1 /*
2 * Copyright (c) 2005, 2017, 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/cmsHeap.hpp"
27 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
28 #include "gc/cms/concurrentMarkSweepThread.hpp"
29 #include "gc/cms/vmCMSOperations.hpp"
30 #include "gc/shared/gcLocker.inline.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/gcTraceTime.inline.hpp"
33 #include "gc/shared/isGCActiveMark.hpp"
34 #include "runtime/interfaceSupport.hpp"
35 #include "runtime/os.hpp"
36 #include "utilities/dtrace.hpp"
37
38 //////////////////////////////////////////////////////////
39 // Methods in abstract class VM_CMS_Operation
40 //////////////////////////////////////////////////////////
41 void VM_CMS_Operation::verify_before_gc() {
42 if (VerifyBeforeGC &&
43 CMSHeap::heap()->total_collections() >= VerifyGCStartAt) {
44 GCTraceTime(Info, gc, phases, verify) tm("Verify Before", _collector->_gc_timer_cm);
45 HandleMark hm;
46 FreelistLocker x(_collector);
47 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
48 CMSHeap::heap()->prepare_for_verify();
49 Universe::verify();
50 }
51 }
52
53 void VM_CMS_Operation::verify_after_gc() {
54 if (VerifyAfterGC &&
55 CMSHeap::heap()->total_collections() >= VerifyGCStartAt) {
56 GCTraceTime(Info, gc, phases, verify) tm("Verify After", _collector->_gc_timer_cm);
57 HandleMark hm;
58 FreelistLocker x(_collector);
59 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
60 Universe::verify();
61 }
62 }
63
64 bool VM_CMS_Operation::lost_race() const {
65 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
66 // We lost a race to a foreground collection
67 // -- there's nothing to do
68 return true;
69 }
70 assert(CMSCollector::abstract_state() == legal_state(),
71 "Inconsistent collector state?");
72 return false;
73 }
74
75 bool VM_CMS_Operation::doit_prologue() {
76 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
77 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
78 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
79 "Possible deadlock");
80
81 Heap_lock->lock();
82 if (lost_race()) {
83 assert(_prologue_succeeded == false, "Initialized in c'tor");
84 Heap_lock->unlock();
85 } else {
86 _prologue_succeeded = true;
87 }
88 return _prologue_succeeded;
89 }
90
91 void VM_CMS_Operation::doit_epilogue() {
92 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
93 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
94 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
95 "Possible deadlock");
96
97 if (Universe::has_reference_pending_list()) {
98 Heap_lock->notify_all();
99 }
100 Heap_lock->unlock();
101 }
102
103 //////////////////////////////////////////////////////////
104 // Methods in class VM_CMS_Initial_Mark
105 //////////////////////////////////////////////////////////
106 void VM_CMS_Initial_Mark::doit() {
107 if (lost_race()) {
108 // Nothing to do.
109 return;
110 }
111 HS_PRIVATE_CMS_INITMARK_BEGIN();
112 GCIdMark gc_id_mark(_gc_id);
113
114 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");
115
116 CMSHeap* heap = CMSHeap::heap();
117 GCCauseSetter gccs(heap, GCCause::_cms_initial_mark);
118
119 VM_CMS_Operation::verify_before_gc();
120
121 IsGCActiveMark x; // stop-world GC active
122 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, heap->gc_cause());
123
124 VM_CMS_Operation::verify_after_gc();
125
126 _collector->_gc_timer_cm->register_gc_pause_end();
127
128 HS_PRIVATE_CMS_INITMARK_END();
129 }
130
131 //////////////////////////////////////////////////////////
132 // Methods in class VM_CMS_Final_Remark_Operation
133 //////////////////////////////////////////////////////////
134 void VM_CMS_Final_Remark::doit() {
135 if (lost_race()) {
136 // Nothing to do.
137 return;
138 }
139 HS_PRIVATE_CMS_REMARK_BEGIN();
140 GCIdMark gc_id_mark(_gc_id);
141
142 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");
143
144 CMSHeap* heap = CMSHeap::heap();
145 GCCauseSetter gccs(heap, GCCause::_cms_final_remark);
146
147 VM_CMS_Operation::verify_before_gc();
148
149 IsGCActiveMark x; // stop-world GC active
150 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, heap->gc_cause());
151
152 VM_CMS_Operation::verify_after_gc();
153
154 _collector->save_heap_summary();
155 _collector->_gc_timer_cm->register_gc_pause_end();
156
157 HS_PRIVATE_CMS_REMARK_END();
158 }
159
160 // VM operation to invoke a concurrent collection of a
161 // GenCollectedHeap heap.
162 void VM_GenCollectFullConcurrent::doit() {
163 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
164 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
165
166 CMSHeap* heap = CMSHeap::heap();
167 if (_gc_count_before == heap->total_collections()) {
168 // The "full" of do_full_collection call below "forces"
169 // a collection; the second arg, 0, below ensures that
170 // only the young gen is collected. XXX In the future,
171 // we'll probably need to have something in this interface
172 // to say do this only if we are sure we will not bail
173 // out to a full collection in this attempt, but that's
174 // for the future.
175 assert(SafepointSynchronize::is_at_safepoint(),
176 "We can only be executing this arm of if at a safepoint");
177 GCCauseSetter gccs(heap, _gc_cause);
178 heap->do_full_collection(heap->must_clear_all_soft_refs(), GenCollectedHeap::YoungGen);
179 } // Else no need for a foreground young gc
180 assert((_gc_count_before < heap->total_collections()) ||
181 (GCLocker::is_active() /* gc may have been skipped */
182 && (_gc_count_before == heap->total_collections())),
183 "total_collections() should be monotonically increasing");
184
185 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
186 assert(_full_gc_count_before <= heap->total_full_collections(), "Error");
187 if (heap->total_full_collections() == _full_gc_count_before) {
188 // Nudge the CMS thread to start a concurrent collection.
189 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
190 } else {
191 assert(_full_gc_count_before < heap->total_full_collections(), "Error");
192 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
193 }
194 }
195
196 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
197 Thread* thr = Thread::current();
198 assert(thr != NULL, "Unexpected tid");
199 if (!thr->is_Java_thread()) {
200 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
201 CMSHeap* heap = CMSHeap::heap();
202 if (_gc_count_before != heap->total_collections()) {
203 // No need to do a young gc, we'll just nudge the CMS thread
204 // in the doit() method above, to be executed soon.
205 assert(_gc_count_before < heap->total_collections(),
206 "total_collections() should be monotonically increasing");
207 return false; // no need for foreground young gc
208 }
209 }
210 return true; // may still need foreground young gc
211 }
212
213
214 void VM_GenCollectFullConcurrent::doit_epilogue() {
215 Thread* thr = Thread::current();
216 assert(thr->is_Java_thread(), "just checking");
217 JavaThread* jt = (JavaThread*)thr;
218
219 if (Universe::has_reference_pending_list()) {
220 Heap_lock->notify_all();
221 }
222 Heap_lock->unlock();
223
224 // It is fine to test whether completed collections has
225 // exceeded our request count without locking because
226 // the completion count is monotonically increasing;
227 // this will break for very long-running apps when the
228 // count overflows and wraps around. XXX fix me !!!
229 // e.g. at the rate of 1 full gc per ms, this could
230 // overflow in about 1000 years.
231 CMSHeap* heap = CMSHeap::heap();
232 if (_gc_cause != GCCause::_gc_locker &&
233 heap->total_full_collections_completed() <= _full_gc_count_before) {
234 // maybe we should change the condition to test _gc_cause ==
235 // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run,
236 // instead of _gc_cause != GCCause::_gc_locker
237 assert(GCCause::is_user_requested_gc(_gc_cause),
238 "the only way to get here if this was a System.gc()-induced GC");
239 assert(ExplicitGCInvokesConcurrent, "Error");
240 // Now, wait for witnessing concurrent gc cycle to complete,
241 // but do so in native mode, because we want to lock the
242 // FullGCEvent_lock, which may be needed by the VM thread
243 // or by the CMS thread, so we do not want to be suspended
244 // while holding that lock.
245 ThreadToNativeFromVM native(jt);
246 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
247 // Either a concurrent or a stop-world full gc is sufficient
248 // witness to our request.
249 while (heap->total_full_collections_completed() <= _full_gc_count_before) {
250 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
251 }
252 }
253 }