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 #ifndef USDT2
40 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
41 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
42
43 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
44 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
45 #endif /* !USDT2 */
46
47 //////////////////////////////////////////////////////////
48 // Methods in abstract class VM_CMS_Operation
49 //////////////////////////////////////////////////////////
50 void VM_CMS_Operation::acquire_pending_list_lock() {
51 // The caller may block while communicating
52 // with the SLT thread in order to acquire/release the PLL.
53 SurrogateLockerThread* slt = ConcurrentMarkSweepThread::slt();
54 if (slt != NULL) {
55 slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
56 } else {
57 SurrogateLockerThread::report_missing_slt();
58 }
59 }
60
61 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
62 // The caller may block while communicating
63 // with the SLT thread in order to acquire/release the PLL.
64 ConcurrentMarkSweepThread::slt()->
65 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
66 }
67
68 void VM_CMS_Operation::verify_before_gc() {
69 if (VerifyBeforeGC &&
70 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
71 GCTraceTime tm("Verify Before", 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::heap()->prepare_for_verify();
76 Universe::verify();
77 }
78 }
79
80 void VM_CMS_Operation::verify_after_gc() {
81 if (VerifyAfterGC &&
82 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
83 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm, _collector->_gc_tracer_cm->gc_id());
84 HandleMark hm;
85 FreelistLocker x(_collector);
86 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
87 Universe::verify();
88 }
89 }
90
91 bool VM_CMS_Operation::lost_race() const {
92 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
93 // We lost a race to a foreground collection
94 // -- there's nothing to do
95 return true;
96 }
97 assert(CMSCollector::abstract_state() == legal_state(),
98 "Inconsistent collector state?");
99 return false;
100 }
101
102 bool VM_CMS_Operation::doit_prologue() {
103 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
104 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
105 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
106 "Possible deadlock");
107
108 if (needs_pll()) {
109 acquire_pending_list_lock();
110 }
111 // Get the Heap_lock after the pending_list_lock.
112 Heap_lock->lock();
113 if (lost_race()) {
114 assert(_prologue_succeeded == false, "Initialized in c'tor");
115 Heap_lock->unlock();
116 if (needs_pll()) {
117 release_and_notify_pending_list_lock();
118 }
119 } else {
120 _prologue_succeeded = true;
121 }
122 return _prologue_succeeded;
123 }
124
125 void VM_CMS_Operation::doit_epilogue() {
126 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
127 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
128 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
129 "Possible deadlock");
130
131 // Release the Heap_lock first.
132 Heap_lock->unlock();
133 if (needs_pll()) {
134 release_and_notify_pending_list_lock();
135 }
136 }
137
138 //////////////////////////////////////////////////////////
139 // Methods in class VM_CMS_Initial_Mark
140 //////////////////////////////////////////////////////////
141 void VM_CMS_Initial_Mark::doit() {
142 if (lost_race()) {
143 // Nothing to do.
144 return;
145 }
146 #ifndef USDT2
147 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
148 #else /* USDT2 */
149 HS_PRIVATE_CMS_INITMARK_BEGIN(
150 );
151 #endif /* USDT2 */
152
153 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");
154
155 GenCollectedHeap* gch = GenCollectedHeap::heap();
156 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
157
158 VM_CMS_Operation::verify_before_gc();
159
160 IsGCActiveMark x; // stop-world GC active
161 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
162
163 VM_CMS_Operation::verify_after_gc();
164
165 _collector->_gc_timer_cm->register_gc_pause_end();
166
167 #ifndef USDT2
168 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
169 #else /* USDT2 */
170 HS_PRIVATE_CMS_INITMARK_END(
171 );
172 #endif /* USDT2 */
173 }
174
175 //////////////////////////////////////////////////////////
176 // Methods in class VM_CMS_Final_Remark_Operation
177 //////////////////////////////////////////////////////////
178 void VM_CMS_Final_Remark::doit() {
179 if (lost_race()) {
180 // Nothing to do.
181 return;
182 }
183 #ifndef USDT2
184 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
185 #else /* USDT2 */
186 HS_PRIVATE_CMS_REMARK_BEGIN(
187 );
188 #endif /* USDT2 */
189
190 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");
191
192 GenCollectedHeap* gch = GenCollectedHeap::heap();
193 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
194
195 VM_CMS_Operation::verify_before_gc();
196
197 IsGCActiveMark x; // stop-world GC active
198 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
199
200 VM_CMS_Operation::verify_after_gc();
201
202 _collector->save_heap_summary();
203 _collector->_gc_timer_cm->register_gc_pause_end();
204
205 #ifndef USDT2
206 HS_DTRACE_PROBE(hs_private, cms__remark__end);
207 #else /* USDT2 */
208 HS_PRIVATE_CMS_REMARK_END(
209 );
210 #endif /* USDT2 */
211 }
212
213 // VM operation to invoke a concurrent collection of a
214 // GenCollectedHeap heap.
215 void VM_GenCollectFullConcurrent::doit() {
216 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
217 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
218
219 GenCollectedHeap* gch = GenCollectedHeap::heap();
220 if (_gc_count_before == gch->total_collections()) {
221 // The "full" of do_full_collection call below "forces"
222 // a collection; the second arg, 0, below ensures that
223 // only the young gen is collected. XXX In the future,
224 // we'll probably need to have something in this interface
225 // to say do this only if we are sure we will not bail
226 // out to a full collection in this attempt, but that's
227 // for the future.
228 assert(SafepointSynchronize::is_at_safepoint(),
229 "We can only be executing this arm of if at a safepoint");
230 GCCauseSetter gccs(gch, _gc_cause);
231 gch->do_full_collection(gch->must_clear_all_soft_refs(),
232 0 /* collect only youngest gen */);
233 } // Else no need for a foreground young gc
234 assert((_gc_count_before < gch->total_collections()) ||
235 (GC_locker::is_active() /* gc may have been skipped */
236 && (_gc_count_before == gch->total_collections())),
237 "total_collections() should be monotonically increasing");
238
239 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
240 assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
241 if (gch->total_full_collections() == _full_gc_count_before) {
242 // Disable iCMS until the full collection is done, and
243 // remember that we did so.
244 CMSCollector::disable_icms();
245 _disabled_icms = true;
246 // In case CMS thread was in icms_wait(), wake it up.
247 CMSCollector::start_icms();
248 // Nudge the CMS thread to start a concurrent collection.
249 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
250 } else {
251 assert(_full_gc_count_before < gch->total_full_collections(), "Error");
252 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
253 }
254 }
255
256 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
257 Thread* thr = Thread::current();
258 assert(thr != NULL, "Unexpected tid");
259 if (!thr->is_Java_thread()) {
260 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
261 GenCollectedHeap* gch = GenCollectedHeap::heap();
262 if (_gc_count_before != gch->total_collections()) {
263 // No need to do a young gc, we'll just nudge the CMS thread
264 // in the doit() method above, to be executed soon.
265 assert(_gc_count_before < gch->total_collections(),
266 "total_collections() should be monotnically increasing");
267 return false; // no need for foreground young gc
268 }
269 }
270 return true; // may still need foreground young gc
271 }
272
273
274 void VM_GenCollectFullConcurrent::doit_epilogue() {
275 Thread* thr = Thread::current();
276 assert(thr->is_Java_thread(), "just checking");
277 JavaThread* jt = (JavaThread*)thr;
278 // Release the Heap_lock first.
279 Heap_lock->unlock();
280 release_and_notify_pending_list_lock();
281
282 // It is fine to test whether completed collections has
283 // exceeded our request count without locking because
284 // the completion count is monotonically increasing;
285 // this will break for very long-running apps when the
286 // count overflows and wraps around. XXX fix me !!!
287 // e.g. at the rate of 1 full gc per ms, this could
288 // overflow in about 1000 years.
289 GenCollectedHeap* gch = GenCollectedHeap::heap();
290 if (_gc_cause != GCCause::_gc_locker &&
291 gch->total_full_collections_completed() <= _full_gc_count_before) {
292 // maybe we should change the condition to test _gc_cause ==
293 // GCCause::_java_lang_system_gc, instead of
294 // _gc_cause != GCCause::_gc_locker
295 assert(_gc_cause == GCCause::_java_lang_system_gc,
296 "the only way to get here if this was a System.gc()-induced GC");
297 assert(ExplicitGCInvokesConcurrent, "Error");
298 // Now, wait for witnessing concurrent gc cycle to complete,
299 // but do so in native mode, because we want to lock the
300 // FullGCEvent_lock, which may be needed by the VM thread
301 // or by the CMS thread, so we do not want to be suspended
302 // while holding that lock.
303 ThreadToNativeFromVM native(jt);
304 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
305 // Either a concurrent or a stop-world full gc is sufficient
306 // witness to our request.
307 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
308 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
309 }
310 }
311 // Enable iCMS back if we disabled it earlier.
312 if (_disabled_icms) {
313 CMSCollector::enable_icms();
314 }
315 }