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/classLoaderData.hpp"
27 #include "gc/g1/concurrentMarkThread.inline.hpp"
28 #include "gc/g1/g1Analytics.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1ConcurrentMark.inline.hpp"
31 #include "gc/g1/g1MMUTracker.hpp"
32 #include "gc/g1/g1Policy.hpp"
33 #include "gc/g1/vm_operations_g1.hpp"
34 #include "gc/shared/concurrentGCPhaseManager.hpp"
35 #include "gc/shared/gcId.hpp"
36 #include "gc/shared/gcTrace.hpp"
37 #include "gc/shared/gcTraceTime.inline.hpp"
38 #include "gc/shared/suspendibleThreadSet.hpp"
39 #include "logging/log.hpp"
40 #include "memory/resourceArea.hpp"
41 #include "runtime/vmThread.hpp"
42 #include "utilities/debug.hpp"
43
44 // ======= Concurrent Mark Thread ========
45
46 // Check order in EXPAND_CURRENT_PHASES
47 STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE <
48 ConcurrentGCPhaseManager::IDLE_PHASE);
49
50 #define EXPAND_CONCURRENT_PHASES(expander) \
51 expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL) \
52 expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL) \
53 expander(CONCURRENT_CYCLE,, "Concurrent Cycle") \
54 expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks") \
55 expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions") \
56 expander(CONCURRENT_MARK,, "Concurrent Mark") \
57 expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots") \
58 expander(BEFORE_REMARK,, NULL) \
59 expander(REMARK,, NULL) \
60 expander(CREATE_LIVE_DATA,, "Concurrent Create Live Data") \
61 expander(COMPLETE_CLEANUP,, "Concurrent Complete Cleanup") \
62 expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark") \
63 /* */
64
65 class G1ConcurrentPhase : public AllStatic {
66 public:
67 enum {
68 #define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value,
69 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM)
70 #undef CONCURRENT_PHASE_ENUM
71 PHASE_ID_LIMIT
72 };
73 };
74
75 // The CM thread is created when the G1 garbage collector is used
76
77 ConcurrentMarkThread::ConcurrentMarkThread(G1ConcurrentMark* cm) :
78 ConcurrentGCThread(),
79 _cm(cm),
80 _state(Idle),
81 _phase_manager_stack(),
82 _vtime_accum(0.0),
83 _vtime_mark_accum(0.0) {
84
85 set_name("G1 Main Marker");
86 create_and_start();
87 }
88
89 class CMCheckpointRootsFinalClosure: public VoidClosure {
90
91 G1ConcurrentMark* _cm;
92 public:
93
94 CMCheckpointRootsFinalClosure(G1ConcurrentMark* cm) :
95 _cm(cm) {}
96
97 void do_void(){
98 _cm->checkpoint_roots_final(false); // !clear_all_soft_refs
99 }
100 };
101
102 class CMCleanUp: public VoidClosure {
103 G1ConcurrentMark* _cm;
104 public:
105
106 CMCleanUp(G1ConcurrentMark* cm) :
107 _cm(cm) {}
108
109 void do_void(){
110 _cm->cleanup();
111 }
112 };
113
114 double ConcurrentMarkThread::mmu_sleep_time(G1Policy* g1_policy, bool remark) {
115 // There are 3 reasons to use SuspendibleThreadSetJoiner.
116 // 1. To avoid concurrency problem.
117 // - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
118 // concurrently from ConcurrentMarkThread and VMThread.
119 // 2. If currently a gc is running, but it has not yet updated the MMU,
120 // we will not forget to consider that pause in the MMU calculation.
121 // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
122 // And then sleep for predicted amount of time by delay_to_keep_mmu().
123 SuspendibleThreadSetJoiner sts_join;
124
125 const G1Analytics* analytics = g1_policy->analytics();
126 double now = os::elapsedTime();
127 double prediction_ms = remark ? analytics->predict_remark_time_ms()
128 : analytics->predict_cleanup_time_ms();
129 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
130 return mmu_tracker->when_ms(now, prediction_ms);
131 }
132
133 void ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
134 if (g1_policy->adaptive_young_list_length()) {
135 jlong sleep_time_ms = mmu_sleep_time(g1_policy, remark);
136 if (!cm()->has_aborted() && sleep_time_ms > 0) {
137 os::sleep(this, sleep_time_ms, false);
138 }
139 }
140 }
141
142 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
143 G1ConcurrentMark* _cm;
144
145 public:
146 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
147 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
148 _cm(cm)
149 {
150 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
151 }
152
153 ~G1ConcPhaseTimer() {
154 _cm->gc_timer_cm()->register_gc_concurrent_end();
155 }
156 };
157
158 static const char* const concurrent_phase_names[] = {
159 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
160 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
161 #undef CONCURRENT_PHASE_NAME
162 NULL // terminator
163 };
164 // Verify dense enum assumption. +1 for terminator.
165 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
166 ARRAY_SIZE(concurrent_phase_names));
167
168 // Returns the phase number for name, or a negative value if unknown.
169 static int lookup_concurrent_phase(const char* name) {
170 const char* const* names = concurrent_phase_names;
171 for (uint i = 0; names[i] != NULL; ++i) {
172 if (strcmp(name, names[i]) == 0) {
173 return static_cast<int>(i);
174 }
175 }
176 return -1;
177 }
178
179 // The phase must be valid and must have a title.
180 static const char* lookup_concurrent_phase_title(int phase) {
181 static const char* const titles[] = {
182 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
183 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
184 #undef CONCURRENT_PHASE_TITLE
185 };
186 // Verify dense enum assumption.
187 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
188
189 assert(0 <= phase, "precondition");
190 assert((uint)phase < ARRAY_SIZE(titles), "precondition");
191 const char* title = titles[phase];
192 assert(title != NULL, "precondition");
193 return title;
194 }
195
196 class G1ConcPhaseManager : public StackObj {
197 G1ConcurrentMark* _cm;
198 ConcurrentGCPhaseManager _manager;
199
200 public:
201 G1ConcPhaseManager(int phase, ConcurrentMarkThread* thread) :
202 _cm(thread->cm()),
203 _manager(phase, thread->phase_manager_stack())
204 { }
205
206 ~G1ConcPhaseManager() {
207 // Deactivate the manager if marking aborted, to avoid blocking on
208 // phase exit when the phase has been requested.
209 if (_cm->has_aborted()) {
210 _manager.deactivate();
211 }
212 }
213
214 void set_phase(int phase, bool force) {
215 _manager.set_phase(phase, force);
216 }
217 };
218
219 // Combine phase management and timing into one convenient utility.
220 class G1ConcPhase : public StackObj {
221 G1ConcPhaseTimer _timer;
222 G1ConcPhaseManager _manager;
223
224 public:
225 G1ConcPhase(int phase, ConcurrentMarkThread* thread) :
226 _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
227 _manager(phase, thread)
228 { }
229 };
230
231 const char* const* ConcurrentMarkThread::concurrent_phases() const {
232 return concurrent_phase_names;
233 }
234
235 bool ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
236 int phase = lookup_concurrent_phase(phase_name);
237 if (phase < 0) return false;
238
239 while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
240 phase_manager_stack())) {
241 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
242 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
243 // If idle and the goal is !idle, start a collection.
244 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
245 }
246 }
247 return true;
248 }
249
250 void ConcurrentMarkThread::run_service() {
251 _vtime_start = os::elapsedVTime();
252
253 G1CollectedHeap* g1h = G1CollectedHeap::heap();
254 G1Policy* g1_policy = g1h->g1_policy();
255
256 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
257
258 while (!should_terminate()) {
259 // wait until started is set.
260 sleepBeforeNextCycle();
261 if (should_terminate()) {
262 break;
263 }
264
265 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
266
267 GCIdMark gc_id_mark;
268
269 cm()->concurrent_cycle_start();
270
271 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
272 {
273 ResourceMark rm;
274 HandleMark hm;
275 double cycle_start = os::elapsedVTime();
276
277 {
278 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
279 ClassLoaderDataGraph::clear_claimed_marks();
280 }
281
282 // We have to ensure that we finish scanning the root regions
283 // before the next GC takes place. To ensure this we have to
284 // make sure that we do not join the STS until the root regions
285 // have been scanned. If we did then it's possible that a
286 // subsequent GC could block us from joining the STS and proceed
287 // without the root regions have been scanned which would be a
288 // correctness issue.
289
290 {
291 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
292 _cm->scan_root_regions();
293 }
294
295 // It would be nice to use the G1ConcPhase class here but
296 // the "end" logging is inside the loop and not at the end of
297 // a scope. Also, the timer doesn't support nesting.
298 // Mimicking the same log output instead.
299 {
300 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
301 jlong mark_start = os::elapsed_counter();
302 const char* cm_title =
303 lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
304 log_info(gc, marking)("%s (%.3fs)",
305 cm_title,
306 TimeHelper::counter_to_seconds(mark_start));
307 for (uint iter = 1; !cm()->has_aborted(); ++iter) {
308 // Concurrent marking.
309 {
310 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
311 _cm->mark_from_roots();
312 }
313 if (cm()->has_aborted()) break;
314
315 // Provide a control point after mark_from_roots.
316 {
317 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
318 }
319 if (cm()->has_aborted()) break;
320
321 // Delay remark pause for MMU.
322 double mark_end_time = os::elapsedVTime();
323 jlong mark_end = os::elapsed_counter();
324 _vtime_mark_accum += (mark_end_time - cycle_start);
325 delay_to_keep_mmu(g1_policy, true /* remark */);
326 if (cm()->has_aborted()) break;
327
328 // Pause Remark.
329 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
330 cm_title,
331 TimeHelper::counter_to_seconds(mark_start),
332 TimeHelper::counter_to_seconds(mark_end),
333 TimeHelper::counter_to_millis(mark_end - mark_start));
334 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
335 CMCheckpointRootsFinalClosure final_cl(_cm);
336 VM_CGC_Operation op(&final_cl, "Pause Remark");
337 VMThread::execute(&op);
338 if (cm()->has_aborted()) {
339 break;
340 } else if (!cm()->restart_for_overflow()) {
341 break; // Exit loop if no restart requested.
342 } else {
343 // Loop to restart for overflow.
344 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
345 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
346 cm_title, iter);
347 }
348 }
349 }
350
351 if (!cm()->has_aborted()) {
352 G1ConcPhase p(G1ConcurrentPhase::CREATE_LIVE_DATA, this);
353 cm()->create_live_data();
354 }
355
356 double end_time = os::elapsedVTime();
357 // Update the total virtual time before doing this, since it will try
358 // to measure it to get the vtime for this marking. We purposely
359 // neglect the presumably-short "completeCleanup" phase here.
360 _vtime_accum = (end_time - _vtime_start);
361
362 if (!cm()->has_aborted()) {
363 delay_to_keep_mmu(g1_policy, false /* cleanup */);
364
365 if (!cm()->has_aborted()) {
366 CMCleanUp cl_cl(_cm);
367 VM_CGC_Operation op(&cl_cl, "Pause Cleanup");
368 VMThread::execute(&op);
369 }
370 } else {
371 // We don't want to update the marking status if a GC pause
372 // is already underway.
373 SuspendibleThreadSetJoiner sts_join;
374 g1h->collector_state()->set_mark_in_progress(false);
375 }
376
377 // Check if cleanup set the free_regions_coming flag. If it
378 // hasn't, we can just skip the next step.
379 if (g1h->free_regions_coming()) {
380 // The following will finish freeing up any regions that we
381 // found to be empty during cleanup. We'll do this part
382 // without joining the suspendible set. If an evacuation pause
383 // takes place, then we would carry on freeing regions in
384 // case they are needed by the pause. If a Full GC takes
385 // place, it would wait for us to process the regions
386 // reclaimed by cleanup.
387
388 // Now do the concurrent cleanup operation.
389 G1ConcPhase p(G1ConcurrentPhase::COMPLETE_CLEANUP, this);
390 _cm->complete_cleanup();
391
392 // Notify anyone who's waiting that there are no more free
393 // regions coming. We have to do this before we join the STS
394 // (in fact, we should not attempt to join the STS in the
395 // interval between finishing the cleanup pause and clearing
396 // the free_regions_coming flag) otherwise we might deadlock:
397 // a GC worker could be blocked waiting for the notification
398 // whereas this thread will be blocked for the pause to finish
399 // while it's trying to join the STS, which is conditional on
400 // the GC workers finishing.
401 g1h->reset_free_regions_coming();
402 }
403 guarantee(cm()->cleanup_list_is_empty(),
404 "at this point there should be no regions on the cleanup list");
405
406 // There is a tricky race before recording that the concurrent
407 // cleanup has completed and a potential Full GC starting around
408 // the same time. We want to make sure that the Full GC calls
409 // abort() on concurrent mark after
410 // record_concurrent_mark_cleanup_completed(), since abort() is
411 // the method that will reset the concurrent mark state. If we
412 // end up calling record_concurrent_mark_cleanup_completed()
413 // after abort() then we might incorrectly undo some of the work
414 // abort() did. Checking the has_aborted() flag after joining
415 // the STS allows the correct ordering of the two methods. There
416 // are two scenarios:
417 //
418 // a) If we reach here before the Full GC, the fact that we have
419 // joined the STS means that the Full GC cannot start until we
420 // leave the STS, so record_concurrent_mark_cleanup_completed()
421 // will complete before abort() is called.
422 //
423 // b) If we reach here during the Full GC, we'll be held up from
424 // joining the STS until the Full GC is done, which means that
425 // abort() will have completed and has_aborted() will return
426 // true to prevent us from calling
427 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
428 // not needed any more as the concurrent mark state has been
429 // already reset).
430 {
431 SuspendibleThreadSetJoiner sts_join;
432 if (!cm()->has_aborted()) {
433 g1_policy->record_concurrent_mark_cleanup_completed();
434 } else {
435 log_info(gc, marking)("Concurrent Mark Abort");
436 }
437 }
438
439 // We now want to allow clearing of the marking bitmap to be
440 // suspended by a collection pause.
441 // We may have aborted just before the remark. Do not bother clearing the
442 // bitmap then, as it has been done during mark abort.
443 if (!cm()->has_aborted()) {
444 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
445 _cm->cleanup_for_next_mark();
446 } else {
447 assert(!G1VerifyBitmaps || _cm->next_mark_bitmap_is_clear(), "Next mark bitmap must be clear");
448 }
449 }
450
451 // Update the number of full collections that have been
452 // completed. This will also notify the FullGCCount_lock in case a
453 // Java thread is waiting for a full GC to happen (e.g., it
454 // called System.gc() with +ExplicitGCInvokesConcurrent).
455 {
456 SuspendibleThreadSetJoiner sts_join;
457 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
458
459 cm()->concurrent_cycle_end();
460 }
461
462 cpmanager.set_phase(G1ConcurrentPhase::IDLE, cm()->has_aborted() /* force */);
463 }
464 _cm->root_regions()->cancel_scan();
465 }
466
467 void ConcurrentMarkThread::stop_service() {
468 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
469 CGC_lock->notify_all();
470 }
471
472 void ConcurrentMarkThread::sleepBeforeNextCycle() {
473 // We join here because we don't want to do the "shouldConcurrentMark()"
474 // below while the world is otherwise stopped.
475 assert(!in_progress(), "should have been cleared");
476
477 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
478 while (!started() && !should_terminate()) {
479 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
480 }
481
482 if (started()) {
483 set_in_progress();
484 }
485 }