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/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
38 #ifndef USDT2
39 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
40 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
41
42 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
43 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
44 #endif /* !USDT2 */
45
46 //////////////////////////////////////////////////////////
47 // Methods in abstract class VM_CMS_Operation
48 //////////////////////////////////////////////////////////
49 void VM_CMS_Operation::acquire_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::acquirePLL);
54 }
55
56 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
57 // The caller may block while communicating
58 // with the SLT thread in order to acquire/release the PLL.
59 ConcurrentMarkSweepThread::slt()->
60 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
61 }
62
63 void VM_CMS_Operation::verify_before_gc() {
64 if (VerifyBeforeGC &&
65 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
66 GCTraceTime tm("Verify Before", false, false, _collector->_gc_timer_cm);
67 HandleMark hm;
68 FreelistLocker x(_collector);
69 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
70 Universe::heap()->prepare_for_verify();
71 Universe::verify();
72 }
73 }
74
75 void VM_CMS_Operation::verify_after_gc() {
76 if (VerifyAfterGC &&
77 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
78 GCTraceTime tm("Verify After", false, false, _collector->_gc_timer_cm);
79 HandleMark hm;
80 FreelistLocker x(_collector);
81 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
82 Universe::verify();
83 }
84 }
85
86 bool VM_CMS_Operation::lost_race() const {
87 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
88 // We lost a race to a foreground collection
89 // -- there's nothing to do
90 return true;
91 }
92 assert(CMSCollector::abstract_state() == legal_state(),
93 "Inconsistent collector state?");
94 return false;
95 }
96
97 bool VM_CMS_Operation::doit_prologue() {
98 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
99 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
100 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
101 "Possible deadlock");
102
103 if (needs_pll()) {
104 acquire_pending_list_lock();
105 }
106 // Get the Heap_lock after the pending_list_lock.
107 Heap_lock->lock();
108 if (lost_race()) {
109 assert(_prologue_succeeded == false, "Initialized in c'tor");
110 Heap_lock->unlock();
111 if (needs_pll()) {
112 release_and_notify_pending_list_lock();
113 }
114 } else {
115 _prologue_succeeded = true;
116 }
117 return _prologue_succeeded;
118 }
119
120 void VM_CMS_Operation::doit_epilogue() {
121 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
122 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
123 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
124 "Possible deadlock");
125
126 // Release the Heap_lock first.
127 Heap_lock->unlock();
128 if (needs_pll()) {
129 release_and_notify_pending_list_lock();
130 }
131 }
132
133 //////////////////////////////////////////////////////////
134 // Methods in class VM_CMS_Initial_Mark
135 //////////////////////////////////////////////////////////
136 void VM_CMS_Initial_Mark::doit() {
137 if (lost_race()) {
138 // Nothing to do.
139 return;
140 }
141 #ifndef USDT2
142 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
143 #else /* USDT2 */
144 HS_PRIVATE_CMS_INITMARK_BEGIN(
145 );
146 #endif /* USDT2 */
147
148 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark", os::elapsed_counter());
149
150 GenCollectedHeap* gch = GenCollectedHeap::heap();
151 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
152
153 VM_CMS_Operation::verify_before_gc();
154
155 IsGCActiveMark x; // stop-world GC active
156 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
157
158 VM_CMS_Operation::verify_after_gc();
159
160 _collector->_gc_timer_cm->register_gc_pause_end(os::elapsed_counter());
161
162 #ifndef USDT2
163 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
164 #else /* USDT2 */
165 HS_PRIVATE_CMS_INITMARK_END(
166 );
167 #endif /* USDT2 */
168 }
169
170 //////////////////////////////////////////////////////////
171 // Methods in class VM_CMS_Final_Remark_Operation
172 //////////////////////////////////////////////////////////
173 void VM_CMS_Final_Remark::doit() {
174 if (lost_race()) {
175 // Nothing to do.
176 return;
177 }
178 #ifndef USDT2
179 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
180 #else /* USDT2 */
181 HS_PRIVATE_CMS_REMARK_BEGIN(
182 );
183 #endif /* USDT2 */
184
185 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark", os::elapsed_counter());
186
187 GenCollectedHeap* gch = GenCollectedHeap::heap();
188 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
189
190 VM_CMS_Operation::verify_before_gc();
191
192 IsGCActiveMark x; // stop-world GC active
193 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
194
195 VM_CMS_Operation::verify_after_gc();
196
197 _collector->_gc_timer_cm->register_gc_pause_end(os::elapsed_counter());
198
199 #ifndef USDT2
200 HS_DTRACE_PROBE(hs_private, cms__remark__end);
201 #else /* USDT2 */
202 HS_PRIVATE_CMS_REMARK_END(
203 );
204 #endif /* USDT2 */
205 }
206
207 // VM operation to invoke a concurrent collection of a
208 // GenCollectedHeap heap.
209 void VM_GenCollectFullConcurrent::doit() {
210 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
211 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
212
213 GenCollectedHeap* gch = GenCollectedHeap::heap();
214 if (_gc_count_before == gch->total_collections()) {
215 // The "full" of do_full_collection call below "forces"
216 // a collection; the second arg, 0, below ensures that
217 // only the young gen is collected. XXX In the future,
218 // we'll probably need to have something in this interface
219 // to say do this only if we are sure we will not bail
220 // out to a full collection in this attempt, but that's
221 // for the future.
222 assert(SafepointSynchronize::is_at_safepoint(),
223 "We can only be executing this arm of if at a safepoint");
224 GCCauseSetter gccs(gch, _gc_cause);
225 gch->do_full_collection(gch->must_clear_all_soft_refs(),
226 0 /* collect only youngest gen */);
227 } // Else no need for a foreground young gc
228 assert((_gc_count_before < gch->total_collections()) ||
229 (GC_locker::is_active() /* gc may have been skipped */
230 && (_gc_count_before == gch->total_collections())),
231 "total_collections() should be monotonically increasing");
232
233 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
234 assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
235 if (gch->total_full_collections() == _full_gc_count_before) {
236 // Disable iCMS until the full collection is done, and
237 // remember that we did so.
238 CMSCollector::disable_icms();
239 _disabled_icms = true;
240 // In case CMS thread was in icms_wait(), wake it up.
241 CMSCollector::start_icms();
242 // Nudge the CMS thread to start a concurrent collection.
243 CMSCollector::request_full_gc(_full_gc_count_before);
244 } else {
245 assert(_full_gc_count_before < gch->total_full_collections(), "Error");
246 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
247 }
248 }
249
250 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
251 Thread* thr = Thread::current();
252 assert(thr != NULL, "Unexpected tid");
253 if (!thr->is_Java_thread()) {
254 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
255 GenCollectedHeap* gch = GenCollectedHeap::heap();
256 if (_gc_count_before != gch->total_collections()) {
257 // No need to do a young gc, we'll just nudge the CMS thread
258 // in the doit() method above, to be executed soon.
259 assert(_gc_count_before < gch->total_collections(),
260 "total_collections() should be monotnically increasing");
261 return false; // no need for foreground young gc
262 }
263 }
264 return true; // may still need foreground young gc
265 }
266
267
268 void VM_GenCollectFullConcurrent::doit_epilogue() {
269 Thread* thr = Thread::current();
270 assert(thr->is_Java_thread(), "just checking");
271 JavaThread* jt = (JavaThread*)thr;
272 // Release the Heap_lock first.
273 Heap_lock->unlock();
274 release_and_notify_pending_list_lock();
275
276 // It is fine to test whether completed collections has
277 // exceeded our request count without locking because
278 // the completion count is monotonically increasing;
279 // this will break for very long-running apps when the
280 // count overflows and wraps around. XXX fix me !!!
281 // e.g. at the rate of 1 full gc per ms, this could
282 // overflow in about 1000 years.
283 GenCollectedHeap* gch = GenCollectedHeap::heap();
284 if (_gc_cause != GCCause::_gc_locker &&
285 gch->total_full_collections_completed() <= _full_gc_count_before) {
286 // maybe we should change the condition to test _gc_cause ==
287 // GCCause::_java_lang_system_gc, instead of
288 // _gc_cause != GCCause::_gc_locker
289 assert(_gc_cause == GCCause::_java_lang_system_gc,
290 "the only way to get here if this was a System.gc()-induced GC");
291 assert(ExplicitGCInvokesConcurrent, "Error");
292 // Now, wait for witnessing concurrent gc cycle to complete,
293 // but do so in native mode, because we want to lock the
294 // FullGCEvent_lock, which may be needed by the VM thread
295 // or by the CMS thread, so we do not want to be suspended
296 // while holding that lock.
297 ThreadToNativeFromVM native(jt);
298 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
299 // Either a concurrent or a stop-world full gc is sufficient
300 // witness to our request.
301 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
302 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
303 }
304 }
305 // Enable iCMS back if we disabled it earlier.
306 if (_disabled_icms) {
307 CMSCollector::enable_icms();
308 }
309 }