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/handles.inline.hpp"
42 #include "runtime/vmThread.hpp"
43 #include "utilities/debug.hpp"
44
45 // ======= Concurrent Mark Thread ========
46
47 // Check order in EXPAND_CURRENT_PHASES
48 STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE <
49 ConcurrentGCPhaseManager::IDLE_PHASE);
50
51 #define EXPAND_CONCURRENT_PHASES(expander) \
52 expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL) \
53 expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL) \
54 expander(CONCURRENT_CYCLE,, "Concurrent Cycle") \
55 expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks") \
56 expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions") \
57 expander(CONCURRENT_MARK,, "Concurrent Mark") \
58 expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots") \
59 expander(BEFORE_REMARK,, NULL) \
60 expander(REMARK,, NULL) \
61 expander(CREATE_LIVE_DATA,, "Concurrent Create Live Data") \
62 expander(COMPLETE_CLEANUP,, "Concurrent Complete Cleanup") \
63 expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark") \
64 /* */
65
66 class G1ConcurrentPhase : public AllStatic {
67 public:
68 enum {
69 #define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value,
70 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM)
71 #undef CONCURRENT_PHASE_ENUM
72 PHASE_ID_LIMIT
73 };
74 };
75
76 // The CM thread is created when the G1 garbage collector is used
77
78 ConcurrentMarkThread::ConcurrentMarkThread(G1ConcurrentMark* cm) :
79 ConcurrentGCThread(),
80 _cm(cm),
81 _state(Idle),
82 _phase_manager_stack(),
83 _vtime_accum(0.0),
84 _vtime_mark_accum(0.0) {
85
86 set_name("G1 Main Marker");
87 create_and_start();
88 }
89
90 class CMCheckpointRootsFinalClosure: public VoidClosure {
91
92 G1ConcurrentMark* _cm;
93 public:
94
95 CMCheckpointRootsFinalClosure(G1ConcurrentMark* cm) :
96 _cm(cm) {}
97
98 void do_void(){
99 _cm->checkpoint_roots_final(false); // !clear_all_soft_refs
100 }
101 };
102
103 class CMCleanUp: public VoidClosure {
104 G1ConcurrentMark* _cm;
105 public:
106
107 CMCleanUp(G1ConcurrentMark* cm) :
108 _cm(cm) {}
109
110 void do_void(){
111 _cm->cleanup();
112 }
113 };
114
115 double ConcurrentMarkThread::mmu_sleep_time(G1Policy* g1_policy, bool remark) {
116 // There are 3 reasons to use SuspendibleThreadSetJoiner.
117 // 1. To avoid concurrency problem.
118 // - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
119 // concurrently from ConcurrentMarkThread and VMThread.
120 // 2. If currently a gc is running, but it has not yet updated the MMU,
121 // we will not forget to consider that pause in the MMU calculation.
122 // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
123 // And then sleep for predicted amount of time by delay_to_keep_mmu().
124 SuspendibleThreadSetJoiner sts_join;
125
126 const G1Analytics* analytics = g1_policy->analytics();
127 double now = os::elapsedTime();
128 double prediction_ms = remark ? analytics->predict_remark_time_ms()
129 : analytics->predict_cleanup_time_ms();
130 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
131 return mmu_tracker->when_ms(now, prediction_ms);
132 }
133
134 void ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
135 if (g1_policy->adaptive_young_list_length()) {
136 jlong sleep_time_ms = mmu_sleep_time(g1_policy, remark);
137 if (!cm()->has_aborted() && sleep_time_ms > 0) {
138 os::sleep(this, sleep_time_ms, false);
139 }
140 }
141 }
142
143 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
144 G1ConcurrentMark* _cm;
145
146 public:
147 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
148 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
149 _cm(cm)
150 {
151 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
152 }
153
154 ~G1ConcPhaseTimer() {
155 _cm->gc_timer_cm()->register_gc_concurrent_end();
156 }
157 };
158
159 static const char* const concurrent_phase_names[] = {
160 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
161 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
162 #undef CONCURRENT_PHASE_NAME
163 NULL // terminator
164 };
165 // Verify dense enum assumption. +1 for terminator.
166 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
167 ARRAY_SIZE(concurrent_phase_names));
168
169 // Returns the phase number for name, or a negative value if unknown.
170 static int lookup_concurrent_phase(const char* name) {
171 const char* const* names = concurrent_phase_names;
172 for (uint i = 0; names[i] != NULL; ++i) {
173 if (strcmp(name, names[i]) == 0) {
174 return static_cast<int>(i);
175 }
176 }
177 return -1;
178 }
179
180 // The phase must be valid and must have a title.
181 static const char* lookup_concurrent_phase_title(int phase) {
182 static const char* const titles[] = {
183 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
184 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
185 #undef CONCURRENT_PHASE_TITLE
186 };
187 // Verify dense enum assumption.
188 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
189
190 assert(0 <= phase, "precondition");
191 assert((uint)phase < ARRAY_SIZE(titles), "precondition");
192 const char* title = titles[phase];
193 assert(title != NULL, "precondition");
194 return title;
195 }
196
197 class G1ConcPhaseManager : public StackObj {
198 G1ConcurrentMark* _cm;
199 ConcurrentGCPhaseManager _manager;
200
201 public:
202 G1ConcPhaseManager(int phase, ConcurrentMarkThread* thread) :
203 _cm(thread->cm()),
204 _manager(phase, thread->phase_manager_stack())
205 { }
206
207 ~G1ConcPhaseManager() {
208 // Deactivate the manager if marking aborted, to avoid blocking on
209 // phase exit when the phase has been requested.
210 if (_cm->has_aborted()) {
211 _manager.deactivate();
212 }
213 }
214
215 void set_phase(int phase, bool force) {
216 _manager.set_phase(phase, force);
217 }
218 };
219
220 // Combine phase management and timing into one convenient utility.
221 class G1ConcPhase : public StackObj {
222 G1ConcPhaseTimer _timer;
223 G1ConcPhaseManager _manager;
224
225 public:
226 G1ConcPhase(int phase, ConcurrentMarkThread* thread) :
227 _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
228 _manager(phase, thread)
229 { }
230 };
231
232 const char* const* ConcurrentMarkThread::concurrent_phases() const {
233 return concurrent_phase_names;
234 }
235
236 bool ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
237 int phase = lookup_concurrent_phase(phase_name);
238 if (phase < 0) return false;
239
240 while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
241 phase_manager_stack())) {
242 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
243 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
244 // If idle and the goal is !idle, start a collection.
245 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
246 }
247 }
248 return true;
249 }
250
251 void ConcurrentMarkThread::run_service() {
252 _vtime_start = os::elapsedVTime();
253
254 G1CollectedHeap* g1h = G1CollectedHeap::heap();
255 G1Policy* g1_policy = g1h->g1_policy();
256
257 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
258
259 while (!should_terminate()) {
260 // wait until started is set.
261 sleepBeforeNextCycle();
262 if (should_terminate()) {
263 break;
264 }
265
266 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
267
268 GCIdMark gc_id_mark;
269
270 cm()->concurrent_cycle_start();
271
272 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
273 {
274 ResourceMark rm;
275 HandleMark hm;
276 double cycle_start = os::elapsedVTime();
277
278 {
279 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
280 ClassLoaderDataGraph::clear_claimed_marks();
281 }
282
283 // We have to ensure that we finish scanning the root regions
284 // before the next GC takes place. To ensure this we have to
285 // make sure that we do not join the STS until the root regions
286 // have been scanned. If we did then it's possible that a
287 // subsequent GC could block us from joining the STS and proceed
288 // without the root regions have been scanned which would be a
289 // correctness issue.
290
291 {
292 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
293 _cm->scan_root_regions();
294 }
295
296 // It would be nice to use the G1ConcPhase class here but
297 // the "end" logging is inside the loop and not at the end of
298 // a scope. Also, the timer doesn't support nesting.
299 // Mimicking the same log output instead.
300 {
301 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
302 jlong mark_start = os::elapsed_counter();
303 const char* cm_title =
304 lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
305 log_info(gc, marking)("%s (%.3fs)",
306 cm_title,
307 TimeHelper::counter_to_seconds(mark_start));
308 for (uint iter = 1; !cm()->has_aborted(); ++iter) {
309 // Concurrent marking.
310 {
311 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
312 _cm->mark_from_roots();
313 }
314 if (cm()->has_aborted()) break;
315
316 // Provide a control point after mark_from_roots.
317 {
318 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
319 }
320 if (cm()->has_aborted()) break;
321
322 // Delay remark pause for MMU.
323 double mark_end_time = os::elapsedVTime();
324 jlong mark_end = os::elapsed_counter();
325 _vtime_mark_accum += (mark_end_time - cycle_start);
326 delay_to_keep_mmu(g1_policy, true /* remark */);
327 if (cm()->has_aborted()) break;
328
329 // Pause Remark.
330 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
331 cm_title,
332 TimeHelper::counter_to_seconds(mark_start),
333 TimeHelper::counter_to_seconds(mark_end),
334 TimeHelper::counter_to_millis(mark_end - mark_start));
335 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
336 CMCheckpointRootsFinalClosure final_cl(_cm);
337 VM_CGC_Operation op(&final_cl, "Pause Remark");
338 VMThread::execute(&op);
339 if (cm()->has_aborted()) {
340 break;
341 } else if (!cm()->restart_for_overflow()) {
342 break; // Exit loop if no restart requested.
343 } else {
344 // Loop to restart for overflow.
345 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
346 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
347 cm_title, iter);
348 }
349 }
350 }
351
352 if (!cm()->has_aborted()) {
353 G1ConcPhase p(G1ConcurrentPhase::CREATE_LIVE_DATA, this);
354 cm()->create_live_data();
355 }
356
357 double end_time = os::elapsedVTime();
358 // Update the total virtual time before doing this, since it will try
359 // to measure it to get the vtime for this marking. We purposely
360 // neglect the presumably-short "completeCleanup" phase here.
361 _vtime_accum = (end_time - _vtime_start);
362
363 if (!cm()->has_aborted()) {
364 delay_to_keep_mmu(g1_policy, false /* cleanup */);
365
366 if (!cm()->has_aborted()) {
367 CMCleanUp cl_cl(_cm);
368 VM_CGC_Operation op(&cl_cl, "Pause Cleanup");
369 VMThread::execute(&op);
370 }
371 } else {
372 // We don't want to update the marking status if a GC pause
373 // is already underway.
374 SuspendibleThreadSetJoiner sts_join;
375 g1h->collector_state()->set_mark_in_progress(false);
376 }
377
378 // Check if cleanup set the free_regions_coming flag. If it
379 // hasn't, we can just skip the next step.
380 if (g1h->free_regions_coming()) {
381 // The following will finish freeing up any regions that we
382 // found to be empty during cleanup. We'll do this part
383 // without joining the suspendible set. If an evacuation pause
384 // takes place, then we would carry on freeing regions in
385 // case they are needed by the pause. If a Full GC takes
386 // place, it would wait for us to process the regions
387 // reclaimed by cleanup.
388
389 // Now do the concurrent cleanup operation.
390 G1ConcPhase p(G1ConcurrentPhase::COMPLETE_CLEANUP, this);
391 _cm->complete_cleanup();
392
393 // Notify anyone who's waiting that there are no more free
394 // regions coming. We have to do this before we join the STS
395 // (in fact, we should not attempt to join the STS in the
396 // interval between finishing the cleanup pause and clearing
397 // the free_regions_coming flag) otherwise we might deadlock:
398 // a GC worker could be blocked waiting for the notification
399 // whereas this thread will be blocked for the pause to finish
400 // while it's trying to join the STS, which is conditional on
401 // the GC workers finishing.
402 g1h->reset_free_regions_coming();
403 }
404 guarantee(cm()->cleanup_list_is_empty(),
405 "at this point there should be no regions on the cleanup list");
406
407 // There is a tricky race before recording that the concurrent
408 // cleanup has completed and a potential Full GC starting around
409 // the same time. We want to make sure that the Full GC calls
410 // abort() on concurrent mark after
411 // record_concurrent_mark_cleanup_completed(), since abort() is
412 // the method that will reset the concurrent mark state. If we
413 // end up calling record_concurrent_mark_cleanup_completed()
414 // after abort() then we might incorrectly undo some of the work
415 // abort() did. Checking the has_aborted() flag after joining
416 // the STS allows the correct ordering of the two methods. There
417 // are two scenarios:
418 //
419 // a) If we reach here before the Full GC, the fact that we have
420 // joined the STS means that the Full GC cannot start until we
421 // leave the STS, so record_concurrent_mark_cleanup_completed()
422 // will complete before abort() is called.
423 //
424 // b) If we reach here during the Full GC, we'll be held up from
425 // joining the STS until the Full GC is done, which means that
426 // abort() will have completed and has_aborted() will return
427 // true to prevent us from calling
428 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
429 // not needed any more as the concurrent mark state has been
430 // already reset).
431 {
432 SuspendibleThreadSetJoiner sts_join;
433 if (!cm()->has_aborted()) {
434 g1_policy->record_concurrent_mark_cleanup_completed();
435 } else {
436 log_info(gc, marking)("Concurrent Mark Abort");
437 }
438 }
439
440 // We now want to allow clearing of the marking bitmap to be
441 // suspended by a collection pause.
442 // We may have aborted just before the remark. Do not bother clearing the
443 // bitmap then, as it has been done during mark abort.
444 if (!cm()->has_aborted()) {
445 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
446 _cm->cleanup_for_next_mark();
447 } else {
448 assert(!G1VerifyBitmaps || _cm->next_mark_bitmap_is_clear(), "Next mark bitmap must be clear");
449 }
450 }
451
452 // Update the number of full collections that have been
453 // completed. This will also notify the FullGCCount_lock in case a
454 // Java thread is waiting for a full GC to happen (e.g., it
455 // called System.gc() with +ExplicitGCInvokesConcurrent).
456 {
457 SuspendibleThreadSetJoiner sts_join;
458 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
459
460 cm()->concurrent_cycle_end();
461 }
462
463 cpmanager.set_phase(G1ConcurrentPhase::IDLE, cm()->has_aborted() /* force */);
464 }
465 _cm->root_regions()->cancel_scan();
466 }
467
468 void ConcurrentMarkThread::stop_service() {
469 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
470 CGC_lock->notify_all();
471 }
472
473 void ConcurrentMarkThread::sleepBeforeNextCycle() {
474 // We join here because we don't want to do the "shouldConcurrentMark()"
475 // below while the world is otherwise stopped.
476 assert(!in_progress(), "should have been cleared");
477
478 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
479 while (!started() && !should_terminate()) {
480 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
481 }
482
483 if (started()) {
484 set_in_progress();
485 }
486 }