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 _vtime_count_accum(0.0)
49 {
50 create_and_start();
51 }
52
53 class CMCheckpointRootsFinalClosure: public VoidClosure {
54
55 ConcurrentMark* _cm;
56 public:
57
58 CMCheckpointRootsFinalClosure(ConcurrentMark* cm) :
59 _cm(cm) {}
60
61 void do_void(){
62 _cm->checkpointRootsFinal(false); // !clear_all_soft_refs
63 }
64 };
65
66 class CMCleanUp: public VoidClosure {
67 ConcurrentMark* _cm;
68 public:
69
70 CMCleanUp(ConcurrentMark* cm) :
71 _cm(cm) {}
72
73 void do_void(){
74 _cm->cleanup();
75 }
76 };
77
78
79
80 void ConcurrentMarkThread::run() {
81 initialize_in_thread();
82 _vtime_start = os::elapsedVTime();
83 wait_for_universe_init();
84
85 G1CollectedHeap* g1h = G1CollectedHeap::heap();
86 G1CollectorPolicy* g1_policy = g1h->g1_policy();
87 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
88 Thread *current_thread = Thread::current();
89
90 while (!_should_terminate) {
91 // wait until started is set.
92 sleepBeforeNextCycle();
93 {
94 ResourceMark rm;
95 HandleMark hm;
96 double cycle_start = os::elapsedVTime();
97 double mark_start_sec = os::elapsedTime();
98 char verbose_str[128];
99
100 if (PrintGC) {
101 gclog_or_tty->date_stamp(PrintGCDateStamps);
102 gclog_or_tty->stamp(PrintGCTimeStamps);
103 gclog_or_tty->print_cr("[GC concurrent-mark-start]");
104 }
105
106 int iter = 0;
107 do {
108 iter++;
109 if (!cm()->has_aborted()) {
110 _cm->markFromRoots();
111 }
112
113 double mark_end_time = os::elapsedVTime();
114 double mark_end_sec = os::elapsedTime();
115 _vtime_mark_accum += (mark_end_time - cycle_start);
116 if (!cm()->has_aborted()) {
117 if (g1_policy->adaptive_young_list_length()) {
118 double now = os::elapsedTime();
119 double remark_prediction_ms = g1_policy->predict_remark_time_ms();
120 jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms);
121 os::sleep(current_thread, sleep_time_ms, false);
122 }
123
124 if (PrintGC) {
125 gclog_or_tty->date_stamp(PrintGCDateStamps);
126 gclog_or_tty->stamp(PrintGCTimeStamps);
127 gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf sec]",
128 mark_end_sec - mark_start_sec);
129 }
130
131 CMCheckpointRootsFinalClosure final_cl(_cm);
132 sprintf(verbose_str, "GC remark");
133 VM_CGC_Operation op(&final_cl, verbose_str);
134 VMThread::execute(&op);
135 }
136 if (cm()->restart_for_overflow() &&
137 G1TraceMarkStackOverflow) {
138 gclog_or_tty->print_cr("Restarting conc marking because of MS overflow "
139 "in remark (restart #%d).", iter);
140 }
141
142 if (cm()->restart_for_overflow()) {
143 if (PrintGC) {
144 gclog_or_tty->date_stamp(PrintGCDateStamps);
145 gclog_or_tty->stamp(PrintGCTimeStamps);
146 gclog_or_tty->print_cr("[GC concurrent-mark-restart-for-overflow]");
147 }
148 }
149 } while (cm()->restart_for_overflow());
150
151 double counting_start_time = os::elapsedVTime();
152 if (!cm()->has_aborted()) {
153 double count_start_sec = os::elapsedTime();
154 if (PrintGC) {
155 gclog_or_tty->date_stamp(PrintGCDateStamps);
156 gclog_or_tty->stamp(PrintGCTimeStamps);
157 gclog_or_tty->print_cr("[GC concurrent-count-start]");
158 }
159
160 _sts.join();
161 _cm->calcDesiredRegions();
162 _sts.leave();
163
164 if (!cm()->has_aborted()) {
165 double count_end_sec = os::elapsedTime();
166 if (PrintGC) {
167 gclog_or_tty->date_stamp(PrintGCDateStamps);
168 gclog_or_tty->stamp(PrintGCTimeStamps);
169 gclog_or_tty->print_cr("[GC concurrent-count-end, %1.7lf]",
170 count_end_sec - count_start_sec);
171 }
172 }
173 }
174
175 double end_time = os::elapsedVTime();
176 _vtime_count_accum += (end_time - counting_start_time);
177 // Update the total virtual time before doing this, since it will try
178 // to measure it to get the vtime for this marking. We purposely
179 // neglect the presumably-short "completeCleanup" phase here.
180 _vtime_accum = (end_time - _vtime_start);
181 if (!cm()->has_aborted()) {
182 if (g1_policy->adaptive_young_list_length()) {
183 double now = os::elapsedTime();
184 double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms();
185 jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms);
186 os::sleep(current_thread, sleep_time_ms, false);
187 }
188
189 CMCleanUp cl_cl(_cm);
190 sprintf(verbose_str, "GC cleanup");
191 VM_CGC_Operation op(&cl_cl, verbose_str);
192 VMThread::execute(&op);
193 } else {
194 // We don't want to update the marking status if a GC pause
195 // is already underway.
196 _sts.join();
197 g1h->set_marking_complete();
198 _sts.leave();
199 }
200
201 // Check if cleanup set the free_regions_coming flag. If it
202 // hasn't, we can just skip the next step.
203 if (g1h->free_regions_coming()) {
204 // The following will finish freeing up any regions that we
205 // found to be empty during cleanup. We'll do this part
206 // without joining the suspendible set. If an evacuation pause
207 // takes place, then we would carry on freeing regions in
208 // case they are needed by the pause. If a Full GC takes
209 // place, it would wait for us to process the regions
210 // reclaimed by cleanup.
211
212 double cleanup_start_sec = os::elapsedTime();
213 if (PrintGC) {
214 gclog_or_tty->date_stamp(PrintGCDateStamps);
215 gclog_or_tty->stamp(PrintGCTimeStamps);
216 gclog_or_tty->print_cr("[GC concurrent-cleanup-start]");
217 }
218
219 // Now do the concurrent cleanup operation.
220 _cm->completeCleanup();
221
222 // Notify anyone who's waiting that there are no more free
223 // regions coming. We have to do this before we join the STS
224 // (in fact, we should not attempt to join the STS in the
225 // interval between finishing the cleanup pause and clearing
226 // the free_regions_coming flag) otherwise we might deadlock:
227 // a GC worker could be blocked waiting for the notification
228 // whereas this thread will be blocked for the pause to finish
229 // while it's trying to join the STS, which is conditional on
230 // the GC workers finishing.
231 g1h->reset_free_regions_coming();
232
233 double cleanup_end_sec = os::elapsedTime();
234 if (PrintGC) {
235 gclog_or_tty->date_stamp(PrintGCDateStamps);
236 gclog_or_tty->stamp(PrintGCTimeStamps);
237 gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf]",
238 cleanup_end_sec - cleanup_start_sec);
239 }
240 }
241 guarantee(cm()->cleanup_list_is_empty(),
242 "at this point there should be no regions on the cleanup list");
243
244 // There is a tricky race before recording that the concurrent
245 // cleanup has completed and a potential Full GC starting around
246 // the same time. We want to make sure that the Full GC calls
247 // abort() on concurrent mark after
248 // record_concurrent_mark_cleanup_completed(), since abort() is
249 // the method that will reset the concurrent mark state. If we
250 // end up calling record_concurrent_mark_cleanup_completed()
251 // after abort() then we might incorrectly undo some of the work
252 // abort() did. Checking the has_aborted() flag after joining
253 // the STS allows the correct ordering of the two methods. There
254 // are two scenarios:
255 //
256 // a) If we reach here before the Full GC, the fact that we have
257 // joined the STS means that the Full GC cannot start until we
258 // leave the STS, so record_concurrent_mark_cleanup_completed()
259 // will complete before abort() is called.
260 //
261 // b) If we reach here during the Full GC, we'll be held up from
262 // joining the STS until the Full GC is done, which means that
263 // abort() will have completed and has_aborted() will return
264 // true to prevent us from calling
265 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
266 // not needed any more as the concurrent mark state has been
267 // already reset).
268 _sts.join();
269 if (!cm()->has_aborted()) {
270 g1_policy->record_concurrent_mark_cleanup_completed();
271 }
272 _sts.leave();
273
274 if (cm()->has_aborted()) {
275 if (PrintGC) {
276 gclog_or_tty->date_stamp(PrintGCDateStamps);
277 gclog_or_tty->stamp(PrintGCTimeStamps);
278 gclog_or_tty->print_cr("[GC concurrent-mark-abort]");
279 }
280 }
281
282 // We now want to allow clearing of the marking bitmap to be
283 // suspended by a collection pause.
284 _sts.join();
285 _cm->clearNextBitmap();
286 _sts.leave();
287 }
288
289 // Update the number of full collections that have been
290 // completed. This will also notify the FullGCCount_lock in case a
291 // Java thread is waiting for a full GC to happen (e.g., it
292 // called System.gc() with +ExplicitGCInvokesConcurrent).
293 _sts.join();
294 g1h->increment_full_collections_completed(true /* concurrent */);
295 _sts.leave();
296 }
297 assert(_should_terminate, "just checking");
298
299 terminate();
300 }
301
302
303 void ConcurrentMarkThread::yield() {
304 _sts.yield("Concurrent Mark");
305 }
306
307 void ConcurrentMarkThread::stop() {
308 // it is ok to take late safepoints here, if needed
309 MutexLockerEx mu(Terminator_lock);
310 _should_terminate = true;
311 while (!_has_terminated) {
312 Terminator_lock->wait();
313 }
314 }
315
316 void ConcurrentMarkThread::print() const {
317 print_on(tty);
318 }
319
320 void ConcurrentMarkThread::print_on(outputStream* st) const {
321 st->print("\"G1 Main Concurrent Mark GC Thread\" ");
322 Thread::print_on(st);
323 st->cr();
324 }
325
326 void ConcurrentMarkThread::sleepBeforeNextCycle() {
327 // We join here because we don't want to do the "shouldConcurrentMark()"
328 // below while the world is otherwise stopped.
329 assert(!in_progress(), "should have been cleared");
330
331 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
332 while (!started()) {
333 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
334 }
335 set_in_progress();
336 clear_started();
337 }
338
339 // Note: As is the case with CMS - this method, although exported
340 // by the ConcurrentMarkThread, which is a non-JavaThread, can only
341 // be called by a JavaThread. Currently this is done at vm creation
342 // time (post-vm-init) by the main/Primordial (Java)Thread.
343 // XXX Consider changing this in the future to allow the CM thread
344 // itself to create this thread?
345 void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) {
346 assert(UseG1GC, "SLT thread needed only for concurrent GC");
347 assert(THREAD->is_Java_thread(), "must be a Java thread");
348 assert(_slt == NULL, "SLT already created");
349 _slt = SurrogateLockerThread::make(THREAD);
350 }