1 /*
2 * Copyright (c) 2001, 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 "classfile/classLoaderDataGraph.hpp"
27 #include "gc/g1/g1Analytics.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1ConcurrentMark.inline.hpp"
30 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
31 #include "gc/g1/g1MMUTracker.hpp"
32 #include "gc/g1/g1Policy.hpp"
33 #include "gc/g1/g1RemSet.hpp"
34 #include "gc/g1/g1Trace.hpp"
35 #include "gc/g1/g1VMOperations.hpp"
36 #include "gc/shared/concurrentGCPhaseManager.hpp"
37 #include "gc/shared/gcId.hpp"
38 #include "gc/shared/gcTraceTime.inline.hpp"
39 #include "gc/shared/suspendibleThreadSet.hpp"
40 #include "logging/log.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "runtime/handles.inline.hpp"
43 #include "runtime/mutexLocker.inline.hpp"
44 #include "runtime/vmThread.hpp"
45 #include "utilities/debug.hpp"
46
47 // ======= Concurrent Mark Thread ========
48
49 // Check order in EXPAND_CURRENT_PHASES
50 STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE <
51 ConcurrentGCPhaseManager::IDLE_PHASE);
52
53 #define EXPAND_CONCURRENT_PHASES(expander) \
54 expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL) \
55 expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL) \
56 expander(CONCURRENT_CYCLE,, "Concurrent Cycle") \
57 expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks") \
58 expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions") \
59 expander(CONCURRENT_MARK,, "Concurrent Mark") \
60 expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots") \
61 expander(PRECLEAN,, "Concurrent Preclean") \
62 expander(BEFORE_REMARK,, NULL) \
63 expander(REMARK,, NULL) \
64 expander(REBUILD_REMEMBERED_SETS,, "Concurrent Rebuild Remembered Sets") \
65 expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark") \
66 /* */
67
68 class G1ConcurrentPhase : public AllStatic {
69 public:
70 enum {
71 #define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value,
72 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM)
73 #undef CONCURRENT_PHASE_ENUM
74 PHASE_ID_LIMIT
75 };
76 };
77
78 G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) :
79 ConcurrentGCThread(),
80 _vtime_start(0.0),
81 _vtime_accum(0.0),
82 _vtime_mark_accum(0.0),
83 _cm(cm),
84 _state(Idle),
85 _phase_manager_stack() {
86
87 set_name("G1 Main Marker");
88 create_and_start();
89 }
90
91 class CMRemark : public VoidClosure {
92 G1ConcurrentMark* _cm;
93 public:
94 CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
95
96 void do_void(){
97 _cm->remark();
98 }
99 };
100
101 class CMCleanup : public VoidClosure {
102 G1ConcurrentMark* _cm;
103 public:
104 CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
105
106 void do_void(){
107 _cm->cleanup();
108 }
109 };
110
111 double G1ConcurrentMarkThread::mmu_delay_end(G1Policy* g1_policy, bool remark) {
112 // There are 3 reasons to use SuspendibleThreadSetJoiner.
113 // 1. To avoid concurrency problem.
114 // - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
115 // concurrently from ConcurrentMarkThread and VMThread.
116 // 2. If currently a gc is running, but it has not yet updated the MMU,
117 // we will not forget to consider that pause in the MMU calculation.
118 // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
119 // And then sleep for predicted amount of time by delay_to_keep_mmu().
120 SuspendibleThreadSetJoiner sts_join;
121
122 const G1Analytics* analytics = g1_policy->analytics();
123 double prediction_ms = remark ? analytics->predict_remark_time_ms()
124 : analytics->predict_cleanup_time_ms();
125 double prediction = prediction_ms / MILLIUNITS;
126 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
127 double now = os::elapsedTime();
128 return now + mmu_tracker->when_sec(now, prediction);
129 }
130
131 void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
132 if (g1_policy->use_adaptive_young_list_length()) {
133 double delay_end_sec = mmu_delay_end(g1_policy, remark);
134 // Wait for timeout or thread termination request.
135 MonitorLocker ml(CGC_lock, Monitor::_no_safepoint_check_flag);
136 while (!_cm->has_aborted()) {
137 double sleep_time_sec = (delay_end_sec - os::elapsedTime());
138 jlong sleep_time_ms = ceil(sleep_time_sec * MILLIUNITS);
139 if (sleep_time_ms <= 0) {
140 break; // Passed end time.
141 } else if (ml.wait(sleep_time_ms, Monitor::_no_safepoint_check_flag)) {
142 break; // Timeout => reached end time.
143 } else if (should_terminate()) {
144 break; // Wakeup for pending termination request.
145 }
146 // Other (possibly spurious) wakeup. Retry with updated sleep time.
147 }
148 }
149 }
150
151 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
152 G1ConcurrentMark* _cm;
153
154 public:
155 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
156 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
157 _cm(cm)
158 {
159 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
160 }
161
162 ~G1ConcPhaseTimer() {
163 _cm->gc_timer_cm()->register_gc_concurrent_end();
164 }
165 };
166
167 static const char* const concurrent_phase_names[] = {
168 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
169 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
170 #undef CONCURRENT_PHASE_NAME
171 NULL // terminator
172 };
173 // Verify dense enum assumption. +1 for terminator.
174 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
175 ARRAY_SIZE(concurrent_phase_names));
176
177 // Returns the phase number for name, or a negative value if unknown.
178 static int lookup_concurrent_phase(const char* name) {
179 const char* const* names = concurrent_phase_names;
180 for (uint i = 0; names[i] != NULL; ++i) {
181 if (strcmp(name, names[i]) == 0) {
182 return static_cast<int>(i);
183 }
184 }
185 return -1;
186 }
187
188 // The phase must be valid and must have a title.
189 static const char* lookup_concurrent_phase_title(int phase) {
190 static const char* const titles[] = {
191 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
192 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
193 #undef CONCURRENT_PHASE_TITLE
194 };
195 // Verify dense enum assumption.
196 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
197
198 assert(0 <= phase, "precondition");
199 assert((uint)phase < ARRAY_SIZE(titles), "precondition");
200 const char* title = titles[phase];
201 assert(title != NULL, "precondition");
202 return title;
203 }
204
205 class G1ConcPhaseManager : public StackObj {
206 G1ConcurrentMark* _cm;
207 ConcurrentGCPhaseManager _manager;
208
209 public:
210 G1ConcPhaseManager(int phase, G1ConcurrentMarkThread* thread) :
211 _cm(thread->cm()),
212 _manager(phase, thread->phase_manager_stack())
213 { }
214
215 ~G1ConcPhaseManager() {
216 // Deactivate the manager if marking aborted, to avoid blocking on
217 // phase exit when the phase has been requested.
218 if (_cm->has_aborted()) {
219 _manager.deactivate();
220 }
221 }
222
223 void set_phase(int phase, bool force) {
224 _manager.set_phase(phase, force);
225 }
226 };
227
228 // Combine phase management and timing into one convenient utility.
229 class G1ConcPhase : public StackObj {
230 G1ConcPhaseTimer _timer;
231 G1ConcPhaseManager _manager;
232
233 public:
234 G1ConcPhase(int phase, G1ConcurrentMarkThread* thread) :
235 _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
236 _manager(phase, thread)
237 { }
238 };
239
240 bool G1ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
241 int phase = lookup_concurrent_phase(phase_name);
242 if (phase < 0) return false;
243
244 while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
245 phase_manager_stack())) {
246 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
247 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
248 // If idle and the goal is !idle, start a collection.
249 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
250 }
251 }
252 return true;
253 }
254
255 void G1ConcurrentMarkThread::run_service() {
256 _vtime_start = os::elapsedVTime();
257
258 G1CollectedHeap* g1h = G1CollectedHeap::heap();
259 G1Policy* policy = g1h->policy();
260
261 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
262
263 while (!should_terminate()) {
264 // wait until started is set.
265 sleep_before_next_cycle();
266 if (should_terminate()) {
267 break;
268 }
269
270 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
271
272 GCIdMark gc_id_mark;
273
274 _cm->concurrent_cycle_start();
275
276 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
277 {
278 ResourceMark rm;
279 HandleMark hm;
280 double cycle_start = os::elapsedVTime();
281
282 {
283 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
284 ClassLoaderDataGraph::clear_claimed_marks();
285 }
286
287 // We have to ensure that we finish scanning the root regions
288 // before the next GC takes place. To ensure this we have to
289 // make sure that we do not join the STS until the root regions
290 // have been scanned. If we did then it's possible that a
291 // subsequent GC could block us from joining the STS and proceed
292 // without the root regions have been scanned which would be a
293 // correctness issue.
294
295 {
296 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
297 _cm->scan_root_regions();
298 }
299
300 // It would be nice to use the G1ConcPhase class here but
301 // the "end" logging is inside the loop and not at the end of
302 // a scope. Also, the timer doesn't support nesting.
303 // Mimicking the same log output instead.
304 {
305 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
306 jlong mark_start = os::elapsed_counter();
307 const char* cm_title = lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
308 log_info(gc, marking)("%s (%.3fs)",
309 cm_title,
310 TimeHelper::counter_to_seconds(mark_start));
311 for (uint iter = 1; !_cm->has_aborted(); ++iter) {
312 // Concurrent marking.
313 {
314 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
315 _cm->mark_from_roots();
316 }
317 if (_cm->has_aborted()) {
318 break;
319 }
320
321 if (G1UseReferencePrecleaning) {
322 G1ConcPhase p(G1ConcurrentPhase::PRECLEAN, this);
323 _cm->preclean();
324 }
325
326 // Provide a control point before remark.
327 {
328 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
329 }
330 if (_cm->has_aborted()) {
331 break;
332 }
333
334 // Delay remark pause for MMU.
335 double mark_end_time = os::elapsedVTime();
336 jlong mark_end = os::elapsed_counter();
337 _vtime_mark_accum += (mark_end_time - cycle_start);
338 delay_to_keep_mmu(policy, true /* remark */);
339 if (_cm->has_aborted()) {
340 break;
341 }
342
343 // Pause Remark.
344 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
345 cm_title,
346 TimeHelper::counter_to_seconds(mark_start),
347 TimeHelper::counter_to_seconds(mark_end),
348 TimeHelper::counter_to_millis(mark_end - mark_start));
349 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
350 CMRemark cl(_cm);
351 VM_G1Concurrent op(&cl, "Pause Remark");
352 VMThread::execute(&op);
353 if (_cm->has_aborted()) {
354 break;
355 } else if (!_cm->restart_for_overflow()) {
356 break; // Exit loop if no restart requested.
357 } else {
358 // Loop to restart for overflow.
359 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
360 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
361 cm_title, iter);
362 }
363 }
364 }
365
366 if (!_cm->has_aborted()) {
367 G1ConcPhase p(G1ConcurrentPhase::REBUILD_REMEMBERED_SETS, this);
368 _cm->rebuild_rem_set_concurrently();
369 }
370
371 double end_time = os::elapsedVTime();
372 // Update the total virtual time before doing this, since it will try
373 // to measure it to get the vtime for this marking.
374 _vtime_accum = (end_time - _vtime_start);
375
376 if (!_cm->has_aborted()) {
377 delay_to_keep_mmu(policy, false /* cleanup */);
378 }
379
380 if (!_cm->has_aborted()) {
381 CMCleanup cl_cl(_cm);
382 VM_G1Concurrent op(&cl_cl, "Pause Cleanup");
383 VMThread::execute(&op);
384 }
385
386 // We now want to allow clearing of the marking bitmap to be
387 // suspended by a collection pause.
388 // We may have aborted just before the remark. Do not bother clearing the
389 // bitmap then, as it has been done during mark abort.
390 if (!_cm->has_aborted()) {
391 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
392 _cm->cleanup_for_next_mark();
393 }
394 }
395
396 // Update the number of full collections that have been
397 // completed. This will also notify the FullGCCount_lock in case a
398 // Java thread is waiting for a full GC to happen (e.g., it
399 // called System.gc() with +ExplicitGCInvokesConcurrent).
400 {
401 SuspendibleThreadSetJoiner sts_join;
402 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
403
404 _cm->concurrent_cycle_end();
405 }
406
407 cpmanager.set_phase(G1ConcurrentPhase::IDLE, _cm->has_aborted() /* force */);
408 }
409 _cm->root_regions()->cancel_scan();
410 }
411
412 void G1ConcurrentMarkThread::stop_service() {
413 MutexLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
414 CGC_lock->notify_all();
415 }
416
417
418 void G1ConcurrentMarkThread::sleep_before_next_cycle() {
419 // We join here because we don't want to do the "shouldConcurrentMark()"
420 // below while the world is otherwise stopped.
421 assert(!in_progress(), "should have been cleared");
422
423 MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
424 while (!started() && !should_terminate()) {
425 ml.wait();
426 }
427
428 if (started()) {
429 set_in_progress();
430 }
431 }