1 /*
2 * Copyright (c) 2005, 2014, 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 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
38
39 //////////////////////////////////////////////////////////
40 // Methods in abstract class VM_CMS_Operation
41 //////////////////////////////////////////////////////////
42 void VM_CMS_Operation::acquire_pending_list_lock() {
43 // The caller may block while communicating
44 // with the SLT thread in order to acquire/release the PLL.
45 if (SurrogateLockerThread* slt = ConcurrentMarkSweepThread::slt()) {
46 slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
47 } else {
48 SurrogateLockerThread::report_missing_slt();
49 }
50 }
51
52 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
53 // The caller may block while communicating
54 // with the SLT thread in order to acquire/release the PLL.
55 ConcurrentMarkSweepThread::slt()->
56 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
57 }
58
59 void VM_CMS_Operation::verify_before_gc() {
60 if (VerifyBeforeGC &&
61 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
62 GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id());
63 HandleMark hm;
64 FreelistLocker x(_collector);
65 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
66 Universe::heap()->prepare_for_verify();
67 Universe::verify();
68 }
69 }
70
71 void VM_CMS_Operation::verify_after_gc() {
72 if (VerifyAfterGC &&
73 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
74 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id());
75 HandleMark hm;
76 FreelistLocker x(_collector);
77 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
78 Universe::verify();
79 }
80 }
81
82 bool VM_CMS_Operation::lost_race() const {
83 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
84 // We lost a race to a foreground collection
85 // -- there's nothing to do
86 return true;
87 }
88 assert(CMSCollector::abstract_state() == legal_state(),
89 "Inconsistent collector state?");
90 return false;
91 }
92
93 bool VM_CMS_Operation::doit_prologue() {
94 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
95 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
96 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
97 "Possible deadlock");
98
99 if (needs_pll()) {
100 acquire_pending_list_lock();
101 }
102 // Get the Heap_lock after the pending_list_lock.
103 Heap_lock->lock();
104 if (lost_race()) {
105 assert(_prologue_succeeded == false, "Initialized in c'tor");
106 Heap_lock->unlock();
107 if (needs_pll()) {
108 release_and_notify_pending_list_lock();
109 }
110 } else {
111 _prologue_succeeded = true;
112 }
113 return _prologue_succeeded;
114 }
115
116 void VM_CMS_Operation::doit_epilogue() {
117 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
118 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
119 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
120 "Possible deadlock");
121
122 // Release the Heap_lock first.
123 Heap_lock->unlock();
124 if (needs_pll()) {
125 release_and_notify_pending_list_lock();
126 }
127 }
128
129 //////////////////////////////////////////////////////////
130 // Methods in class VM_CMS_Initial_Mark
131 //////////////////////////////////////////////////////////
132 void VM_CMS_Initial_Mark::doit() {
133 if (lost_race()) {
134 // Nothing to do.
135 return;
136 }
137 HS_PRIVATE_CMS_INITMARK_BEGIN();
138
139 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");
140
141 GenCollectedHeap* gch = GenCollectedHeap::heap();
142 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
143
144 VM_CMS_Operation::verify_before_gc();
145
146 IsGCActiveMark x; // stop-world GC active
147 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
148
149 VM_CMS_Operation::verify_after_gc();
150
151 _collector->_gc_timer_cm->register_gc_pause_end();
152
153 HS_PRIVATE_CMS_INITMARK_END();
154 }
155
156 //////////////////////////////////////////////////////////
157 // Methods in class VM_CMS_Final_Remark_Operation
158 //////////////////////////////////////////////////////////
159 void VM_CMS_Final_Remark::doit() {
160 if (lost_race()) {
161 // Nothing to do.
162 return;
163 }
164 HS_PRIVATE_CMS_REMARK_BEGIN();
165
166 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");
167
168 GenCollectedHeap* gch = GenCollectedHeap::heap();
169 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
170
171 VM_CMS_Operation::verify_before_gc();
172
173 IsGCActiveMark x; // stop-world GC active
174 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
175
176 VM_CMS_Operation::verify_after_gc();
177
178 _collector->save_heap_summary();
179 _collector->_gc_timer_cm->register_gc_pause_end();
180
181 HS_PRIVATE_CMS_REMARK_END();
182 }
183
184 // VM operation to invoke a concurrent collection of a
185 // GenCollectedHeap heap.
186 void VM_GenCollectFullConcurrent::doit() {
187 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
188 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
189
190 GenCollectedHeap* gch = GenCollectedHeap::heap();
191 if (_gc_count_before == gch->total_collections()) {
192 // The "full" of do_full_collection call below "forces"
193 // a collection; the second arg, 0, below ensures that
194 // only the young gen is collected. XXX In the future,
195 // we'll probably need to have something in this interface
196 // to say do this only if we are sure we will not bail
197 // out to a full collection in this attempt, but that's
198 // for the future.
199 assert(SafepointSynchronize::is_at_safepoint(),
200 "We can only be executing this arm of if at a safepoint");
201 GCCauseSetter gccs(gch, _gc_cause);
202 gch->do_full_collection(gch->must_clear_all_soft_refs(),
203 0 /* collect only youngest gen */);
204 } // Else no need for a foreground young gc
205 assert((_gc_count_before < gch->total_collections()) ||
206 (GC_locker::is_active() /* gc may have been skipped */
207 && (_gc_count_before == gch->total_collections())),
208 "total_collections() should be monotonically increasing");
209
210 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
211 assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
212 if (gch->total_full_collections() == _full_gc_count_before) {
213 // Nudge the CMS thread to start a concurrent collection.
214 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
215 } else {
216 assert(_full_gc_count_before < gch->total_full_collections(), "Error");
217 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
218 }
219 }
220
221 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
222 Thread* thr = Thread::current();
223 assert(thr != NULL, "Unexpected tid");
224 if (!thr->is_Java_thread()) {
225 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
226 GenCollectedHeap* gch = GenCollectedHeap::heap();
227 if (_gc_count_before != gch->total_collections()) {
228 // No need to do a young gc, we'll just nudge the CMS thread
229 // in the doit() method above, to be executed soon.
230 assert(_gc_count_before < gch->total_collections(),
231 "total_collections() should be monotonically increasing");
232 return false; // no need for foreground young gc
233 }
234 }
235 return true; // may still need foreground young gc
236 }
237
238
239 void VM_GenCollectFullConcurrent::doit_epilogue() {
240 Thread* thr = Thread::current();
241 assert(thr->is_Java_thread(), "just checking");
242 JavaThread* jt = (JavaThread*)thr;
243 // Release the Heap_lock first.
244 Heap_lock->unlock();
245 release_and_notify_pending_list_lock();
246
247 // It is fine to test whether completed collections has
248 // exceeded our request count without locking because
249 // the completion count is monotonically increasing;
250 // this will break for very long-running apps when the
251 // count overflows and wraps around. XXX fix me !!!
252 // e.g. at the rate of 1 full gc per ms, this could
253 // overflow in about 1000 years.
254 GenCollectedHeap* gch = GenCollectedHeap::heap();
255 if (_gc_cause != GCCause::_gc_locker &&
256 gch->total_full_collections_completed() <= _full_gc_count_before) {
257 // maybe we should change the condition to test _gc_cause ==
258 // GCCause::_java_lang_system_gc, instead of
259 // _gc_cause != GCCause::_gc_locker
260 assert(_gc_cause == GCCause::_java_lang_system_gc,
261 "the only way to get here if this was a System.gc()-induced GC");
262 assert(ExplicitGCInvokesConcurrent, "Error");
263 // Now, wait for witnessing concurrent gc cycle to complete,
264 // but do so in native mode, because we want to lock the
265 // FullGCEvent_lock, which may be needed by the VM thread
266 // or by the CMS thread, so we do not want to be suspended
267 // while holding that lock.
268 ThreadToNativeFromVM native(jt);
269 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
270 // Either a concurrent or a stop-world full gc is sufficient
271 // witness to our request.
272 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
273 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
274 }
275 }
276 }