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rev 4518 : 8013934: Garbage collection event for CMS has wrong cause for System.gc()
Reviewed-by: brutisso, jwilhelm
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--- old/src/share/vm/gc_implementation/concurrentMarkSweep/vmCMSOperations.cpp
+++ new/src/share/vm/gc_implementation/concurrentMarkSweep/vmCMSOperations.cpp
1 1 /*
2 2 * Copyright (c) 2005, 2011, Oracle and/or its affiliates. All rights reserved.
3 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 4 *
5 5 * This code is free software; you can redistribute it and/or modify it
6 6 * under the terms of the GNU General Public License version 2 only, as
7 7 * published by the Free Software Foundation.
8 8 *
9 9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 12 * version 2 for more details (a copy is included in the LICENSE file that
13 13 * accompanied this code).
14 14 *
15 15 * You should have received a copy of the GNU General Public License version
16 16 * 2 along with this work; if not, write to the Free Software Foundation,
17 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 18 *
19 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 20 * or visit www.oracle.com if you need additional information or have any
21 21 * questions.
22 22 *
23 23 */
24 24
25 25 #include "precompiled.hpp"
26 26 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
27 27 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
28 28 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
29 29 #include "gc_implementation/shared/gcTimer.hpp"
30 30 #include "gc_implementation/shared/gcTraceTime.hpp"
31 31 #include "gc_implementation/shared/isGCActiveMark.hpp"
32 32 #include "memory/gcLocker.inline.hpp"
33 33 #include "runtime/interfaceSupport.hpp"
34 34 #include "runtime/os.hpp"
35 35 #include "utilities/dtrace.hpp"
36 36
37 37
38 38 #ifndef USDT2
39 39 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
40 40 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
41 41
42 42 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
43 43 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
44 44 #endif /* !USDT2 */
45 45
46 46 //////////////////////////////////////////////////////////
47 47 // Methods in abstract class VM_CMS_Operation
48 48 //////////////////////////////////////////////////////////
49 49 void VM_CMS_Operation::acquire_pending_list_lock() {
50 50 // The caller may block while communicating
51 51 // with the SLT thread in order to acquire/release the PLL.
52 52 ConcurrentMarkSweepThread::slt()->
53 53 manipulatePLL(SurrogateLockerThread::acquirePLL);
54 54 }
55 55
56 56 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
57 57 // The caller may block while communicating
58 58 // with the SLT thread in order to acquire/release the PLL.
59 59 ConcurrentMarkSweepThread::slt()->
60 60 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
61 61 }
62 62
63 63 void VM_CMS_Operation::verify_before_gc() {
64 64 if (VerifyBeforeGC &&
65 65 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
66 66 GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm);
67 67 HandleMark hm;
68 68 FreelistLocker x(_collector);
69 69 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
70 70 Universe::heap()->prepare_for_verify();
71 71 Universe::verify();
72 72 }
73 73 }
74 74
75 75 void VM_CMS_Operation::verify_after_gc() {
76 76 if (VerifyAfterGC &&
77 77 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
78 78 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm);
79 79 HandleMark hm;
80 80 FreelistLocker x(_collector);
81 81 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
82 82 Universe::verify();
83 83 }
84 84 }
85 85
86 86 bool VM_CMS_Operation::lost_race() const {
87 87 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
88 88 // We lost a race to a foreground collection
89 89 // -- there's nothing to do
90 90 return true;
91 91 }
92 92 assert(CMSCollector::abstract_state() == legal_state(),
93 93 "Inconsistent collector state?");
94 94 return false;
95 95 }
96 96
97 97 bool VM_CMS_Operation::doit_prologue() {
98 98 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
99 99 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
100 100 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
101 101 "Possible deadlock");
102 102
103 103 if (needs_pll()) {
104 104 acquire_pending_list_lock();
105 105 }
106 106 // Get the Heap_lock after the pending_list_lock.
107 107 Heap_lock->lock();
108 108 if (lost_race()) {
109 109 assert(_prologue_succeeded == false, "Initialized in c'tor");
110 110 Heap_lock->unlock();
111 111 if (needs_pll()) {
112 112 release_and_notify_pending_list_lock();
113 113 }
114 114 } else {
115 115 _prologue_succeeded = true;
116 116 }
117 117 return _prologue_succeeded;
118 118 }
119 119
120 120 void VM_CMS_Operation::doit_epilogue() {
121 121 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
122 122 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
123 123 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
124 124 "Possible deadlock");
125 125
126 126 // Release the Heap_lock first.
127 127 Heap_lock->unlock();
128 128 if (needs_pll()) {
129 129 release_and_notify_pending_list_lock();
130 130 }
131 131 }
132 132
133 133 //////////////////////////////////////////////////////////
134 134 // Methods in class VM_CMS_Initial_Mark
135 135 //////////////////////////////////////////////////////////
136 136 void VM_CMS_Initial_Mark::doit() {
137 137 if (lost_race()) {
138 138 // Nothing to do.
139 139 return;
140 140 }
141 141 #ifndef USDT2
142 142 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
143 143 #else /* USDT2 */
144 144 HS_PRIVATE_CMS_INITMARK_BEGIN(
145 145 );
146 146 #endif /* USDT2 */
147 147
148 148 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark", os::elapsed_counter());
149 149
150 150 GenCollectedHeap* gch = GenCollectedHeap::heap();
151 151 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
152 152
153 153 VM_CMS_Operation::verify_before_gc();
154 154
155 155 IsGCActiveMark x; // stop-world GC active
156 156 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
157 157
158 158 VM_CMS_Operation::verify_after_gc();
159 159
160 160 _collector->_gc_timer_cm->register_gc_pause_end(os::elapsed_counter());
161 161
162 162 #ifndef USDT2
163 163 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
164 164 #else /* USDT2 */
165 165 HS_PRIVATE_CMS_INITMARK_END(
166 166 );
167 167 #endif /* USDT2 */
168 168 }
169 169
170 170 //////////////////////////////////////////////////////////
171 171 // Methods in class VM_CMS_Final_Remark_Operation
172 172 //////////////////////////////////////////////////////////
173 173 void VM_CMS_Final_Remark::doit() {
174 174 if (lost_race()) {
175 175 // Nothing to do.
176 176 return;
177 177 }
178 178 #ifndef USDT2
179 179 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
180 180 #else /* USDT2 */
181 181 HS_PRIVATE_CMS_REMARK_BEGIN(
182 182 );
183 183 #endif /* USDT2 */
184 184
185 185 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark", os::elapsed_counter());
186 186
187 187 GenCollectedHeap* gch = GenCollectedHeap::heap();
188 188 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
189 189
190 190 VM_CMS_Operation::verify_before_gc();
191 191
192 192 IsGCActiveMark x; // stop-world GC active
193 193 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
194 194
195 195 VM_CMS_Operation::verify_after_gc();
196 196
197 197 _collector->save_heap_summary();
198 198 _collector->_gc_timer_cm->register_gc_pause_end(os::elapsed_counter());
199 199
200 200 #ifndef USDT2
201 201 HS_DTRACE_PROBE(hs_private, cms__remark__end);
202 202 #else /* USDT2 */
203 203 HS_PRIVATE_CMS_REMARK_END(
204 204 );
205 205 #endif /* USDT2 */
206 206 }
207 207
208 208 // VM operation to invoke a concurrent collection of a
209 209 // GenCollectedHeap heap.
210 210 void VM_GenCollectFullConcurrent::doit() {
211 211 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
212 212 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
213 213
214 214 GenCollectedHeap* gch = GenCollectedHeap::heap();
215 215 if (_gc_count_before == gch->total_collections()) {
216 216 // The "full" of do_full_collection call below "forces"
217 217 // a collection; the second arg, 0, below ensures that
218 218 // only the young gen is collected. XXX In the future,
219 219 // we'll probably need to have something in this interface
220 220 // to say do this only if we are sure we will not bail
221 221 // out to a full collection in this attempt, but that's
222 222 // for the future.
223 223 assert(SafepointSynchronize::is_at_safepoint(),
224 224 "We can only be executing this arm of if at a safepoint");
225 225 GCCauseSetter gccs(gch, _gc_cause);
226 226 gch->do_full_collection(gch->must_clear_all_soft_refs(),
227 227 0 /* collect only youngest gen */);
228 228 } // Else no need for a foreground young gc
229 229 assert((_gc_count_before < gch->total_collections()) ||
230 230 (GC_locker::is_active() /* gc may have been skipped */
231 231 && (_gc_count_before == gch->total_collections())),
232 232 "total_collections() should be monotonically increasing");
233 233
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234 234 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
235 235 assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
236 236 if (gch->total_full_collections() == _full_gc_count_before) {
237 237 // Disable iCMS until the full collection is done, and
238 238 // remember that we did so.
239 239 CMSCollector::disable_icms();
240 240 _disabled_icms = true;
241 241 // In case CMS thread was in icms_wait(), wake it up.
242 242 CMSCollector::start_icms();
243 243 // Nudge the CMS thread to start a concurrent collection.
244 - CMSCollector::request_full_gc(_full_gc_count_before);
244 + CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
245 245 } else {
246 246 assert(_full_gc_count_before < gch->total_full_collections(), "Error");
247 247 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
248 248 }
249 249 }
250 250
251 251 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
252 252 Thread* thr = Thread::current();
253 253 assert(thr != NULL, "Unexpected tid");
254 254 if (!thr->is_Java_thread()) {
255 255 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
256 256 GenCollectedHeap* gch = GenCollectedHeap::heap();
257 257 if (_gc_count_before != gch->total_collections()) {
258 258 // No need to do a young gc, we'll just nudge the CMS thread
259 259 // in the doit() method above, to be executed soon.
260 260 assert(_gc_count_before < gch->total_collections(),
261 261 "total_collections() should be monotnically increasing");
262 262 return false; // no need for foreground young gc
263 263 }
264 264 }
265 265 return true; // may still need foreground young gc
266 266 }
267 267
268 268
269 269 void VM_GenCollectFullConcurrent::doit_epilogue() {
270 270 Thread* thr = Thread::current();
271 271 assert(thr->is_Java_thread(), "just checking");
272 272 JavaThread* jt = (JavaThread*)thr;
273 273 // Release the Heap_lock first.
274 274 Heap_lock->unlock();
275 275 release_and_notify_pending_list_lock();
276 276
277 277 // It is fine to test whether completed collections has
278 278 // exceeded our request count without locking because
279 279 // the completion count is monotonically increasing;
280 280 // this will break for very long-running apps when the
281 281 // count overflows and wraps around. XXX fix me !!!
282 282 // e.g. at the rate of 1 full gc per ms, this could
283 283 // overflow in about 1000 years.
284 284 GenCollectedHeap* gch = GenCollectedHeap::heap();
285 285 if (_gc_cause != GCCause::_gc_locker &&
286 286 gch->total_full_collections_completed() <= _full_gc_count_before) {
287 287 // maybe we should change the condition to test _gc_cause ==
288 288 // GCCause::_java_lang_system_gc, instead of
289 289 // _gc_cause != GCCause::_gc_locker
290 290 assert(_gc_cause == GCCause::_java_lang_system_gc,
291 291 "the only way to get here if this was a System.gc()-induced GC");
292 292 assert(ExplicitGCInvokesConcurrent, "Error");
293 293 // Now, wait for witnessing concurrent gc cycle to complete,
294 294 // but do so in native mode, because we want to lock the
295 295 // FullGCEvent_lock, which may be needed by the VM thread
296 296 // or by the CMS thread, so we do not want to be suspended
297 297 // while holding that lock.
298 298 ThreadToNativeFromVM native(jt);
299 299 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
300 300 // Either a concurrent or a stop-world full gc is sufficient
301 301 // witness to our request.
302 302 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
303 303 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
304 304 }
305 305 }
306 306 // Enable iCMS back if we disabled it earlier.
307 307 if (_disabled_icms) {
308 308 CMSCollector::enable_icms();
309 309 }
310 310 }
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