Mercurial > hg > truffle
comparison src/share/vm/services/lowMemoryDetector.hpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | c18cbe5936b8 |
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1 /* | |
2 * Copyright 2003-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
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 }; |