1 /*
2 * Copyright (c) 2003, 2016, 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 "classfile/systemDictionary.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "runtime/interfaceSupport.hpp"
31 #include "runtime/java.hpp"
32 #include "runtime/javaCalls.hpp"
33 #include "runtime/mutex.hpp"
34 #include "runtime/mutexLocker.hpp"
35 #include "services/lowMemoryDetector.hpp"
36 #include "services/management.hpp"
37
38 volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;
39 volatile jint LowMemoryDetector::_disabled_count = 0;
40
41 bool LowMemoryDetector::has_pending_requests() {
42 assert(Service_lock->owned_by_self(), "Must own Service_lock");
43 bool has_requests = false;
44 int num_memory_pools = MemoryService::num_memory_pools();
45 for (int i = 0; i < num_memory_pools; i++) {
46 MemoryPool* pool = MemoryService::get_memory_pool(i);
47 SensorInfo* sensor = pool->usage_sensor();
48 if (sensor != NULL) {
49 has_requests = has_requests || sensor->has_pending_requests();
50 }
51
52 SensorInfo* gc_sensor = pool->gc_usage_sensor();
53 if (gc_sensor != NULL) {
54 has_requests = has_requests || gc_sensor->has_pending_requests();
55 }
56 }
57 return has_requests;
58 }
59
60 void LowMemoryDetector::process_sensor_changes(TRAPS) {
61 ResourceMark rm(THREAD);
62 HandleMark hm(THREAD);
63
64 // No need to hold Service_lock to call out to Java
65 int num_memory_pools = MemoryService::num_memory_pools();
66 for (int i = 0; i < num_memory_pools; i++) {
67 MemoryPool* pool = MemoryService::get_memory_pool(i);
68 SensorInfo* sensor = pool->usage_sensor();
69 SensorInfo* gc_sensor = pool->gc_usage_sensor();
70 if (sensor != NULL && sensor->has_pending_requests()) {
71 sensor->process_pending_requests(CHECK);
72 }
73 if (gc_sensor != NULL && gc_sensor->has_pending_requests()) {
74 gc_sensor->process_pending_requests(CHECK);
75 }
76 }
77 }
78
79 // This method could be called from any Java threads
80 // and also VMThread.
81 void LowMemoryDetector::detect_low_memory() {
82 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
83
84 bool has_pending_requests = false;
85 int num_memory_pools = MemoryService::num_memory_pools();
86 for (int i = 0; i < num_memory_pools; i++) {
87 MemoryPool* pool = MemoryService::get_memory_pool(i);
88 SensorInfo* sensor = pool->usage_sensor();
89 if (sensor != NULL &&
90 pool->usage_threshold()->is_high_threshold_supported() &&
91 pool->usage_threshold()->high_threshold() != 0) {
92 MemoryUsage usage = pool->get_memory_usage();
93 sensor->set_gauge_sensor_level(usage,
94 pool->usage_threshold());
95 has_pending_requests = has_pending_requests || sensor->has_pending_requests();
96 }
97 }
98
99 if (has_pending_requests) {
100 Service_lock->notify_all();
101 }
102 }
103
104 // This method could be called from any Java threads
105 // and also VMThread.
106 void LowMemoryDetector::detect_low_memory(MemoryPool* pool) {
107 SensorInfo* sensor = pool->usage_sensor();
108 if (sensor == NULL ||
109 !pool->usage_threshold()->is_high_threshold_supported() ||
110 pool->usage_threshold()->high_threshold() == 0) {
111 return;
112 }
113
114 {
115 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
116
117 MemoryUsage usage = pool->get_memory_usage();
118 sensor->set_gauge_sensor_level(usage,
119 pool->usage_threshold());
120 if (sensor->has_pending_requests()) {
121 // notify sensor state update
122 Service_lock->notify_all();
123 }
124 }
125 }
126
127 // Only called by VMThread at GC time
128 void LowMemoryDetector::detect_after_gc_memory(MemoryPool* pool) {
129 SensorInfo* sensor = pool->gc_usage_sensor();
130 if (sensor == NULL ||
131 !pool->gc_usage_threshold()->is_high_threshold_supported() ||
132 pool->gc_usage_threshold()->high_threshold() == 0) {
133 return;
134 }
135
136 {
137 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
138
139 MemoryUsage usage = pool->get_last_collection_usage();
140 sensor->set_counter_sensor_level(usage, pool->gc_usage_threshold());
141
142 if (sensor->has_pending_requests()) {
143 // notify sensor state update
144 Service_lock->notify_all();
145 }
146 }
147 }
148
149 // recompute enabled flag
150 void LowMemoryDetector::recompute_enabled_for_collected_pools() {
151 bool enabled = false;
152 int num_memory_pools = MemoryService::num_memory_pools();
153 for (int i=0; i<num_memory_pools; i++) {
154 MemoryPool* pool = MemoryService::get_memory_pool(i);
155 if (pool->is_collected_pool() && is_enabled(pool)) {
156 enabled = true;
157 break;
158 }
159 }
160 _enabled_for_collected_pools = enabled;
161 }
162
163 SensorInfo::SensorInfo() {
164 _sensor_obj = NULL;
165 _sensor_on = false;
166 _sensor_count = 0;
167 _pending_trigger_count = 0;
168 _pending_clear_count = 0;
169 }
170
171 // When this method is used, the memory usage is monitored
172 // as a gauge attribute. Sensor notifications (trigger or
173 // clear) is only emitted at the first time it crosses
174 // a threshold.
175 //
176 // High and low thresholds are designed to provide a
177 // hysteresis mechanism to avoid repeated triggering
178 // of notifications when the attribute value makes small oscillations
179 // around the high or low threshold value.
180 //
181 // The sensor will be triggered if:
182 // (1) the usage is crossing above the high threshold and
183 // the sensor is currently off and no pending
184 // trigger requests; or
185 // (2) the usage is crossing above the high threshold and
186 // the sensor will be off (i.e. sensor is currently on
187 // and has pending clear requests).
188 //
189 // Subsequent crossings of the high threshold value do not cause
190 // any triggers unless the usage becomes less than the low threshold.
191 //
192 // The sensor will be cleared if:
193 // (1) the usage is crossing below the low threshold and
194 // the sensor is currently on and no pending
195 // clear requests; or
196 // (2) the usage is crossing below the low threshold and
197 // the sensor will be on (i.e. sensor is currently off
198 // and has pending trigger requests).
199 //
200 // Subsequent crossings of the low threshold value do not cause
201 // any clears unless the usage becomes greater than or equal
202 // to the high threshold.
203 //
204 // If the current level is between high and low threshold, no change.
205 //
206 void SensorInfo::set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold) {
207 assert(Service_lock->owned_by_self(), "Must own Service_lock");
208 assert(high_low_threshold->is_high_threshold_supported(), "just checking");
209
210 bool is_over_high = high_low_threshold->is_high_threshold_crossed(usage);
211 bool is_below_low = high_low_threshold->is_low_threshold_crossed(usage);
212
213 assert(!(is_over_high && is_below_low), "Can't be both true");
214
215 if (is_over_high &&
216 ((!_sensor_on && _pending_trigger_count == 0) ||
217 _pending_clear_count > 0)) {
218 // low memory detected and need to increment the trigger pending count
219 // if the sensor is off or will be off due to _pending_clear_ > 0
220 // Request to trigger the sensor
221 _pending_trigger_count++;
222 _usage = usage;
223
224 if (_pending_clear_count > 0) {
225 // non-zero pending clear requests indicates that there are
226 // pending requests to clear this sensor.
227 // This trigger request needs to clear this clear count
228 // since the resulting sensor flag should be on.
229 _pending_clear_count = 0;
230 }
231 } else if (is_below_low &&
232 ((_sensor_on && _pending_clear_count == 0) ||
233 (_pending_trigger_count > 0 && _pending_clear_count == 0))) {
234 // memory usage returns below the threshold
235 // Request to clear the sensor if the sensor is on or will be on due to
236 // _pending_trigger_count > 0 and also no clear request
237 _pending_clear_count++;
238 }
239 }
240
241 // When this method is used, the memory usage is monitored as a
242 // simple counter attribute. The sensor will be triggered
243 // whenever the usage is crossing the threshold to keep track
244 // of the number of times the VM detects such a condition occurs.
245 //
246 // High and low thresholds are designed to provide a
247 // hysteresis mechanism to avoid repeated triggering
248 // of notifications when the attribute value makes small oscillations
249 // around the high or low threshold value.
250 //
251 // The sensor will be triggered if:
252 // - the usage is crossing above the high threshold regardless
253 // of the current sensor state.
254 //
255 // The sensor will be cleared if:
256 // (1) the usage is crossing below the low threshold and
257 // the sensor is currently on; or
258 // (2) the usage is crossing below the low threshold and
259 // the sensor will be on (i.e. sensor is currently off
260 // and has pending trigger requests).
261 void SensorInfo::set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold) {
262 assert(Service_lock->owned_by_self(), "Must own Service_lock");
263 assert(counter_threshold->is_high_threshold_supported(), "just checking");
264
265 bool is_over_high = counter_threshold->is_high_threshold_crossed(usage);
266 bool is_below_low = counter_threshold->is_low_threshold_crossed(usage);
267
268 assert(!(is_over_high && is_below_low), "Can't be both true");
269
270 if (is_over_high) {
271 _pending_trigger_count++;
272 _usage = usage;
273 _pending_clear_count = 0;
274 } else if (is_below_low && (_sensor_on || _pending_trigger_count > 0)) {
275 _pending_clear_count++;
276 }
277 }
278
279 void SensorInfo::oops_do(OopClosure* f) {
280 f->do_oop((oop*) &_sensor_obj);
281 }
282
283 void SensorInfo::process_pending_requests(TRAPS) {
284 int pending_count = pending_trigger_count();
285 if (pending_clear_count() > 0) {
286 clear(pending_count, CHECK);
287 } else {
288 trigger(pending_count, CHECK);
289 }
290
291 }
292
293 void SensorInfo::trigger(int count, TRAPS) {
294 assert(count <= _pending_trigger_count, "just checking");
295 if (_sensor_obj != NULL) {
296 Klass* k = Management::sun_management_Sensor_klass(CHECK);
297 instanceKlassHandle sensorKlass (THREAD, k);
298 Handle sensor_h(THREAD, _sensor_obj);
299
300 Symbol* trigger_method_signature;
301
302 JavaValue result(T_VOID);
303 JavaCallArguments args(sensor_h);
304 args.push_int((int) count);
305
306 Handle usage_h = MemoryService::create_MemoryUsage_obj(_usage, THREAD);
307 // call Sensor::trigger(int, MemoryUsage) to send notification to listeners.
308 // when OOME occurs and fails to allocate MemoryUsage object, call
309 // Sensor::trigger(int) instead. The pending request will be processed
310 // but no notification will be sent.
311 if (HAS_PENDING_EXCEPTION) {
312 assert((PENDING_EXCEPTION->is_a(SystemDictionary::OutOfMemoryError_klass())), "we expect only an OOME here");
313 CLEAR_PENDING_EXCEPTION;
314 trigger_method_signature = vmSymbols::int_void_signature();
315 } else {
316 trigger_method_signature = vmSymbols::trigger_method_signature();
317 args.push_oop(usage_h);
318 }
319
320 JavaCalls::call_virtual(&result,
321 sensorKlass,
322 vmSymbols::trigger_name(),
323 trigger_method_signature,
324 &args,
325 THREAD);
326
327 if (HAS_PENDING_EXCEPTION) {
328 // we just clear the OOM pending exception that we might have encountered
329 // in Java's tiggerAction(), and continue with updating the counters since
330 // the Java counters have been updated too.
331 assert((PENDING_EXCEPTION->is_a(SystemDictionary::OutOfMemoryError_klass())), "we expect only an OOME here");
332 CLEAR_PENDING_EXCEPTION;
333 }
334 }
335
336 {
337 // Holds Service_lock and update the sensor state
338 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
339 assert(_pending_trigger_count > 0, "Must have pending trigger");
340 _sensor_on = true;
341 _sensor_count += count;
342 _pending_trigger_count = _pending_trigger_count - count;
343 }
344 }
345
346 void SensorInfo::clear(int count, TRAPS) {
347 {
348 // Holds Service_lock and update the sensor state
349 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
350 if (_pending_clear_count == 0) {
351 // Bail out if we lost a race to set_*_sensor_level() which may have
352 // reactivated the sensor in the meantime because it was triggered again.
353 return;
354 }
355 _sensor_on = false;
356 _sensor_count += count;
357 _pending_clear_count = 0;
358 _pending_trigger_count = _pending_trigger_count - count;
359 }
360
361 if (_sensor_obj != NULL) {
362 Klass* k = Management::sun_management_Sensor_klass(CHECK);
363 instanceKlassHandle sensorKlass (THREAD, k);
364 Handle sensor(THREAD, _sensor_obj);
365
366 JavaValue result(T_VOID);
367 JavaCallArguments args(sensor);
368 args.push_int((int) count);
369 JavaCalls::call_virtual(&result,
370 sensorKlass,
371 vmSymbols::clear_name(),
372 vmSymbols::int_void_signature(),
373 &args,
374 CHECK);
375 }
376 }
377
378 //--------------------------------------------------------------
379 // Non-product code
380
381 #ifndef PRODUCT
382 void SensorInfo::print() {
383 tty->print_cr("%s count = " SIZE_FORMAT " pending_triggers = %d pending_clears = %d",
384 (_sensor_on ? "on" : "off"),
385 _sensor_count, _pending_trigger_count, _pending_clear_count);
386 }
387
388 #endif // PRODUCT