1 /*
2 * Copyright (c) 2003, 2015, 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 "oops/oop.inline.hpp"
29 #include "runtime/interfaceSupport.hpp"
30 #include "runtime/java.hpp"
31 #include "runtime/javaCalls.hpp"
32 #include "runtime/mutex.hpp"
33 #include "runtime/mutexLocker.hpp"
34 #include "services/lowMemoryDetector.hpp"
35 #include "services/management.hpp"
36
37 volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;
38 volatile jint LowMemoryDetector::_disabled_count = 0;
39
40 bool LowMemoryDetector::has_pending_requests() {
41 assert(Service_lock->owned_by_self(), "Must own Service_lock");
42 bool has_requests = false;
43 int num_memory_pools = MemoryService::num_memory_pools();
44 for (int i = 0; i < num_memory_pools; i++) {
45 MemoryPool* pool = MemoryService::get_memory_pool(i);
46 SensorInfo* sensor = pool->usage_sensor();
47 if (sensor != NULL) {
48 has_requests = has_requests || sensor->has_pending_requests();
49 }
50
51 SensorInfo* gc_sensor = pool->gc_usage_sensor();
52 if (gc_sensor != NULL) {
53 has_requests = has_requests || gc_sensor->has_pending_requests();
54 }
55 }
56 return has_requests;
57 }
58
59 void LowMemoryDetector::process_sensor_changes(TRAPS) {
60 ResourceMark rm(THREAD);
61 HandleMark hm(THREAD);
62
63 // No need to hold Service_lock to call out to Java
64 int num_memory_pools = MemoryService::num_memory_pools();
65 for (int i = 0; i < num_memory_pools; i++) {
66 MemoryPool* pool = MemoryService::get_memory_pool(i);
67 SensorInfo* sensor = pool->usage_sensor();
68 SensorInfo* gc_sensor = pool->gc_usage_sensor();
69 if (sensor != NULL && sensor->has_pending_requests()) {
70 sensor->process_pending_requests(CHECK);
71 }
72 if (gc_sensor != NULL && gc_sensor->has_pending_requests()) {
73 gc_sensor->process_pending_requests(CHECK);
74 }
75 }
76 }
77
78 // This method could be called from any Java threads
79 // and also VMThread.
80 void LowMemoryDetector::detect_low_memory() {
81 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
82
83 bool has_pending_requests = false;
84 int num_memory_pools = MemoryService::num_memory_pools();
85 for (int i = 0; i < num_memory_pools; i++) {
86 MemoryPool* pool = MemoryService::get_memory_pool(i);
87 SensorInfo* sensor = pool->usage_sensor();
88 if (sensor != NULL &&
89 pool->usage_threshold()->is_high_threshold_supported() &&
90 pool->usage_threshold()->high_threshold() != 0) {
91 MemoryUsage usage = pool->get_memory_usage();
92 sensor->set_gauge_sensor_level(usage,
93 pool->usage_threshold());
94 has_pending_requests = has_pending_requests || sensor->has_pending_requests();
95 }
96 }
97
98 if (has_pending_requests) {
99 Service_lock->notify_all();
100 }
101 }
102
103 // This method could be called from any Java threads
104 // and also VMThread.
105 void LowMemoryDetector::detect_low_memory(MemoryPool* pool) {
106 SensorInfo* sensor = pool->usage_sensor();
107 if (sensor == NULL ||
108 !pool->usage_threshold()->is_high_threshold_supported() ||
109 pool->usage_threshold()->high_threshold() == 0) {
110 return;
111 }
112
113 {
114 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
115
116 MemoryUsage usage = pool->get_memory_usage();
117 sensor->set_gauge_sensor_level(usage,
118 pool->usage_threshold());
119 if (sensor->has_pending_requests()) {
120 // notify sensor state update
121 Service_lock->notify_all();
122 }
123 }
124 }
125
126 // Only called by VMThread at GC time
127 void LowMemoryDetector::detect_after_gc_memory(MemoryPool* pool) {
128 SensorInfo* sensor = pool->gc_usage_sensor();
129 if (sensor == NULL ||
130 !pool->gc_usage_threshold()->is_high_threshold_supported() ||
131 pool->gc_usage_threshold()->high_threshold() == 0) {
132 return;
133 }
134
135 {
136 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
137
138 MemoryUsage usage = pool->get_last_collection_usage();
139 sensor->set_counter_sensor_level(usage, pool->gc_usage_threshold());
140
141 if (sensor->has_pending_requests()) {
142 // notify sensor state update
143 Service_lock->notify_all();
144 }
145 }
146 }
147
148 // recompute enabled flag
149 void LowMemoryDetector::recompute_enabled_for_collected_pools() {
150 bool enabled = false;
151 int num_memory_pools = MemoryService::num_memory_pools();
152 for (int i=0; i<num_memory_pools; i++) {
153 MemoryPool* pool = MemoryService::get_memory_pool(i);
154 if (pool->is_collected_pool() && is_enabled(pool)) {
155 enabled = true;
156 break;
157 }
158 }
159 _enabled_for_collected_pools = enabled;
160 }
161
162 SensorInfo::SensorInfo() {
163 _sensor_obj = NULL;
164 _sensor_on = false;
165 _sensor_count = 0;
166 _pending_trigger_count = 0;
167 _pending_clear_count = 0;
168 }
169
170 // When this method is used, the memory usage is monitored
171 // as a gauge attribute. Sensor notifications (trigger or
172 // clear) is only emitted at the first time it crosses
173 // a threshold.
174 //
175 // High and low thresholds are designed to provide a
176 // hysteresis mechanism to avoid repeated triggering
177 // of notifications when the attribute value makes small oscillations
178 // around the high or low threshold value.
179 //
180 // The sensor will be triggered if:
181 // (1) the usage is crossing above the high threshold and
182 // the sensor is currently off and no pending
183 // trigger requests; or
184 // (2) the usage is crossing above the high threshold and
185 // the sensor will be off (i.e. sensor is currently on
186 // and has pending clear requests).
187 //
188 // Subsequent crossings of the high threshold value do not cause
189 // any triggers unless the usage becomes less than the low threshold.
190 //
191 // The sensor will be cleared if:
192 // (1) the usage is crossing below the low threshold and
193 // the sensor is currently on and no pending
194 // clear requests; or
195 // (2) the usage is crossing below the low threshold and
196 // the sensor will be on (i.e. sensor is currently off
197 // and has pending trigger requests).
198 //
199 // Subsequent crossings of the low threshold value do not cause
200 // any clears unless the usage becomes greater than or equal
201 // to the high threshold.
202 //
203 // If the current level is between high and low threshold, no change.
204 //
205 void SensorInfo::set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold) {
206 assert(Service_lock->owned_by_self(), "Must own Service_lock");
207 assert(high_low_threshold->is_high_threshold_supported(), "just checking");
208
209 bool is_over_high = high_low_threshold->is_high_threshold_crossed(usage);
210 bool is_below_low = high_low_threshold->is_low_threshold_crossed(usage);
211
212 assert(!(is_over_high && is_below_low), "Can't be both true");
213
214 if (is_over_high &&
215 ((!_sensor_on && _pending_trigger_count == 0) ||
216 _pending_clear_count > 0)) {
217 // low memory detected and need to increment the trigger pending count
218 // if the sensor is off or will be off due to _pending_clear_ > 0
219 // Request to trigger the sensor
220 _pending_trigger_count++;
221 _usage = usage;
222
223 if (_pending_clear_count > 0) {
224 // non-zero pending clear requests indicates that there are
225 // pending requests to clear this sensor.
226 // This trigger request needs to clear this clear count
227 // since the resulting sensor flag should be on.
228 _pending_clear_count = 0;
229 }
230 } else if (is_below_low &&
231 ((_sensor_on && _pending_clear_count == 0) ||
232 (_pending_trigger_count > 0 && _pending_clear_count == 0))) {
233 // memory usage returns below the threshold
234 // Request to clear the sensor if the sensor is on or will be on due to
235 // _pending_trigger_count > 0 and also no clear request
236 _pending_clear_count++;
237 }
238 }
239
240 // When this method is used, the memory usage is monitored as a
241 // simple counter attribute. The sensor will be triggered
242 // whenever the usage is crossing the threshold to keep track
243 // of the number of times the VM detects such a condition occurs.
244 //
245 // High and low thresholds are designed to provide a
246 // hysteresis mechanism to avoid repeated triggering
247 // of notifications when the attribute value makes small oscillations
248 // around the high or low threshold value.
249 //
250 // The sensor will be triggered if:
251 // - the usage is crossing above the high threshold regardless
252 // of the current sensor state.
253 //
254 // The sensor will be cleared if:
255 // (1) the usage is crossing below the low threshold and
256 // the sensor is currently on; or
257 // (2) the usage is crossing below the low threshold and
258 // the sensor will be on (i.e. sensor is currently off
259 // and has pending trigger requests).
260 void SensorInfo::set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold) {
261 assert(Service_lock->owned_by_self(), "Must own Service_lock");
262 assert(counter_threshold->is_high_threshold_supported(), "just checking");
263
264 bool is_over_high = counter_threshold->is_high_threshold_crossed(usage);
265 bool is_below_low = counter_threshold->is_low_threshold_crossed(usage);
266
267 assert(!(is_over_high && is_below_low), "Can't be both true");
268
269 if (is_over_high) {
270 _pending_trigger_count++;
271 _usage = usage;
272 _pending_clear_count = 0;
273 } else if (is_below_low && (_sensor_on || _pending_trigger_count > 0)) {
274 _pending_clear_count++;
275 }
276 }
277
278 void SensorInfo::oops_do(OopClosure* f) {
279 f->do_oop((oop*) &_sensor_obj);
280 }
281
282 void SensorInfo::process_pending_requests(TRAPS) {
283 assert(has_pending_requests(), "Must have pending request");
284
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 Klass* k = Management::sun_management_Sensor_klass(CHECK);
298 instanceKlassHandle sensorKlass (THREAD, k);
299 Handle sensor_h(THREAD, _sensor_obj);
300 Handle usage_h = MemoryService::create_MemoryUsage_obj(_usage, CHECK);
301
302 JavaValue result(T_VOID);
303 JavaCallArguments args(sensor_h);
304 args.push_int((int) count);
305 args.push_oop(usage_h);
306
307 JavaCalls::call_virtual(&result,
308 sensorKlass,
309 vmSymbols::trigger_name(),
310 vmSymbols::trigger_method_signature(),
311 &args,
312 CHECK);
313 }
314
315 {
316 // Holds Service_lock and update the sensor state
317 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
318 assert(_pending_trigger_count > 0, "Must have pending trigger");
319 _sensor_on = true;
320 _sensor_count += count;
321 _pending_trigger_count = _pending_trigger_count - count;
322 }
323 }
324
325 void SensorInfo::clear(int count, TRAPS) {
326 {
327 // Holds Service_lock and update the sensor state
328 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
329 if (_pending_clear_count == 0) {
330 // Bail out if we lost a race to set_*_sensor_level() which may have
331 // reactivated the sensor in the meantime because it was triggered again.
332 return;
333 }
334 _sensor_on = false;
335 _sensor_count += count;
336 _pending_clear_count = 0;
337 _pending_trigger_count = _pending_trigger_count - count;
338 }
339
340 if (_sensor_obj != NULL) {
341 Klass* k = Management::sun_management_Sensor_klass(CHECK);
342 instanceKlassHandle sensorKlass (THREAD, k);
343 Handle sensor(THREAD, _sensor_obj);
344
345 JavaValue result(T_VOID);
346 JavaCallArguments args(sensor);
347 args.push_int((int) count);
348 JavaCalls::call_virtual(&result,
349 sensorKlass,
350 vmSymbols::clear_name(),
351 vmSymbols::int_void_signature(),
352 &args,
353 CHECK);
354 }
355 }
356
357 //--------------------------------------------------------------
358 // Non-product code
359
360 #ifndef PRODUCT
361 void SensorInfo::print() {
362 tty->print_cr("%s count = " SIZE_FORMAT " pending_triggers = %d pending_clears = %d",
363 (_sensor_on ? "on" : "off"),
364 _sensor_count, _pending_trigger_count, _pending_clear_count);
365 }
366
367 #endif // PRODUCT