1 /*
2 * Copyright (c) 2005, 2011, 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/gcTrace.hpp"
31 #include "gc_implementation/shared/gcTraceTime.hpp"
32 #include "gc_implementation/shared/isGCActiveMark.hpp"
33 #include "memory/gcLocker.inline.hpp"
34 #include "runtime/interfaceSupport.hpp"
35 #include "runtime/os.hpp"
36 #include "utilities/dtrace.hpp"
37
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 ConcurrentMarkSweepThread::slt()->
54 manipulatePLL(SurrogateLockerThread::acquirePLL);
55 }
56
57 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
58 // The caller may block while communicating
59 // with the SLT thread in order to acquire/release the PLL.
60 ConcurrentMarkSweepThread::slt()->
61 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
62 }
63
64 void VM_CMS_Operation::verify_before_gc() {
65 if (VerifyBeforeGC &&
66 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
67 GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm);
68 HandleMark hm;
69 FreelistLocker x(_collector);
70 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
71 Universe::heap()->prepare_for_verify();
72 Universe::verify();
73 }
74 }
75
76 void VM_CMS_Operation::verify_after_gc() {
77 if (VerifyAfterGC &&
78 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
79 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm);
80 HandleMark hm;
81 FreelistLocker x(_collector);
82 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
83 Universe::verify();
84 }
85 }
86
87 bool VM_CMS_Operation::lost_race() const {
88 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
89 // We lost a race to a foreground collection
90 // -- there's nothing to do
91 return true;
92 }
93 assert(CMSCollector::abstract_state() == legal_state(),
94 "Inconsistent collector state?");
95 return false;
96 }
97
98 bool VM_CMS_Operation::doit_prologue() {
99 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
100 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
101 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
102 "Possible deadlock");
103
104 if (needs_pll()) {
105 acquire_pending_list_lock();
106 }
107 // Get the Heap_lock after the pending_list_lock.
108 Heap_lock->lock();
109 if (lost_race()) {
110 assert(_prologue_succeeded == false, "Initialized in c'tor");
111 Heap_lock->unlock();
112 if (needs_pll()) {
113 release_and_notify_pending_list_lock();
114 }
115 } else {
116 _prologue_succeeded = true;
117 }
118 return _prologue_succeeded;
119 }
120
121 void VM_CMS_Operation::doit_epilogue() {
122 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
123 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
124 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
125 "Possible deadlock");
126
127 // Release the Heap_lock first.
128 Heap_lock->unlock();
129 if (needs_pll()) {
130 release_and_notify_pending_list_lock();
131 }
132 }
133
134 //////////////////////////////////////////////////////////
135 // Methods in class VM_CMS_Initial_Mark
136 //////////////////////////////////////////////////////////
137 void VM_CMS_Initial_Mark::doit() {
138 if (lost_race()) {
139 // Nothing to do.
140 return;
141 }
142 #ifndef USDT2
143 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
144 #else /* USDT2 */
145 HS_PRIVATE_CMS_INITMARK_BEGIN(
146 );
147 #endif /* USDT2 */
148
149 _collector->register_gc_start(GCCause::_cms_concurrent_mark);
150 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark", os::elapsed_counter());
151
152 GenCollectedHeap* gch = GenCollectedHeap::heap();
153 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
154
155 VM_CMS_Operation::verify_before_gc();
156
157 IsGCActiveMark x; // stop-world GC active
158 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
159
160 VM_CMS_Operation::verify_after_gc();
161
162 _collector->_gc_timer_cm->register_gc_pause_end(os::elapsed_counter());
163
164 #ifndef USDT2
165 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
166 #else /* USDT2 */
167 HS_PRIVATE_CMS_INITMARK_END(
168 );
169 #endif /* USDT2 */
170 }
171
172 //////////////////////////////////////////////////////////
173 // Methods in class VM_CMS_Final_Remark_Operation
174 //////////////////////////////////////////////////////////
175 void VM_CMS_Final_Remark::doit() {
176 if (lost_race()) {
177 // Nothing to do.
178 return;
179 }
180 #ifndef USDT2
181 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
182 #else /* USDT2 */
183 HS_PRIVATE_CMS_REMARK_BEGIN(
184 );
185 #endif /* USDT2 */
186
187 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark", os::elapsed_counter());
188
189 GenCollectedHeap* gch = GenCollectedHeap::heap();
190 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
191
192 VM_CMS_Operation::verify_before_gc();
193
194 IsGCActiveMark x; // stop-world GC active
195 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
196
197 VM_CMS_Operation::verify_after_gc();
198
199 _collector->_gc_timer_cm->register_gc_pause_end(os::elapsed_counter());
200
201 #ifndef USDT2
202 HS_DTRACE_PROBE(hs_private, cms__remark__end);
203 #else /* USDT2 */
204 HS_PRIVATE_CMS_REMARK_END(
205 );
206 #endif /* USDT2 */
207 }
208
209 // VM operation to invoke a concurrent collection of a
210 // GenCollectedHeap heap.
211 void VM_GenCollectFullConcurrent::doit() {
212 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
213 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
214
215 GenCollectedHeap* gch = GenCollectedHeap::heap();
216 if (_gc_count_before == gch->total_collections()) {
217 // The "full" of do_full_collection call below "forces"
218 // a collection; the second arg, 0, below ensures that
219 // only the young gen is collected. XXX In the future,
220 // we'll probably need to have something in this interface
221 // to say do this only if we are sure we will not bail
222 // out to a full collection in this attempt, but that's
223 // for the future.
224 assert(SafepointSynchronize::is_at_safepoint(),
225 "We can only be executing this arm of if at a safepoint");
226 GCCauseSetter gccs(gch, _gc_cause);
227 gch->do_full_collection(gch->must_clear_all_soft_refs(),
228 0 /* collect only youngest gen */);
229 } // Else no need for a foreground young gc
230 assert((_gc_count_before < gch->total_collections()) ||
231 (GC_locker::is_active() /* gc may have been skipped */
232 && (_gc_count_before == gch->total_collections())),
233 "total_collections() should be monotonically increasing");
234
235 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
236 assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
237 if (gch->total_full_collections() == _full_gc_count_before) {
238 // Disable iCMS until the full collection is done, and
239 // remember that we did so.
240 CMSCollector::disable_icms();
241 _disabled_icms = true;
242 // In case CMS thread was in icms_wait(), wake it up.
243 CMSCollector::start_icms();
244 // Nudge the CMS thread to start a concurrent collection.
245 CMSCollector::request_full_gc(_full_gc_count_before);
246 } else {
247 assert(_full_gc_count_before < gch->total_full_collections(), "Error");
248 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
249 }
250 }
251
252 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
253 Thread* thr = Thread::current();
254 assert(thr != NULL, "Unexpected tid");
255 if (!thr->is_Java_thread()) {
256 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
257 GenCollectedHeap* gch = GenCollectedHeap::heap();
258 if (_gc_count_before != gch->total_collections()) {
259 // No need to do a young gc, we'll just nudge the CMS thread
260 // in the doit() method above, to be executed soon.
261 assert(_gc_count_before < gch->total_collections(),
262 "total_collections() should be monotnically increasing");
263 return false; // no need for foreground young gc
264 }
265 }
266 return true; // may still need foreground young gc
267 }
268
269
270 void VM_GenCollectFullConcurrent::doit_epilogue() {
271 Thread* thr = Thread::current();
272 assert(thr->is_Java_thread(), "just checking");
273 JavaThread* jt = (JavaThread*)thr;
274 // Release the Heap_lock first.
275 Heap_lock->unlock();
276 release_and_notify_pending_list_lock();
277
278 // It is fine to test whether completed collections has
279 // exceeded our request count without locking because
280 // the completion count is monotonically increasing;
281 // this will break for very long-running apps when the
282 // count overflows and wraps around. XXX fix me !!!
283 // e.g. at the rate of 1 full gc per ms, this could
284 // overflow in about 1000 years.
285 GenCollectedHeap* gch = GenCollectedHeap::heap();
286 if (_gc_cause != GCCause::_gc_locker &&
287 gch->total_full_collections_completed() <= _full_gc_count_before) {
288 // maybe we should change the condition to test _gc_cause ==
289 // GCCause::_java_lang_system_gc, instead of
290 // _gc_cause != GCCause::_gc_locker
291 assert(_gc_cause == GCCause::_java_lang_system_gc,
292 "the only way to get here if this was a System.gc()-induced GC");
293 assert(ExplicitGCInvokesConcurrent, "Error");
294 // Now, wait for witnessing concurrent gc cycle to complete,
295 // but do so in native mode, because we want to lock the
296 // FullGCEvent_lock, which may be needed by the VM thread
297 // or by the CMS thread, so we do not want to be suspended
298 // while holding that lock.
299 ThreadToNativeFromVM native(jt);
300 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
301 // Either a concurrent or a stop-world full gc is sufficient
302 // witness to our request.
303 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
304 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
305 }
306 }
307 // Enable iCMS back if we disabled it earlier.
308 if (_disabled_icms) {
309 CMSCollector::enable_icms();
310 }
311 }