1 /*
2 * Copyright (c) 2001, 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/g1/concurrentMarkThread.inline.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
29 #include "gc_implementation/g1/g1MMUTracker.hpp"
30 #include "gc_implementation/g1/vm_operations_g1.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "runtime/vmThread.hpp"
33
34 // ======= Concurrent Mark Thread ========
35
36 // The CM thread is created when the G1 garbage collector is used
37
38 SurrogateLockerThread*
39 ConcurrentMarkThread::_slt = NULL;
40
41 ConcurrentMarkThread::ConcurrentMarkThread(ConcurrentMark* cm) :
42 ConcurrentGCThread(),
43 _cm(cm),
44 _started(false),
45 _in_progress(false),
46 _vtime_accum(0.0),
47 _vtime_mark_accum(0.0)
48 {
49 create_and_start();
50 }
51
52 class CMCheckpointRootsFinalClosure: public VoidClosure {
53
54 ConcurrentMark* _cm;
55 public:
56
57 CMCheckpointRootsFinalClosure(ConcurrentMark* cm) :
58 _cm(cm) {}
59
60 void do_void(){
61 _cm->checkpointRootsFinal(false); // !clear_all_soft_refs
62 }
63 };
64
65 class CMCleanUp: public VoidClosure {
66 ConcurrentMark* _cm;
67 public:
68
69 CMCleanUp(ConcurrentMark* cm) :
70 _cm(cm) {}
71
72 void do_void(){
73 _cm->cleanup();
74 }
75 };
76
77
78
79 void ConcurrentMarkThread::run() {
80 initialize_in_thread();
81 _vtime_start = os::elapsedVTime();
82 wait_for_universe_init();
83
84 G1CollectedHeap* g1h = G1CollectedHeap::heap();
85 G1CollectorPolicy* g1_policy = g1h->g1_policy();
86 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
87 Thread *current_thread = Thread::current();
88
89 while (!_should_terminate) {
90 // wait until started is set.
91 sleepBeforeNextCycle();
92 {
93 ResourceMark rm;
94 HandleMark hm;
95 double cycle_start = os::elapsedVTime();
96 double mark_start_sec = os::elapsedTime();
97 char verbose_str[128];
98
99 if (PrintGC) {
100 gclog_or_tty->date_stamp(PrintGCDateStamps);
101 gclog_or_tty->stamp(PrintGCTimeStamps);
102 gclog_or_tty->print_cr("[GC concurrent-mark-start]");
103 }
104
105 int iter = 0;
106 do {
107 iter++;
108 if (!cm()->has_aborted()) {
109 _cm->markFromRoots();
110 }
111
112 double mark_end_time = os::elapsedVTime();
113 double mark_end_sec = os::elapsedTime();
114 _vtime_mark_accum += (mark_end_time - cycle_start);
115 if (!cm()->has_aborted()) {
116 if (g1_policy->adaptive_young_list_length()) {
117 double now = os::elapsedTime();
118 double remark_prediction_ms = g1_policy->predict_remark_time_ms();
119 jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms);
120 os::sleep(current_thread, sleep_time_ms, false);
121 }
122
123 if (PrintGC) {
124 gclog_or_tty->date_stamp(PrintGCDateStamps);
125 gclog_or_tty->stamp(PrintGCTimeStamps);
126 gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf sec]",
127 mark_end_sec - mark_start_sec);
128 }
129
130 CMCheckpointRootsFinalClosure final_cl(_cm);
131 sprintf(verbose_str, "GC remark");
132 VM_CGC_Operation op(&final_cl, verbose_str);
133 VMThread::execute(&op);
134 }
135 if (cm()->restart_for_overflow() &&
136 G1TraceMarkStackOverflow) {
137 gclog_or_tty->print_cr("Restarting conc marking because of MS overflow "
138 "in remark (restart #%d).", iter);
139 }
140
141 if (cm()->restart_for_overflow()) {
142 if (PrintGC) {
143 gclog_or_tty->date_stamp(PrintGCDateStamps);
144 gclog_or_tty->stamp(PrintGCTimeStamps);
145 gclog_or_tty->print_cr("[GC concurrent-mark-restart-for-overflow]");
146 }
147 }
148 } while (cm()->restart_for_overflow());
149
150 double end_time = os::elapsedVTime();
151 // Update the total virtual time before doing this, since it will try
152 // to measure it to get the vtime for this marking. We purposely
153 // neglect the presumably-short "completeCleanup" phase here.
154 _vtime_accum = (end_time - _vtime_start);
155
156 if (!cm()->has_aborted()) {
157 if (g1_policy->adaptive_young_list_length()) {
158 double now = os::elapsedTime();
159 double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms();
160 jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms);
161 os::sleep(current_thread, sleep_time_ms, false);
162 }
163
164 CMCleanUp cl_cl(_cm);
165 sprintf(verbose_str, "GC cleanup");
166 VM_CGC_Operation op(&cl_cl, verbose_str);
167 VMThread::execute(&op);
168 } else {
169 // We don't want to update the marking status if a GC pause
170 // is already underway.
171 _sts.join();
172 g1h->set_marking_complete();
173 _sts.leave();
174 }
175
176 // Check if cleanup set the free_regions_coming flag. If it
177 // hasn't, we can just skip the next step.
178 if (g1h->free_regions_coming()) {
179 // The following will finish freeing up any regions that we
180 // found to be empty during cleanup. We'll do this part
181 // without joining the suspendible set. If an evacuation pause
182 // takes place, then we would carry on freeing regions in
183 // case they are needed by the pause. If a Full GC takes
184 // place, it would wait for us to process the regions
185 // reclaimed by cleanup.
186
187 double cleanup_start_sec = os::elapsedTime();
188 if (PrintGC) {
189 gclog_or_tty->date_stamp(PrintGCDateStamps);
190 gclog_or_tty->stamp(PrintGCTimeStamps);
191 gclog_or_tty->print_cr("[GC concurrent-cleanup-start]");
192 }
193
194 // Now do the concurrent cleanup operation.
195 _cm->completeCleanup();
196
197 // Notify anyone who's waiting that there are no more free
198 // regions coming. We have to do this before we join the STS
199 // (in fact, we should not attempt to join the STS in the
200 // interval between finishing the cleanup pause and clearing
201 // the free_regions_coming flag) otherwise we might deadlock:
202 // a GC worker could be blocked waiting for the notification
203 // whereas this thread will be blocked for the pause to finish
204 // while it's trying to join the STS, which is conditional on
205 // the GC workers finishing.
206 g1h->reset_free_regions_coming();
207
208 double cleanup_end_sec = os::elapsedTime();
209 if (PrintGC) {
210 gclog_or_tty->date_stamp(PrintGCDateStamps);
211 gclog_or_tty->stamp(PrintGCTimeStamps);
212 gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf]",
213 cleanup_end_sec - cleanup_start_sec);
214 }
215 }
216 guarantee(cm()->cleanup_list_is_empty(),
217 "at this point there should be no regions on the cleanup list");
218
219 // There is a tricky race before recording that the concurrent
220 // cleanup has completed and a potential Full GC starting around
221 // the same time. We want to make sure that the Full GC calls
222 // abort() on concurrent mark after
223 // record_concurrent_mark_cleanup_completed(), since abort() is
224 // the method that will reset the concurrent mark state. If we
225 // end up calling record_concurrent_mark_cleanup_completed()
226 // after abort() then we might incorrectly undo some of the work
227 // abort() did. Checking the has_aborted() flag after joining
228 // the STS allows the correct ordering of the two methods. There
229 // are two scenarios:
230 //
231 // a) If we reach here before the Full GC, the fact that we have
232 // joined the STS means that the Full GC cannot start until we
233 // leave the STS, so record_concurrent_mark_cleanup_completed()
234 // will complete before abort() is called.
235 //
236 // b) If we reach here during the Full GC, we'll be held up from
237 // joining the STS until the Full GC is done, which means that
238 // abort() will have completed and has_aborted() will return
239 // true to prevent us from calling
240 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
241 // not needed any more as the concurrent mark state has been
242 // already reset).
243 _sts.join();
244 if (!cm()->has_aborted()) {
245 g1_policy->record_concurrent_mark_cleanup_completed();
246 }
247 _sts.leave();
248
249 if (cm()->has_aborted()) {
250 if (PrintGC) {
251 gclog_or_tty->date_stamp(PrintGCDateStamps);
252 gclog_or_tty->stamp(PrintGCTimeStamps);
253 gclog_or_tty->print_cr("[GC concurrent-mark-abort]");
254 }
255 }
256
257 // We now want to allow clearing of the marking bitmap to be
258 // suspended by a collection pause.
259 _sts.join();
260 _cm->clearNextBitmap();
261 _sts.leave();
262 }
263
264 // Update the number of full collections that have been
265 // completed. This will also notify the FullGCCount_lock in case a
266 // Java thread is waiting for a full GC to happen (e.g., it
267 // called System.gc() with +ExplicitGCInvokesConcurrent).
268 _sts.join();
269 g1h->increment_full_collections_completed(true /* concurrent */);
270 _sts.leave();
271 }
272 assert(_should_terminate, "just checking");
273
274 terminate();
275 }
276
277
278 void ConcurrentMarkThread::yield() {
279 _sts.yield("Concurrent Mark");
280 }
281
282 void ConcurrentMarkThread::stop() {
283 // it is ok to take late safepoints here, if needed
284 MutexLockerEx mu(Terminator_lock);
285 _should_terminate = true;
286 while (!_has_terminated) {
287 Terminator_lock->wait();
288 }
289 }
290
291 void ConcurrentMarkThread::print() const {
292 print_on(tty);
293 }
294
295 void ConcurrentMarkThread::print_on(outputStream* st) const {
296 st->print("\"G1 Main Concurrent Mark GC Thread\" ");
297 Thread::print_on(st);
298 st->cr();
299 }
300
301 void ConcurrentMarkThread::sleepBeforeNextCycle() {
302 // We join here because we don't want to do the "shouldConcurrentMark()"
303 // below while the world is otherwise stopped.
304 assert(!in_progress(), "should have been cleared");
305
306 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
307 while (!started()) {
308 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
309 }
310 set_in_progress();
311 clear_started();
312 }
313
314 // Note: As is the case with CMS - this method, although exported
315 // by the ConcurrentMarkThread, which is a non-JavaThread, can only
316 // be called by a JavaThread. Currently this is done at vm creation
317 // time (post-vm-init) by the main/Primordial (Java)Thread.
318 // XXX Consider changing this in the future to allow the CM thread
319 // itself to create this thread?
320 void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) {
321 assert(UseG1GC, "SLT thread needed only for concurrent GC");
322 assert(THREAD->is_Java_thread(), "must be a Java thread");
323 assert(_slt == NULL, "SLT already created");
324 _slt = SurrogateLockerThread::make(THREAD);
325 }