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