1 /*
2 * Copyright (c) 2003, 2019, 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/handles.inline.hpp"
31 #include "runtime/interfaceSupport.inline.hpp"
32 #include "runtime/java.hpp"
33 #include "runtime/javaCalls.hpp"
34 #include "runtime/mutex.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "services/lowMemoryDetector.hpp"
37 #include "services/management.hpp"
38
39 volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;
40 volatile jint LowMemoryDetector::_disabled_count = 0;
41
42 bool LowMemoryDetector::has_pending_requests() {
43 assert(Service_lock->owned_by_self(), "Must own Service_lock");
44 bool has_requests = false;
45 int num_memory_pools = MemoryService::num_memory_pools();
46 for (int i = 0; i < num_memory_pools; i++) {
47 MemoryPool* pool = MemoryService::get_memory_pool(i);
48 SensorInfo* sensor = pool->usage_sensor();
49 if (sensor != NULL) {
50 has_requests = has_requests || sensor->has_pending_requests();
51 }
52
53 SensorInfo* gc_sensor = pool->gc_usage_sensor();
54 if (gc_sensor != NULL) {
55 has_requests = has_requests || gc_sensor->has_pending_requests();
56 }
57 }
58 return has_requests;
59 }
60
61 void LowMemoryDetector::process_sensor_changes(TRAPS) {
62 ResourceMark rm(THREAD);
63 HandleMark hm(THREAD);
64
65 // No need to hold Service_lock to call out to Java
66 int num_memory_pools = MemoryService::num_memory_pools();
67 for (int i = 0; i < num_memory_pools; i++) {
68 MemoryPool* pool = MemoryService::get_memory_pool(i);
69 SensorInfo* sensor = pool->usage_sensor();
70 SensorInfo* gc_sensor = pool->gc_usage_sensor();
71 if (sensor != NULL && sensor->has_pending_requests()) {
72 sensor->process_pending_requests(CHECK);
73 }
74 if (gc_sensor != NULL && gc_sensor->has_pending_requests()) {
75 gc_sensor->process_pending_requests(CHECK);
76 }
77 }
78 }
79
80 // This method could be called from any Java threads
81 // and also VMThread.
82 void LowMemoryDetector::detect_low_memory() {
83 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
84
85 bool has_pending_requests = false;
86 int num_memory_pools = MemoryService::num_memory_pools();
87 for (int i = 0; i < num_memory_pools; i++) {
88 MemoryPool* pool = MemoryService::get_memory_pool(i);
89 SensorInfo* sensor = pool->usage_sensor();
90 if (sensor != NULL &&
91 pool->usage_threshold()->is_high_threshold_supported() &&
92 pool->usage_threshold()->high_threshold() != 0) {
93 MemoryUsage usage = pool->get_memory_usage();
94 sensor->set_gauge_sensor_level(usage,
95 pool->usage_threshold());
96 has_pending_requests = has_pending_requests || sensor->has_pending_requests();
97 }
98 }
99
100 if (has_pending_requests) {
101 Service_lock->notify_all();
102 }
103 }
104
105 // This method could be called from any Java threads
106 // and also VMThread.
107 void LowMemoryDetector::detect_low_memory(MemoryPool* pool) {
108 SensorInfo* sensor = pool->usage_sensor();
109 if (sensor == NULL ||
110 !pool->usage_threshold()->is_high_threshold_supported() ||
111 pool->usage_threshold()->high_threshold() == 0) {
112 return;
113 }
114
115 {
116 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
117
118 MemoryUsage usage = pool->get_memory_usage();
119 sensor->set_gauge_sensor_level(usage,
120 pool->usage_threshold());
121 if (sensor->has_pending_requests()) {
122 // notify sensor state update
123 Service_lock->notify_all();
124 }
125 }
126 }
127
128 // Only called by VMThread at GC time
129 void LowMemoryDetector::detect_after_gc_memory(MemoryPool* pool) {
130 SensorInfo* sensor = pool->gc_usage_sensor();
131 if (sensor == NULL ||
132 !pool->gc_usage_threshold()->is_high_threshold_supported() ||
133 pool->gc_usage_threshold()->high_threshold() == 0) {
134 return;
135 }
136
137 {
138 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
139
140 MemoryUsage usage = pool->get_last_collection_usage();
141 sensor->set_counter_sensor_level(usage, pool->gc_usage_threshold());
142
143 if (sensor->has_pending_requests()) {
144 // notify sensor state update
145 Service_lock->notify_all();
146 }
147 }
148 }
149
150 // recompute enabled flag
151 void LowMemoryDetector::recompute_enabled_for_collected_pools() {
152 bool enabled = false;
153 int num_memory_pools = MemoryService::num_memory_pools();
154 for (int i=0; i<num_memory_pools; i++) {
155 MemoryPool* pool = MemoryService::get_memory_pool(i);
156 if (pool->is_collected_pool() && is_enabled(pool)) {
157 enabled = true;
158 break;
159 }
160 }
161 _enabled_for_collected_pools = enabled;
162 }
163
164 SensorInfo::SensorInfo() {
165 _sensor_obj = NULL;
166 _sensor_on = false;
167 _sensor_count = 0;
168 _pending_trigger_count = 0;
169 _pending_clear_count = 0;
170 }
171
172 // When this method is used, the memory usage is monitored
173 // as a gauge attribute. Sensor notifications (trigger or
174 // clear) is only emitted at the first time it crosses
175 // a threshold.
176 //
177 // High and low thresholds are designed to provide a
178 // hysteresis mechanism to avoid repeated triggering
179 // of notifications when the attribute value makes small oscillations
180 // around the high or low threshold value.
181 //
182 // The sensor will be triggered if:
183 // (1) the usage is crossing above the high threshold and
184 // the sensor is currently off and no pending
185 // trigger requests; or
186 // (2) the usage is crossing above the high threshold and
187 // the sensor will be off (i.e. sensor is currently on
188 // and has pending clear requests).
189 //
190 // Subsequent crossings of the high threshold value do not cause
191 // any triggers unless the usage becomes less than the low threshold.
192 //
193 // The sensor will be cleared if:
194 // (1) the usage is crossing below the low threshold and
195 // the sensor is currently on and no pending
196 // clear requests; or
197 // (2) the usage is crossing below the low threshold and
198 // the sensor will be on (i.e. sensor is currently off
199 // and has pending trigger requests).
200 //
201 // Subsequent crossings of the low threshold value do not cause
202 // any clears unless the usage becomes greater than or equal
203 // to the high threshold.
204 //
205 // If the current level is between high and low threshold, no change.
206 //
207 void SensorInfo::set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold) {
208 assert(Service_lock->owned_by_self(), "Must own Service_lock");
209 assert(high_low_threshold->is_high_threshold_supported(), "just checking");
210
211 bool is_over_high = high_low_threshold->is_high_threshold_crossed(usage);
212 bool is_below_low = high_low_threshold->is_low_threshold_crossed(usage);
213
214 assert(!(is_over_high && is_below_low), "Can't be both true");
215
216 if (is_over_high &&
217 ((!_sensor_on && _pending_trigger_count == 0) ||
218 _pending_clear_count > 0)) {
219 // low memory detected and need to increment the trigger pending count
220 // if the sensor is off or will be off due to _pending_clear_ > 0
221 // Request to trigger the sensor
222 _pending_trigger_count++;
223 _usage = usage;
224
225 if (_pending_clear_count > 0) {
226 // non-zero pending clear requests indicates that there are
227 // pending requests to clear this sensor.
228 // This trigger request needs to clear this clear count
229 // since the resulting sensor flag should be on.
230 _pending_clear_count = 0;
231 }
232 } else if (is_below_low &&
233 ((_sensor_on && _pending_clear_count == 0) ||
234 (_pending_trigger_count > 0 && _pending_clear_count == 0))) {
235 // memory usage returns below the threshold
236 // Request to clear the sensor if the sensor is on or will be on due to
237 // _pending_trigger_count > 0 and also no clear request
238 _pending_clear_count++;
239 }
240 }
241
242 // When this method is used, the memory usage is monitored as a
243 // simple counter attribute. The sensor will be triggered
244 // whenever the usage is crossing the threshold to keep track
245 // of the number of times the VM detects such a condition occurs.
246 //
247 // High and low thresholds are designed to provide a
248 // hysteresis mechanism to avoid repeated triggering
249 // of notifications when the attribute value makes small oscillations
250 // around the high or low threshold value.
251 //
252 // The sensor will be triggered if:
253 // - the usage is crossing above the high threshold regardless
254 // of the current sensor state.
255 //
256 // The sensor will be cleared if:
257 // (1) the usage is crossing below the low threshold and
258 // the sensor is currently on; or
259 // (2) the usage is crossing below the low threshold and
260 // the sensor will be on (i.e. sensor is currently off
261 // and has pending trigger requests).
262 void SensorInfo::set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold) {
263 assert(Service_lock->owned_by_self(), "Must own Service_lock");
264 assert(counter_threshold->is_high_threshold_supported(), "just checking");
265
266 bool is_over_high = counter_threshold->is_high_threshold_crossed(usage);
267 bool is_below_low = counter_threshold->is_low_threshold_crossed(usage);
268
269 assert(!(is_over_high && is_below_low), "Can't be both true");
270
271 if (is_over_high) {
272 _pending_trigger_count++;
273 _usage = usage;
274 _pending_clear_count = 0;
275 } else if (is_below_low && (_sensor_on || _pending_trigger_count > 0)) {
276 _pending_clear_count++;
277 }
278 }
279
280 void SensorInfo::oops_do(OopClosure* f) {
281 f->do_oop((oop*) &_sensor_obj);
282 }
283
284 void SensorInfo::process_pending_requests(TRAPS) {
285 int pending_count = pending_trigger_count();
286 if (pending_clear_count() > 0) {
287 clear(pending_count, CHECK);
288 } else {
289 trigger(pending_count, CHECK);
290 }
291
292 }
293
294 void SensorInfo::trigger(int count, TRAPS) {
295 assert(count <= _pending_trigger_count, "just checking");
296 if (_sensor_obj != NULL) {
297 InstanceKlass* sensorKlass = Management::sun_management_Sensor_klass(CHECK);
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 MutexLocker 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 MutexLocker 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 InstanceKlass* sensorKlass = Management::sun_management_Sensor_klass(CHECK);
363 Handle sensor(THREAD, _sensor_obj);
364
365 JavaValue result(T_VOID);
366 JavaCallArguments args(sensor);
367 args.push_int((int) count);
368 JavaCalls::call_virtual(&result,
369 sensorKlass,
370 vmSymbols::clear_name(),
371 vmSymbols::int_void_signature(),
372 &args,
373 CHECK);
374 }
375 }
376
377 //--------------------------------------------------------------
378 // Non-product code
379
380 #ifndef PRODUCT
381 void SensorInfo::print() {
382 tty->print_cr("%s count = " SIZE_FORMAT " pending_triggers = %d pending_clears = %d",
383 (_sensor_on ? "on" : "off"),
384 _sensor_count, _pending_trigger_count, _pending_clear_count);
385 }
386
387 #endif // PRODUCT