1 /*
2 * Copyright (c) 2001, 2017, 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/suspendibleThreadSet.hpp"
34 #include "gc/g1/vm_operations_g1.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 "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->checkpointRootsFinal(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 // Marking pauses can be scheduled flexibly, so we might delay marking to meet MMU.
115 void ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
116 const G1Analytics* analytics = g1_policy->analytics();
117 if (g1_policy->adaptive_young_list_length()) {
118 double now = os::elapsedTime();
119 double prediction_ms = remark ? analytics->predict_remark_time_ms()
120 : analytics->predict_cleanup_time_ms();
121 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
122 jlong sleep_time_ms = mmu_tracker->when_ms(now, prediction_ms);
123 os::sleep(this, sleep_time_ms, false);
124 }
125 }
126
127 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
128 G1ConcurrentMark* _cm;
129
130 public:
131 G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
132 GCTraceConcTimeImpl<LogLevel::Info, LogTag::_gc, LogTag::_marking>(title),
133 _cm(cm)
134 {
135 _cm->gc_timer_cm()->register_gc_concurrent_start(title);
136 }
137
138 ~G1ConcPhaseTimer() {
139 _cm->gc_timer_cm()->register_gc_concurrent_end();
140 }
141 };
142
143 static const char* const concurrent_phase_names[] = {
144 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
145 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
146 #undef CONCURRENT_PHASE_NAME
147 NULL // terminator
148 };
149 // Verify dense enum assumption. +1 for terminator.
150 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
151 ARRAY_SIZE(concurrent_phase_names));
152
153 // Returns the phase number for name, or a negative value if unknown.
154 static int lookup_concurrent_phase(const char* name) {
155 const char* const* names = concurrent_phase_names;
156 for (uint i = 0; names[i] != NULL; ++i) {
157 if (strcmp(name, names[i]) == 0) {
158 return static_cast<int>(i);
159 }
160 }
161 return -1;
162 }
163
164 // The phase must be valid and must have a title.
165 static const char* lookup_concurrent_phase_title(int phase) {
166 static const char* const titles[] = {
167 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
168 EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
169 #undef CONCURRENT_PHASE_TITLE
170 };
171 // Verify dense enum assumption.
172 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
173
174 assert(0 <= phase, "precondition");
175 assert((uint)phase < ARRAY_SIZE(titles), "precondition");
176 const char* title = titles[phase];
177 assert(title != NULL, "precondition");
178 return title;
179 }
180
181 class G1ConcPhaseManager : public StackObj {
182 G1ConcurrentMark* _cm;
183 ConcurrentGCPhaseManager _manager;
184
185 public:
186 G1ConcPhaseManager(int phase, ConcurrentMarkThread* thread) :
187 _cm(thread->cm()),
188 _manager(phase, thread->phase_manager_stack())
189 { }
190
191 ~G1ConcPhaseManager() {
192 // Deactivate the manager if marking aborted, to avoid blocking on
193 // phase exit when the phase has been requested.
194 if (_cm->has_aborted()) {
195 _manager.deactivate();
196 }
197 }
198
199 void set_phase(int phase, bool force) {
200 _manager.set_phase(phase, force);
201 }
202 };
203
204 // Combine phase management and timing into one convenient utility.
205 class G1ConcPhase : public StackObj {
206 G1ConcPhaseTimer _timer;
207 G1ConcPhaseManager _manager;
208
209 public:
210 G1ConcPhase(int phase, ConcurrentMarkThread* thread) :
211 _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
212 _manager(phase, thread)
213 { }
214 };
215
216 const char* const* ConcurrentMarkThread::concurrent_phases() const {
217 return concurrent_phase_names;
218 }
219
220 bool ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
221 int phase = lookup_concurrent_phase(phase_name);
222 if (phase < 0) return false;
223
224 while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
225 phase_manager_stack())) {
226 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
227 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
228 // If idle and the goal is !idle, start a collection.
229 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
230 }
231 }
232 return true;
233 }
234
235 void ConcurrentMarkThread::run_service() {
236 _vtime_start = os::elapsedVTime();
237
238 G1CollectedHeap* g1h = G1CollectedHeap::heap();
239 G1Policy* g1_policy = g1h->g1_policy();
240
241 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
242
243 while (!should_terminate()) {
244 // wait until started is set.
245 sleepBeforeNextCycle();
246 if (should_terminate()) {
247 break;
248 }
249
250 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
251
252 GCIdMark gc_id_mark;
253
254 cm()->concurrent_cycle_start();
255
256 assert(GCId::current() != GCId::undefined(), "GC id should have been set up by the initial mark GC.");
257
258 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
259 {
260 ResourceMark rm;
261 HandleMark hm;
262 double cycle_start = os::elapsedVTime();
263
264 {
265 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
266 ClassLoaderDataGraph::clear_claimed_marks();
267 }
268
269 // We have to ensure that we finish scanning the root regions
270 // before the next GC takes place. To ensure this we have to
271 // make sure that we do not join the STS until the root regions
272 // have been scanned. If we did then it's possible that a
273 // subsequent GC could block us from joining the STS and proceed
274 // without the root regions have been scanned which would be a
275 // correctness issue.
276
277 {
278 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
279 _cm->scan_root_regions();
280 }
281
282 // It would be nice to use the G1ConcPhase class here but
283 // the "end" logging is inside the loop and not at the end of
284 // a scope. Also, the timer doesn't support nesting.
285 // Mimicking the same log output instead.
286 {
287 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
288 jlong mark_start = os::elapsed_counter();
289 const char* cm_title =
290 lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
291 log_info(gc, marking)("%s (%.3fs)",
292 cm_title,
293 TimeHelper::counter_to_seconds(mark_start));
294 for (uint iter = 1; !cm()->has_aborted(); ++iter) {
295 // Concurrent marking.
296 {
297 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
298 _cm->mark_from_roots();
299 }
300 if (cm()->has_aborted()) break;
301
302 // Provide a control point after mark_from_roots.
303 {
304 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
305 }
306 if (cm()->has_aborted()) break;
307
308 // Delay remark pause for MMU.
309 double mark_end_time = os::elapsedVTime();
310 jlong mark_end = os::elapsed_counter();
311 _vtime_mark_accum += (mark_end_time - cycle_start);
312 delay_to_keep_mmu(g1_policy, true /* remark */);
313 if (cm()->has_aborted()) break;
314
315 // Pause Remark.
316 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
317 cm_title,
318 TimeHelper::counter_to_seconds(mark_start),
319 TimeHelper::counter_to_seconds(mark_end),
320 TimeHelper::counter_to_millis(mark_end - mark_start));
321 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
322 CMCheckpointRootsFinalClosure final_cl(_cm);
323 VM_CGC_Operation op(&final_cl, "Pause Remark");
324 VMThread::execute(&op);
325 if (cm()->has_aborted()) {
326 break;
327 } else if (!cm()->restart_for_overflow()) {
328 break; // Exit loop if no restart requested.
329 } else {
330 // Loop to restart for overflow.
331 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
332 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
333 cm_title, iter);
334 }
335 }
336 }
337
338 if (!cm()->has_aborted()) {
339 G1ConcPhase p(G1ConcurrentPhase::CREATE_LIVE_DATA, this);
340 cm()->create_live_data();
341 }
342
343 double end_time = os::elapsedVTime();
344 // Update the total virtual time before doing this, since it will try
345 // to measure it to get the vtime for this marking. We purposely
346 // neglect the presumably-short "completeCleanup" phase here.
347 _vtime_accum = (end_time - _vtime_start);
348
349 if (!cm()->has_aborted()) {
350 delay_to_keep_mmu(g1_policy, false /* cleanup */);
351
352 CMCleanUp cl_cl(_cm);
353 VM_CGC_Operation op(&cl_cl, "Pause Cleanup");
354 VMThread::execute(&op);
355 } else {
356 // We don't want to update the marking status if a GC pause
357 // is already underway.
358 SuspendibleThreadSetJoiner sts_join;
359 g1h->collector_state()->set_mark_in_progress(false);
360 }
361
362 // Check if cleanup set the free_regions_coming flag. If it
363 // hasn't, we can just skip the next step.
364 if (g1h->free_regions_coming()) {
365 // The following will finish freeing up any regions that we
366 // found to be empty during cleanup. We'll do this part
367 // without joining the suspendible set. If an evacuation pause
368 // takes place, then we would carry on freeing regions in
369 // case they are needed by the pause. If a Full GC takes
370 // place, it would wait for us to process the regions
371 // reclaimed by cleanup.
372
373 // Now do the concurrent cleanup operation.
374 G1ConcPhase p(G1ConcurrentPhase::COMPLETE_CLEANUP, this);
375 _cm->complete_cleanup();
376
377 // Notify anyone who's waiting that there are no more free
378 // regions coming. We have to do this before we join the STS
379 // (in fact, we should not attempt to join the STS in the
380 // interval between finishing the cleanup pause and clearing
381 // the free_regions_coming flag) otherwise we might deadlock:
382 // a GC worker could be blocked waiting for the notification
383 // whereas this thread will be blocked for the pause to finish
384 // while it's trying to join the STS, which is conditional on
385 // the GC workers finishing.
386 g1h->reset_free_regions_coming();
387 }
388 guarantee(cm()->cleanup_list_is_empty(),
389 "at this point there should be no regions on the cleanup list");
390
391 // There is a tricky race before recording that the concurrent
392 // cleanup has completed and a potential Full GC starting around
393 // the same time. We want to make sure that the Full GC calls
394 // abort() on concurrent mark after
395 // record_concurrent_mark_cleanup_completed(), since abort() is
396 // the method that will reset the concurrent mark state. If we
397 // end up calling record_concurrent_mark_cleanup_completed()
398 // after abort() then we might incorrectly undo some of the work
399 // abort() did. Checking the has_aborted() flag after joining
400 // the STS allows the correct ordering of the two methods. There
401 // are two scenarios:
402 //
403 // a) If we reach here before the Full GC, the fact that we have
404 // joined the STS means that the Full GC cannot start until we
405 // leave the STS, so record_concurrent_mark_cleanup_completed()
406 // will complete before abort() is called.
407 //
408 // b) If we reach here during the Full GC, we'll be held up from
409 // joining the STS until the Full GC is done, which means that
410 // abort() will have completed and has_aborted() will return
411 // true to prevent us from calling
412 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
413 // not needed any more as the concurrent mark state has been
414 // already reset).
415 {
416 SuspendibleThreadSetJoiner sts_join;
417 if (!cm()->has_aborted()) {
418 g1_policy->record_concurrent_mark_cleanup_completed();
419 } else {
420 log_info(gc, marking)("Concurrent Mark Abort");
421 }
422 }
423
424 // We now want to allow clearing of the marking bitmap to be
425 // suspended by a collection pause.
426 // We may have aborted just before the remark. Do not bother clearing the
427 // bitmap then, as it has been done during mark abort.
428 if (!cm()->has_aborted()) {
429 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
430 _cm->cleanup_for_next_mark();
431 } else {
432 assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear");
433 }
434 }
435
436 // Update the number of full collections that have been
437 // completed. This will also notify the FullGCCount_lock in case a
438 // Java thread is waiting for a full GC to happen (e.g., it
439 // called System.gc() with +ExplicitGCInvokesConcurrent).
440 {
441 SuspendibleThreadSetJoiner sts_join;
442 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
443
444 cm()->concurrent_cycle_end();
445 }
446
447 cpmanager.set_phase(G1ConcurrentPhase::IDLE, cm()->has_aborted() /* force */);
448 }
449 _cm->root_regions()->cancel_scan();
450 }
451
452 void ConcurrentMarkThread::stop_service() {
453 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
454 CGC_lock->notify_all();
455 }
456
457 void ConcurrentMarkThread::sleepBeforeNextCycle() {
458 // We join here because we don't want to do the "shouldConcurrentMark()"
459 // below while the world is otherwise stopped.
460 assert(!in_progress(), "should have been cleared");
461
462 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
463 while (!started() && !should_terminate()) {
464 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
465 }
466
467 if (started()) {
468 set_in_progress();
469 }
470 }