1 /*
2 * Copyright (c) 2005, 2013, 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 "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
27 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
28 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
29 #include "gc_implementation/shared/gcTimer.hpp"
30 #include "gc_implementation/shared/gcTraceTime.hpp"
31 #include "gc_implementation/shared/isGCActiveMark.hpp"
32 #include "memory/gcLocker.inline.hpp"
33 #include "runtime/interfaceSupport.hpp"
34 #include "runtime/os.hpp"
35 #include "utilities/dtrace.hpp"
36
37
38 #ifndef USDT2
39 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
40 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
41
42 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
43 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
44 #endif /* !USDT2 */
45
46 //////////////////////////////////////////////////////////
47 // Methods in abstract class VM_CMS_Operation
48 //////////////////////////////////////////////////////////
49 void VM_CMS_Operation::acquire_pending_list_lock() {
50 // The caller may block while communicating
51 // with the SLT thread in order to acquire/release the PLL.
52 ConcurrentMarkSweepThread::slt()->
53 manipulatePLL(SurrogateLockerThread::acquirePLL);
54 }
55
56 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
57 // The caller may block while communicating
58 // with the SLT thread in order to acquire/release the PLL.
59 ConcurrentMarkSweepThread::slt()->
60 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
61 }
62
63 void VM_CMS_Operation::verify_before_gc() {
64 if (VerifyBeforeGC &&
65 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
66 GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm);
67 HandleMark hm;
68 FreelistLocker x(_collector);
69 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
70 Universe::heap()->prepare_for_verify();
71 Universe::verify();
72 }
73 }
74
75 void VM_CMS_Operation::verify_after_gc() {
76 if (VerifyAfterGC &&
77 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
78 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm);
79 HandleMark hm;
80 FreelistLocker x(_collector);
81 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
82 Universe::verify();
83 }
84 }
85
86 bool VM_CMS_Operation::lost_race() const {
87 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
88 // We lost a race to a foreground collection
89 // -- there's nothing to do
90 return true;
91 }
92 assert(CMSCollector::abstract_state() == legal_state(),
93 "Inconsistent collector state?");
94 return false;
95 }
96
97 bool VM_CMS_Operation::doit_prologue() {
98 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
99 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
100 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
101 "Possible deadlock");
102
103 if (needs_pll()) {
104 acquire_pending_list_lock();
105 }
106 // Get the Heap_lock after the pending_list_lock.
107 Heap_lock->lock();
108 if (lost_race()) {
109 assert(_prologue_succeeded == false, "Initialized in c'tor");
110 Heap_lock->unlock();
111 if (needs_pll()) {
112 release_and_notify_pending_list_lock();
113 }
114 } else {
115 _prologue_succeeded = true;
116 }
117 return _prologue_succeeded;
118 }
119
120 void VM_CMS_Operation::doit_epilogue() {
121 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
122 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
123 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
124 "Possible deadlock");
125
126 // Release the Heap_lock first.
127 Heap_lock->unlock();
128 if (needs_pll()) {
129 release_and_notify_pending_list_lock();
130 }
131 }
132
133 //////////////////////////////////////////////////////////
134 // Methods in class VM_CMS_Initial_Mark
135 //////////////////////////////////////////////////////////
136 void VM_CMS_Initial_Mark::doit() {
137 if (lost_race()) {
138 // Nothing to do.
139 return;
140 }
141 #ifndef USDT2
142 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
143 #else /* USDT2 */
144 HS_PRIVATE_CMS_INITMARK_BEGIN();
145 #endif /* USDT2 */
146
147 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");
148
149 GenCollectedHeap* gch = GenCollectedHeap::heap();
150 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
151
152 VM_CMS_Operation::verify_before_gc();
153
154 IsGCActiveMark x; // stop-world GC active
155 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
156
157 VM_CMS_Operation::verify_after_gc();
158
159 _collector->_gc_timer_cm->register_gc_pause_end();
160
161 #ifndef USDT2
162 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
163 #else /* USDT2 */
164 HS_PRIVATE_CMS_INITMARK_END();
165 #endif /* USDT2 */
166 }
167
168 //////////////////////////////////////////////////////////
169 // Methods in class VM_CMS_Final_Remark_Operation
170 //////////////////////////////////////////////////////////
171 void VM_CMS_Final_Remark::doit() {
172 if (lost_race()) {
173 // Nothing to do.
174 return;
175 }
176 #ifndef USDT2
177 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
178 #else /* USDT2 */
179 HS_PRIVATE_CMS_REMARK_BEGIN();
180 #endif /* USDT2 */
181
182 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");
183
184 GenCollectedHeap* gch = GenCollectedHeap::heap();
185 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
186
187 VM_CMS_Operation::verify_before_gc();
188
189 IsGCActiveMark x; // stop-world GC active
190 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
191
192 VM_CMS_Operation::verify_after_gc();
193
194 _collector->save_heap_summary();
195 _collector->_gc_timer_cm->register_gc_pause_end();
196
197 #ifndef USDT2
198 HS_DTRACE_PROBE(hs_private, cms__remark__end);
199 #else /* USDT2 */
200 HS_PRIVATE_CMS_REMARK_END();
201 #endif /* USDT2 */
202 }
203
204 // VM operation to invoke a concurrent collection of a
205 // GenCollectedHeap heap.
206 void VM_GenCollectFullConcurrent::doit() {
207 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
208 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
209
210 GenCollectedHeap* gch = GenCollectedHeap::heap();
211 if (_gc_count_before == gch->total_collections()) {
212 // The "full" of do_full_collection call below "forces"
213 // a collection; the second arg, 0, below ensures that
214 // only the young gen is collected. XXX In the future,
215 // we'll probably need to have something in this interface
216 // to say do this only if we are sure we will not bail
217 // out to a full collection in this attempt, but that's
218 // for the future.
219 assert(SafepointSynchronize::is_at_safepoint(),
220 "We can only be executing this arm of if at a safepoint");
221 GCCauseSetter gccs(gch, _gc_cause);
222 gch->do_full_collection(gch->must_clear_all_soft_refs(),
223 0 /* collect only youngest gen */);
224 } // Else no need for a foreground young gc
225 assert((_gc_count_before < gch->total_collections()) ||
226 (GC_locker::is_active() /* gc may have been skipped */
227 && (_gc_count_before == gch->total_collections())),
228 "total_collections() should be monotonically increasing");
229
230 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
231 assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
232 if (gch->total_full_collections() == _full_gc_count_before) {
233 // Disable iCMS until the full collection is done, and
234 // remember that we did so.
235 CMSCollector::disable_icms();
236 _disabled_icms = true;
237 // In case CMS thread was in icms_wait(), wake it up.
238 CMSCollector::start_icms();
239 // Nudge the CMS thread to start a concurrent collection.
240 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
241 } else {
242 assert(_full_gc_count_before < gch->total_full_collections(), "Error");
243 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
244 }
245 }
246
247 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
248 Thread* thr = Thread::current();
249 assert(thr != NULL, "Unexpected tid");
250 if (!thr->is_Java_thread()) {
251 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
252 GenCollectedHeap* gch = GenCollectedHeap::heap();
253 if (_gc_count_before != gch->total_collections()) {
254 // No need to do a young gc, we'll just nudge the CMS thread
255 // in the doit() method above, to be executed soon.
256 assert(_gc_count_before < gch->total_collections(),
257 "total_collections() should be monotnically increasing");
258 return false; // no need for foreground young gc
259 }
260 }
261 return true; // may still need foreground young gc
262 }
263
264
265 void VM_GenCollectFullConcurrent::doit_epilogue() {
266 Thread* thr = Thread::current();
267 assert(thr->is_Java_thread(), "just checking");
268 JavaThread* jt = (JavaThread*)thr;
269 // Release the Heap_lock first.
270 Heap_lock->unlock();
271 release_and_notify_pending_list_lock();
272
273 // It is fine to test whether completed collections has
274 // exceeded our request count without locking because
275 // the completion count is monotonically increasing;
276 // this will break for very long-running apps when the
277 // count overflows and wraps around. XXX fix me !!!
278 // e.g. at the rate of 1 full gc per ms, this could
279 // overflow in about 1000 years.
280 GenCollectedHeap* gch = GenCollectedHeap::heap();
281 if (_gc_cause != GCCause::_gc_locker &&
282 gch->total_full_collections_completed() <= _full_gc_count_before) {
283 // maybe we should change the condition to test _gc_cause ==
284 // GCCause::_java_lang_system_gc, instead of
285 // _gc_cause != GCCause::_gc_locker
286 assert(_gc_cause == GCCause::_java_lang_system_gc,
287 "the only way to get here if this was a System.gc()-induced GC");
288 assert(ExplicitGCInvokesConcurrent, "Error");
289 // Now, wait for witnessing concurrent gc cycle to complete,
290 // but do so in native mode, because we want to lock the
291 // FullGCEvent_lock, which may be needed by the VM thread
292 // or by the CMS thread, so we do not want to be suspended
293 // while holding that lock.
294 ThreadToNativeFromVM native(jt);
295 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
296 // Either a concurrent or a stop-world full gc is sufficient
297 // witness to our request.
298 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
299 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
300 }
301 }
302 // Enable iCMS back if we disabled it earlier.
303 if (_disabled_icms) {
304 CMSCollector::enable_icms();
305 }
306 }