1/*
2 * Copyright (c) 2005, 2019, 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/cmsVMOperations.hpp"
28#include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
29#include "gc/cms/concurrentMarkSweepThread.hpp"
30#include "gc/shared/gcLocker.hpp"
31#include "gc/shared/gcTimer.hpp"
32#include "gc/shared/gcTraceTime.inline.hpp"
33#include "gc/shared/isGCActiveMark.hpp"
34#include "memory/universe.hpp"
35#include "runtime/handles.inline.hpp"
36#include "runtime/interfaceSupport.inline.hpp"
37#include "runtime/os.hpp"
38#include "utilities/dtrace.hpp"
39
40//////////////////////////////////////////////////////////
41// Methods in abstract class VM_CMS_Operation
42//////////////////////////////////////////////////////////
43void VM_CMS_Operation::verify_before_gc() {
44 if (VerifyBeforeGC &&
45 CMSHeap::heap()->total_collections() >= VerifyGCStartAt) {
46 GCTraceTime(Info, gc, phases, verify) tm("Verify Before", _collector->_gc_timer_cm);
47 HandleMark hm;
48 FreelistLocker x(_collector);
49 MutexLocker y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
50 CMSHeap::heap()->prepare_for_verify();
51 Universe::verify();
52 }
53}
54
55void VM_CMS_Operation::verify_after_gc() {
56 if (VerifyAfterGC &&
57 CMSHeap::heap()->total_collections() >= VerifyGCStartAt) {
58 GCTraceTime(Info, gc, phases, verify) tm("Verify After", _collector->_gc_timer_cm);
59 HandleMark hm;
60 FreelistLocker x(_collector);
61 MutexLocker y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
62 Universe::verify();
63 }
64}
65
66bool VM_CMS_Operation::lost_race() const {
67 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
68 // We lost a race to a foreground collection
69 // -- there's nothing to do
70 return true;
71 }
72 assert(CMSCollector::abstract_state() == legal_state(),
73 "Inconsistent collector state?");
74 return false;
75}
76
77bool VM_CMS_Operation::doit_prologue() {
78 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
79 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
80 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
81 "Possible deadlock");
82
83 Heap_lock->lock();
84 if (lost_race()) {
85 assert(_prologue_succeeded == false, "Initialized in c'tor");
86 Heap_lock->unlock();
87 } else {
88 _prologue_succeeded = true;
89 }
90 return _prologue_succeeded;
91}
92
93void VM_CMS_Operation::doit_epilogue() {
94 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
95 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
96 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
97 "Possible deadlock");
98
99 if (Universe::has_reference_pending_list()) {
100 Heap_lock->notify_all();
101 }
102 Heap_lock->unlock();
103}
104
105//////////////////////////////////////////////////////////
106// Methods in class VM_CMS_Initial_Mark
107//////////////////////////////////////////////////////////
108void VM_CMS_Initial_Mark::doit() {
109 if (lost_race()) {
110 // Nothing to do.
111 return;
112 }
113 HS_PRIVATE_CMS_INITMARK_BEGIN();
114 GCIdMark gc_id_mark(_gc_id);
115
116 _collector->_gc_timer_cm->register_gc_pause_start("Initial Mark");
117
118 CMSHeap* heap = CMSHeap::heap();
119 GCCauseSetter gccs(heap, GCCause::_cms_initial_mark);
120
121 VM_CMS_Operation::verify_before_gc();
122
123 IsGCActiveMark x; // stop-world GC active
124 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial, heap->gc_cause());
125
126 VM_CMS_Operation::verify_after_gc();
127
128 _collector->_gc_timer_cm->register_gc_pause_end();
129
130 HS_PRIVATE_CMS_INITMARK_END();
131}
132
133//////////////////////////////////////////////////////////
134// Methods in class VM_CMS_Final_Remark_Operation
135//////////////////////////////////////////////////////////
136void VM_CMS_Final_Remark::doit() {
137 if (lost_race()) {
138 // Nothing to do.
139 return;
140 }
141 HS_PRIVATE_CMS_REMARK_BEGIN();
142 GCIdMark gc_id_mark(_gc_id);
143
144 _collector->_gc_timer_cm->register_gc_pause_start("Final Mark");
145
146 CMSHeap* heap = CMSHeap::heap();
147 GCCauseSetter gccs(heap, GCCause::_cms_final_remark);
148
149 VM_CMS_Operation::verify_before_gc();
150
151 IsGCActiveMark x; // stop-world GC active
152 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal, heap->gc_cause());
153
154 VM_CMS_Operation::verify_after_gc();
155
156 _collector->save_heap_summary();
157 _collector->_gc_timer_cm->register_gc_pause_end();
158
159 HS_PRIVATE_CMS_REMARK_END();
160}
161
162// VM operation to invoke a concurrent collection of a
163// GenCollectedHeap heap.
164void VM_GenCollectFullConcurrent::doit() {
165 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
166 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
167
168 CMSHeap* heap = CMSHeap::heap();
169 if (_gc_count_before == heap->total_collections()) {
170 // The "full" of do_full_collection call below "forces"
171 // a collection; the second arg, 0, below ensures that
172 // only the young gen is collected. XXX In the future,
173 // we'll probably need to have something in this interface
174 // to say do this only if we are sure we will not bail
175 // out to a full collection in this attempt, but that's
176 // for the future.
177 assert(SafepointSynchronize::is_at_safepoint(),
178 "We can only be executing this arm of if at a safepoint");
179 GCCauseSetter gccs(heap, _gc_cause);
180 heap->do_full_collection(heap->must_clear_all_soft_refs(), GenCollectedHeap::YoungGen);
181 } // Else no need for a foreground young gc
182 assert((_gc_count_before < heap->total_collections()) ||
183 (GCLocker::is_active() /* gc may have been skipped */
184 && (_gc_count_before == heap->total_collections())),
185 "total_collections() should be monotonically increasing");
186
187 MutexLocker x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
188 assert(_full_gc_count_before <= heap->total_full_collections(), "Error");
189 if (heap->total_full_collections() == _full_gc_count_before) {
190 // Nudge the CMS thread to start a concurrent collection.
191 CMSCollector::request_full_gc(_full_gc_count_before, _gc_cause);
192 } else {
193 assert(_full_gc_count_before < heap->total_full_collections(), "Error");
194 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
195 }
196}
197
198bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
199 Thread* thr = Thread::current();
200 assert(thr != NULL, "Unexpected tid");
201 if (!thr->is_Java_thread()) {
202 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
203 CMSHeap* heap = CMSHeap::heap();
204 if (_gc_count_before != heap->total_collections()) {
205 // No need to do a young gc, we'll just nudge the CMS thread
206 // in the doit() method above, to be executed soon.
207 assert(_gc_count_before < heap->total_collections(),
208 "total_collections() should be monotonically increasing");
209 return false; // no need for foreground young gc
210 }
211 }
212 return true; // may still need foreground young gc
213}
214
215
216void VM_GenCollectFullConcurrent::doit_epilogue() {
217 Thread* thr = Thread::current();
218 assert(thr->is_Java_thread(), "just checking");
219 JavaThread* jt = (JavaThread*)thr;
220
221 if (Universe::has_reference_pending_list()) {
222 Heap_lock->notify_all();
223 }
224 Heap_lock->unlock();
225
226 // It is fine to test whether completed collections has
227 // exceeded our request count without locking because
228 // the completion count is monotonically increasing;
229 // this will break for very long-running apps when the
230 // count overflows and wraps around. XXX fix me !!!
231 // e.g. at the rate of 1 full gc per ms, this could
232 // overflow in about 1000 years.
233 CMSHeap* heap = CMSHeap::heap();
234 if (_gc_cause != GCCause::_gc_locker &&
235 heap->total_full_collections_completed() <= _full_gc_count_before) {
236 // maybe we should change the condition to test _gc_cause ==
237 // GCCause::_java_lang_system_gc or GCCause::_dcmd_gc_run,
238 // instead of _gc_cause != GCCause::_gc_locker
239 assert(GCCause::is_user_requested_gc(_gc_cause),
240 "the only way to get here if this was a System.gc()-induced GC");
241 assert(ExplicitGCInvokesConcurrent, "Error");
242 // Now, wait for witnessing concurrent gc cycle to complete,
243 // but do so in native mode, because we want to lock the
244 // FullGCEvent_lock, which may be needed by the VM thread
245 // or by the CMS thread, so we do not want to be suspended
246 // while holding that lock.
247 ThreadToNativeFromVM native(jt);
248 MutexLocker ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
249 // Either a concurrent or a stop-world full gc is sufficient
250 // witness to our request.
251 while (heap->total_full_collections_completed() <= _full_gc_count_before) {
252 FullGCCount_lock->wait_without_safepoint_check();
253 }
254 }
255}
256