | |
| 199 | |
| 200 #ifndef PRODUCT | |
| 201 // printing on default output stream; | |
| 202 void print(); | |
| 203 #endif // PRODUCT | |
| 204 }; | |
| 205 | |
| 206 class LowMemoryDetector : public AllStatic { | |
| 207 friend class LowMemoryDetectorDisabler; | |
| 208 private: | |
| 209 // true if any collected heap has low memory detection enabled | |
| 210 static volatile bool _enabled_for_collected_pools; | |
| 211 // > 0 if temporary disabed | |
| 212 static volatile jint _disabled_count; | |
| 213 | |
| 214 static LowMemoryDetectorThread* _detector_thread; | |
| 215 static void low_memory_detector_thread_entry(JavaThread* thread, TRAPS); | |
| 216 static void check_memory_usage(); | |
| 217 static bool has_pending_requests(); | |
| 218 static bool temporary_disabled() { return _disabled_count > 0; } | |
| 219 static void disable() { Atomic::inc(&_disabled_count); } | |
| 220 static void enable() { Atomic::dec(&_disabled_count); } | |
| 221 | |
| 222 public: | |
| 223 static void initialize(); | |
| 224 static void detect_low_memory(); | |
| 225 static void detect_low_memory(MemoryPool* pool); | |
| 226 static void detect_after_gc_memory(MemoryPool* pool); | |
| 227 | |
| 228 static bool is_enabled(MemoryPool* pool) { | |
| 229 // low memory detection is enabled for collected memory pools | |
| 230 // iff one of the collected memory pool has a sensor and the | |
| 231 // threshold set non-zero | |
| 232 if (pool->usage_sensor() == NULL) { | |
| 233 return false; | |
| 234 } else { | |
| 235 ThresholdSupport* threshold_support = pool->usage_threshold(); | |
| 236 return (threshold_support->is_high_threshold_supported() ? | |
| 237 (threshold_support->high_threshold() > 0) : false); | |
| 238 } | |
| 239 } | |
| 240 | |
| 241 // indicates if low memory detection is enabled for any collected | |
| 242 // memory pools | |
| 243 static inline bool is_enabled_for_collected_pools() { | |
| 244 return !temporary_disabled() && _enabled_for_collected_pools; | |
| 245 } | |
| 246 | |
| 247 // recompute enabled flag | |
| 248 static void recompute_enabled_for_collected_pools(); | |
| 249 | |
| 250 // low memory detection for collected memory pools. | |
| 251 static inline void detect_low_memory_for_collected_pools() { | |
| 252 // no-op if low memory detection not enabled | |
| 253 if (!is_enabled_for_collected_pools()) { | |
| 254 return; | |
| 255 } | |
| 256 int num_memory_pools = MemoryService::num_memory_pools(); | |
| 257 for (int i=0; i<num_memory_pools; i++) { | |
| 258 MemoryPool* pool = MemoryService::get_memory_pool(i); | |
| 259 | |
| 260 // if low memory detection is enabled then check if the | |
| 261 // current used exceeds the high threshold | |
| 262 if (pool->is_collected_pool() && is_enabled(pool)) { | |
| 263 size_t used = pool->used_in_bytes(); | |
| 264 size_t high = pool->usage_threshold()->high_threshold(); | |
| 265 if (used > high) { | |
| 266 detect_low_memory(pool); | |
| 267 } | |
| 268 } | |
| 269 } | |
| 270 } | |
| 271 | |
| 272 }; | |
| 273 | |
| 274 class LowMemoryDetectorDisabler: public StackObj { | |
| 275 public: | |
| 276 LowMemoryDetectorDisabler() | |
| 277 { | |
| 278 LowMemoryDetector::disable(); | |
| 279 } | |
| 280 ~LowMemoryDetectorDisabler() | |
| 281 { | |
| 282 assert(LowMemoryDetector::temporary_disabled(), "should be disabled!"); | |
| 283 LowMemoryDetector::enable(); | |
| 284 } | |
| 285 }; |