1 /*
2 * Copyright (c) 2005, 2016, 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::verify_before_gc() {
41 if (VerifyBeforeGC &&
42 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
43 GCTraceTime(Info, gc, phases, verify) tm("Verify Before", _collector->_gc_timer_cm);
44 HandleMark hm;
45 FreelistLocker x(_collector);
46 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
47 GenCollectedHeap::heap()->prepare_for_verify();
48 Universe::verify();
49 }
50 }
51
52 void VM_CMS_Operation::verify_after_gc() {
53 if (VerifyAfterGC &&
54 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
55 GCTraceTime(Info, gc, phases, verify) tm("Verify After", _collector->_gc_timer_cm);
56 HandleMark hm;
57 FreelistLocker x(_collector);
58 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
59 Universe::verify();
60 }
61 }
62
63 bool VM_CMS_Operation::lost_race() const {
64 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
65 // We lost a race to a foreground collection
66 // -- there's nothing to do
67 return true;
68 }
69 assert(CMSCollector::abstract_state() == legal_state(),
70 "Inconsistent collector state?");
71 return false;
72 }
73
74 bool VM_CMS_Operation::doit_prologue() {
75 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
76 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
77 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
78 "Possible deadlock");
79
80 Heap_lock->lock();
81 if (lost_race()) {
82 assert(_prologue_succeeded == false, "Initialized in c'tor");
83 Heap_lock->unlock();
84 } else {
85 _prologue_succeeded = true;
86 }
87 return _prologue_succeeded;
88 }
89
90 void VM_CMS_Operation::doit_epilogue() {
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 (Universe::has_reference_pending_list()) {
97 Heap_lock->notify_all();
98 }
99 Heap_lock->unlock();
100 }
101
102 //////////////////////////////////////////////////////////
103 // Methods in class VM_CMS_Initial_Mark
104 //////////////////////////////////////////////////////////
105 void VM_CMS_Initial_Mark::doit() {
106 if (lost_race()) {
107 // Nothing to do.
108 return;
109 }
110 HS_PRIVATE_CMS_INITMARK_BEGIN();
111 GCIdMark gc_id_mark(_gc_id);
112
113 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");
114
115 GenCollectedHeap* gch = GenCollectedHeap::heap();
116 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
117
118 VM_CMS_Operation::verify_before_gc();
119
120 IsGCActiveMark x; // stop-world GC active
121 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, gch->gc_cause());
122
123 VM_CMS_Operation::verify_after_gc();
124
125 _collector->_gc_timer_cm->register_gc_pause_end();
126
127 HS_PRIVATE_CMS_INITMARK_END();
128 }
129
130 //////////////////////////////////////////////////////////
131 // Methods in class VM_CMS_Final_Remark_Operation
132 //////////////////////////////////////////////////////////
133 void VM_CMS_Final_Remark::doit() {
134 if (lost_race()) {
135 // Nothing to do.
136 return;
137 }
138 HS_PRIVATE_CMS_REMARK_BEGIN();
139 GCIdMark gc_id_mark(_gc_id);
140
141 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");
142
143 GenCollectedHeap* gch = GenCollectedHeap::heap();
144 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
145
146 VM_CMS_Operation::verify_before_gc();
147
148 IsGCActiveMark x; // stop-world GC active
149 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, gch->gc_cause());
150
151 VM_CMS_Operation::verify_after_gc();
152
153 _collector->save_heap_summary();
154 _collector->_gc_timer_cm->register_gc_pause_end();
155
156 HS_PRIVATE_CMS_REMARK_END();
157 }
158
159 // VM operation to invoke a concurrent collection of a
160 // GenCollectedHeap heap.
161 void VM_GenCollectFullConcurrent::doit() {
162 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
163 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
164
165 GenCollectedHeap* gch = GenCollectedHeap::heap();
166 if (_gc_count_before == gch->total_collections()) {
167 // The "full" of do_full_collection call below "forces"
168 // a collection; the second arg, 0, below ensures that
169 // only the young gen is collected. XXX In the future,
170 // we'll probably need to have something in this interface
171 // to say do this only if we are sure we will not bail
172 // out to a full collection in this attempt, but that's
173 // for the future.
174 assert(SafepointSynchronize::is_at_safepoint(),
175 "We can only be executing this arm of if at a safepoint");
176 GCCauseSetter gccs(gch, _gc_cause);
177 gch->do_full_collection(gch->must_clear_all_soft_refs(), GenCollectedHeap::YoungGen);
178 } // Else no need for a foreground young gc
179 assert((_gc_count_before < gch->total_collections()) ||
180 (GCLocker::is_active() /* gc may have been skipped */
181 && (_gc_count_before == gch->total_collections())),
182 "total_collections() should be monotonically increasing");
183
184 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
185 assert(_full_gc_count_before <= gch->total_full_collections(), "Error");
186 if (gch->total_full_collections() == _full_gc_count_before) {
187 // Nudge the CMS thread to start a concurrent collection.
188 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
189 } else {
190 assert(_full_gc_count_before < gch->total_full_collections(), "Error");
191 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
192 }
193 }
194
195 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
196 Thread* thr = Thread::current();
197 assert(thr != NULL, "Unexpected tid");
198 if (!thr->is_Java_thread()) {
199 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
200 GenCollectedHeap* gch = GenCollectedHeap::heap();
201 if (_gc_count_before != gch->total_collections()) {
202 // No need to do a young gc, we'll just nudge the CMS thread
203 // in the doit() method above, to be executed soon.
204 assert(_gc_count_before < gch->total_collections(),
205 "total_collections() should be monotonically increasing");
206 return false; // no need for foreground young gc
207 }
208 }
209 return true; // may still need foreground young gc
210 }
211
212
213 void VM_GenCollectFullConcurrent::doit_epilogue() {
214 Thread* thr = Thread::current();
215 assert(thr->is_Java_thread(), "just checking");
216 JavaThread* jt = (JavaThread*)thr;
217
218 if (Universe::has_reference_pending_list()) {
219 Heap_lock->notify_all();
220 }
221 Heap_lock->unlock();
222
223 // It is fine to test whether completed collections has
224 // exceeded our request count without locking because
225 // the completion count is monotonically increasing;
226 // this will break for very long-running apps when the
227 // count overflows and wraps around. XXX fix me !!!
228 // e.g. at the rate of 1 full gc per ms, this could
229 // overflow in about 1000 years.
230 GenCollectedHeap* gch = GenCollectedHeap::heap();
231 if (_gc_cause != GCCause::_gc_locker &&
232 gch->total_full_collections_completed() <= _full_gc_count_before) {
233 // maybe we should change the condition to test _gc_cause ==
234 // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run,
235 // instead of _gc_cause != GCCause::_gc_locker
236 assert(GCCause::is_user_requested_gc(_gc_cause),
237 "the only way to get here if this was a System.gc()-induced GC");
238 assert(ExplicitGCInvokesConcurrent, "Error");
239 // Now, wait for witnessing concurrent gc cycle to complete,
240 // but do so in native mode, because we want to lock the
241 // FullGCEvent_lock, which may be needed by the VM thread
242 // or by the CMS thread, so we do not want to be suspended
243 // while holding that lock.
244 ThreadToNativeFromVM native(jt);
245 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
246 // Either a concurrent or a stop-world full gc is sufficient
247 // witness to our request.
248 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
249 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
250 }
251 }
252 }