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