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