1 /*
2 * Copyright (c) 2001, 2018, 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/g1VMOperations.hpp"
35 #include "gc/shared/concurrentGCPhaseManager.hpp"
36 #include "gc/shared/gcId.hpp"
37 #include "gc/shared/gcTrace.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
G1ConcurrentMarkThread(G1ConcurrentMark * cm)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:
CMRemark(G1ConcurrentMark * cm)93 CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
94
do_void()95 void do_void(){
96 _cm->remark();
97 }
98 };
99
100 class CMCleanup : public VoidClosure {
101 G1ConcurrentMark* _cm;
102 public:
CMCleanup(G1ConcurrentMark * cm)103 CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
104
do_void()105 void do_void(){
106 _cm->cleanup();
107 }
108 };
109
mmu_sleep_time(G1Policy * g1_policy,bool remark)110 double G1ConcurrentMarkThread::mmu_sleep_time(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 now = os::elapsedTime();
123 double prediction_ms = remark ? analytics->predict_remark_time_ms()
124 : analytics->predict_cleanup_time_ms();
125 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
126 return mmu_tracker->when_ms(now, prediction_ms);
127 }
128
delay_to_keep_mmu(G1Policy * g1_policy,bool remark)129 void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
130 if (g1_policy->adaptive_young_list_length()) {
131 jlong sleep_time_ms = mmu_sleep_time(g1_policy, remark);
132 if (!_cm->has_aborted() && sleep_time_ms > 0) {
133 os::sleep(this, sleep_time_ms, false);
134 }
135 }
136 }
137
138 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
139 G1ConcurrentMark* _cm;
140
141 public:
G1ConcPhaseTimer(G1ConcurrentMark * cm,const char * title)142 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
143 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
144 _cm(cm)
145 {
146 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
147 }
148
~G1ConcPhaseTimer()149 ~G1ConcPhaseTimer() {
150 _cm->gc_timer_cm()->register_gc_concurrent_end();
151 }
152 };
153
154 static const char* const concurrent_phase_names[] = {
155 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
156 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
157 #undef CONCURRENT_PHASE_NAME
158 NULL // terminator
159 };
160 // Verify dense enum assumption. +1 for terminator.
161 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
162 ARRAY_SIZE(concurrent_phase_names));
163
164 // Returns the phase number for name, or a negative value if unknown.
lookup_concurrent_phase(const char * name)165 static int lookup_concurrent_phase(const char* name) {
166 const char* const* names = concurrent_phase_names;
167 for (uint i = 0; names[i] != NULL; ++i) {
168 if (strcmp(name, names[i]) == 0) {
169 return static_cast<int>(i);
170 }
171 }
172 return -1;
173 }
174
175 // The phase must be valid and must have a title.
lookup_concurrent_phase_title(int phase)176 static const char* lookup_concurrent_phase_title(int phase) {
177 static const char* const titles[] = {
178 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
179 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
180 #undef CONCURRENT_PHASE_TITLE
181 };
182 // Verify dense enum assumption.
183 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
184
185 assert(0 <= phase, "precondition");
186 assert((uint)phase < ARRAY_SIZE(titles), "precondition");
187 const char* title = titles[phase];
188 assert(title != NULL, "precondition");
189 return title;
190 }
191
192 class G1ConcPhaseManager : public StackObj {
193 G1ConcurrentMark* _cm;
194 ConcurrentGCPhaseManager _manager;
195
196 public:
G1ConcPhaseManager(int phase,G1ConcurrentMarkThread * thread)197 G1ConcPhaseManager(int phase, G1ConcurrentMarkThread* thread) :
198 _cm(thread->cm()),
199 _manager(phase, thread->phase_manager_stack())
200 { }
201
~G1ConcPhaseManager()202 ~G1ConcPhaseManager() {
203 // Deactivate the manager if marking aborted, to avoid blocking on
204 // phase exit when the phase has been requested.
205 if (_cm->has_aborted()) {
206 _manager.deactivate();
207 }
208 }
209
set_phase(int phase,bool force)210 void set_phase(int phase, bool force) {
211 _manager.set_phase(phase, force);
212 }
213 };
214
215 // Combine phase management and timing into one convenient utility.
216 class G1ConcPhase : public StackObj {
217 G1ConcPhaseTimer _timer;
218 G1ConcPhaseManager _manager;
219
220 public:
G1ConcPhase(int phase,G1ConcurrentMarkThread * thread)221 G1ConcPhase(int phase, G1ConcurrentMarkThread* thread) :
222 _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
223 _manager(phase, thread)
224 { }
225 };
226
concurrent_phases() const227 const char* const* G1ConcurrentMarkThread::concurrent_phases() const {
228 return concurrent_phase_names;
229 }
230
request_concurrent_phase(const char * phase_name)231 bool G1ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
232 int phase = lookup_concurrent_phase(phase_name);
233 if (phase < 0) return false;
234
235 while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
236 phase_manager_stack())) {
237 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
238 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
239 // If idle and the goal is !idle, start a collection.
240 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
241 }
242 }
243 return true;
244 }
245
run_service()246 void G1ConcurrentMarkThread::run_service() {
247 _vtime_start = os::elapsedVTime();
248
249 G1CollectedHeap* g1h = G1CollectedHeap::heap();
250 G1Policy* g1_policy = g1h->g1_policy();
251
252 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
253
254 while (!should_terminate()) {
255 // wait until started is set.
256 sleep_before_next_cycle();
257 if (should_terminate()) {
258 break;
259 }
260
261 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
262
263 GCIdMark gc_id_mark;
264
265 _cm->concurrent_cycle_start();
266
267 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
268 {
269 ResourceMark rm;
270 HandleMark hm;
271 double cycle_start = os::elapsedVTime();
272
273 {
274 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
275 ClassLoaderDataGraph::clear_claimed_marks();
276 }
277
278 // We have to ensure that we finish scanning the root regions
279 // before the next GC takes place. To ensure this we have to
280 // make sure that we do not join the STS until the root regions
281 // have been scanned. If we did then it's possible that a
282 // subsequent GC could block us from joining the STS and proceed
283 // without the root regions have been scanned which would be a
284 // correctness issue.
285
286 {
287 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
288 _cm->scan_root_regions();
289 }
290
291 // It would be nice to use the G1ConcPhase class here but
292 // the "end" logging is inside the loop and not at the end of
293 // a scope. Also, the timer doesn't support nesting.
294 // Mimicking the same log output instead.
295 {
296 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
297 jlong mark_start = os::elapsed_counter();
298 const char* cm_title = lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
299 log_info(gc, marking)("%s (%.3fs)",
300 cm_title,
301 TimeHelper::counter_to_seconds(mark_start));
302 for (uint iter = 1; !_cm->has_aborted(); ++iter) {
303 // Concurrent marking.
304 {
305 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
306 _cm->mark_from_roots();
307 }
308 if (_cm->has_aborted()) {
309 break;
310 }
311
312 if (G1UseReferencePrecleaning) {
313 G1ConcPhase p(G1ConcurrentPhase::PRECLEAN, this);
314 _cm->preclean();
315 }
316
317 // Provide a control point before remark.
318 {
319 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
320 }
321 if (_cm->has_aborted()) {
322 break;
323 }
324
325 // Delay remark pause for MMU.
326 double mark_end_time = os::elapsedVTime();
327 jlong mark_end = os::elapsed_counter();
328 _vtime_mark_accum += (mark_end_time - cycle_start);
329 delay_to_keep_mmu(g1_policy, true /* remark */);
330 if (_cm->has_aborted()) {
331 break;
332 }
333
334 // Pause Remark.
335 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
336 cm_title,
337 TimeHelper::counter_to_seconds(mark_start),
338 TimeHelper::counter_to_seconds(mark_end),
339 TimeHelper::counter_to_millis(mark_end - mark_start));
340 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
341 CMRemark cl(_cm);
342 VM_G1Concurrent op(&cl, "Pause Remark");
343 VMThread::execute(&op);
344 if (_cm->has_aborted()) {
345 break;
346 } else if (!_cm->restart_for_overflow()) {
347 break; // Exit loop if no restart requested.
348 } else {
349 // Loop to restart for overflow.
350 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
351 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
352 cm_title, iter);
353 }
354 }
355 }
356
357 if (!_cm->has_aborted()) {
358 G1ConcPhase p(G1ConcurrentPhase::REBUILD_REMEMBERED_SETS, this);
359 _cm->rebuild_rem_set_concurrently();
360 }
361
362 double end_time = os::elapsedVTime();
363 // Update the total virtual time before doing this, since it will try
364 // to measure it to get the vtime for this marking.
365 _vtime_accum = (end_time - _vtime_start);
366
367 if (!_cm->has_aborted()) {
368 delay_to_keep_mmu(g1_policy, false /* cleanup */);
369 }
370
371 if (!_cm->has_aborted()) {
372 CMCleanup cl_cl(_cm);
373 VM_G1Concurrent op(&cl_cl, "Pause Cleanup");
374 VMThread::execute(&op);
375 }
376
377 // We now want to allow clearing of the marking bitmap to be
378 // suspended by a collection pause.
379 // We may have aborted just before the remark. Do not bother clearing the
380 // bitmap then, as it has been done during mark abort.
381 if (!_cm->has_aborted()) {
382 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
383 _cm->cleanup_for_next_mark();
384 }
385 }
386
387 // Update the number of full collections that have been
388 // completed. This will also notify the FullGCCount_lock in case a
389 // Java thread is waiting for a full GC to happen (e.g., it
390 // called System.gc() with +ExplicitGCInvokesConcurrent).
391 {
392 SuspendibleThreadSetJoiner sts_join;
393 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
394
395 _cm->concurrent_cycle_end();
396 }
397
398 cpmanager.set_phase(G1ConcurrentPhase::IDLE, _cm->has_aborted() /* force */);
399 }
400 _cm->root_regions()->cancel_scan();
401 }
402
stop_service()403 void G1ConcurrentMarkThread::stop_service() {
404 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
405 CGC_lock->notify_all();
406 }
407
408
sleep_before_next_cycle()409 void G1ConcurrentMarkThread::sleep_before_next_cycle() {
410 // We join here because we don't want to do the "shouldConcurrentMark()"
411 // below while the world is otherwise stopped.
412 assert(!in_progress(), "should have been cleared");
413
414 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
415 while (!started() && !should_terminate()) {
416 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
417 }
418
419 if (started()) {
420 set_in_progress();
421 }
422 }
423