1 /*
2 * Copyright (c) 2005, 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 "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
27 #include "gc/cms/concurrentMarkSweepThread.hpp"
28 #include "gc/cms/vmCMSOperations.hpp"
29 #include "gc/shared/gcLocker.inline.hpp"
30 #include "gc/shared/gcTimer.hpp"
31 #include "gc/shared/gcTraceTime.inline.hpp"
32 #include "gc/shared/isGCActiveMark.hpp"
33 #include "runtime/interfaceSupport.hpp"
34 #include "runtime/os.hpp"
35 #include "utilities/dtrace.hpp"
36
37 //////////////////////////////////////////////////////////
38 // Methods in abstract class VM_CMS_Operation
39 //////////////////////////////////////////////////////////
40 void VM_CMS_Operation::acquire_pending_list_lock() {
41 // The caller may block while communicating
42 // with the SLT thread in order to acquire/release the PLL.
43 SurrogateLockerThread* slt = ConcurrentMarkSweepThread::slt();
44 if (slt != NULL) {
45 slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
46 } else {
47 SurrogateLockerThread::report_missing_slt();
48 }
49 }
50
51 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
52 // The caller may block while communicating
53 // with the SLT thread in order to acquire/release the PLL.
54 ConcurrentMarkSweepThread::slt()->
55 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
56 }
57
58 void VM_CMS_Operation::verify_before_gc() {
59 if (VerifyBeforeGC &&
60 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
61 GCTraceTime(Info, gc, verify) tm("Verify Before", _collector->_gc_timer_cm);
62 HandleMark hm;
63 FreelistLocker x(_collector);
64 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
65 GenCollectedHeap::heap()->prepare_for_verify();
66 Universe::verify();
67 }
68 }
69
70 void VM_CMS_Operation::verify_after_gc() {
71 if (VerifyAfterGC &&
72 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
73 GCTraceTime(Info, gc, verify) tm("Verify After", _collector->_gc_timer_cm);
74 HandleMark hm;
75 FreelistLocker x(_collector);
76 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
77 Universe::verify();
78 }
79 }
80
81 bool VM_CMS_Operation::lost_race() const {
82 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
83 // We lost a race to a foreground collection
84 // -- there's nothing to do
85 return true;
86 }
87 assert(CMSCollector::abstract_state() == legal_state(),
88 "Inconsistent collector state?");
89 return false;
90 }
91
92 bool VM_CMS_Operation::doit_prologue() {
93 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
94 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
95 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
96 "Possible deadlock");
97
98 if (needs_pll()) {
99 acquire_pending_list_lock();
100 }
101 // Get the Heap_lock after the pending_list_lock.
102 Heap_lock->lock();
103 if (lost_race()) {
104 assert(_prologue_succeeded == false, "Initialized in c'tor");
105 Heap_lock->unlock();
106 if (needs_pll()) {
107 release_and_notify_pending_list_lock();
108 }
109 } else {
110 _prologue_succeeded = true;
111 }
112 return _prologue_succeeded;
113 }
114
115 void VM_CMS_Operation::doit_epilogue() {
116 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
117 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
118 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
119 "Possible deadlock");
120
121 // Release the Heap_lock first.
122 Heap_lock->unlock();
123 if (needs_pll()) {
124 release_and_notify_pending_list_lock();
125 }
126 }
127
128 //////////////////////////////////////////////////////////
129 // Methods in class VM_CMS_Initial_Mark
130 //////////////////////////////////////////////////////////
131 void VM_CMS_Initial_Mark::doit() {
132 if (lost_race()) {
133 // Nothing to do.
134 return;
135 }
136 HS_PRIVATE_CMS_INITMARK_BEGIN();
137 GCIdMark gc_id_mark(_gc_id);
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 GCIdMark gc_id_mark(_gc_id);
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(), GenCollectedHeap::YoungGen);
204 } // Else no need for a foreground young gc
205 assert((_gc_count_before < gch->total_collections()) ||
206 (GCLocker::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 or GCCause::_dcmd_gc_run,
259 // instead of _gc_cause != GCCause::_gc_locker
260 assert(GCCause::is_user_requested_gc(_gc_cause),
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 }