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,
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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
49STATIC_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
67class G1ConcurrentPhase : public AllStatic {
68public:
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
77G1ConcurrentMarkThread::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
90class CMRemark : public VoidClosure {
91 G1ConcurrentMark* _cm;
92public:
93 CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
94
95 void do_void(){
96 _cm->remark();
97 }
98};
99
100class CMCleanup : public VoidClosure {
101 G1ConcurrentMark* _cm;
102public:
103 CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
104
105 void do_void(){
106 _cm->cleanup();
107 }
108};
109
110double 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
129void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
130 if (g1_policy->use_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
138class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
139 G1ConcurrentMark* _cm;
140
141 public:
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
149 ~G1ConcPhaseTimer() {
150 _cm->gc_timer_cm()->register_gc_concurrent_end();
151 }
152};
153
154static 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.
161STATIC_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.
165static 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.
176static 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
192class G1ConcPhaseManager : public StackObj {
193 G1ConcurrentMark* _cm;
194 ConcurrentGCPhaseManager _manager;
195
196public:
197 G1ConcPhaseManager(int phase, G1ConcurrentMarkThread* thread) :
198 _cm(thread->cm()),
199 _manager(phase, thread->phase_manager_stack())
200 { }
201
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
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.
216class G1ConcPhase : public StackObj {
217 G1ConcPhaseTimer _timer;
218 G1ConcPhaseManager _manager;
219
220public:
221 G1ConcPhase(int phase, G1ConcurrentMarkThread* thread) :
222 _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
223 _manager(phase, thread)
224 { }
225};
226
227bool G1ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
228 int phase = lookup_concurrent_phase(phase_name);
229 if (phase < 0) return false;
230
231 while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
232 phase_manager_stack())) {
233 assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
234 if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
235 // If idle and the goal is !idle, start a collection.
236 G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
237 }
238 }
239 return true;
240}
241
242void G1ConcurrentMarkThread::run_service() {
243 _vtime_start = os::elapsedVTime();
244
245 G1CollectedHeap* g1h = G1CollectedHeap::heap();
246 G1Policy* policy = g1h->policy();
247
248 G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
249
250 while (!should_terminate()) {
251 // wait until started is set.
252 sleep_before_next_cycle();
253 if (should_terminate()) {
254 break;
255 }
256
257 cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
258
259 GCIdMark gc_id_mark;
260
261 _cm->concurrent_cycle_start();
262
263 GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
264 {
265 ResourceMark rm;
266 HandleMark hm;
267 double cycle_start = os::elapsedVTime();
268
269 {
270 G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
271 ClassLoaderDataGraph::clear_claimed_marks();
272 }
273
274 // We have to ensure that we finish scanning the root regions
275 // before the next GC takes place. To ensure this we have to
276 // make sure that we do not join the STS until the root regions
277 // have been scanned. If we did then it's possible that a
278 // subsequent GC could block us from joining the STS and proceed
279 // without the root regions have been scanned which would be a
280 // correctness issue.
281
282 {
283 G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
284 _cm->scan_root_regions();
285 }
286
287 // It would be nice to use the G1ConcPhase class here but
288 // the "end" logging is inside the loop and not at the end of
289 // a scope. Also, the timer doesn't support nesting.
290 // Mimicking the same log output instead.
291 {
292 G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
293 jlong mark_start = os::elapsed_counter();
294 const char* cm_title = lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
295 log_info(gc, marking)("%s (%.3fs)",
296 cm_title,
297 TimeHelper::counter_to_seconds(mark_start));
298 for (uint iter = 1; !_cm->has_aborted(); ++iter) {
299 // Concurrent marking.
300 {
301 G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
302 _cm->mark_from_roots();
303 }
304 if (_cm->has_aborted()) {
305 break;
306 }
307
308 if (G1UseReferencePrecleaning) {
309 G1ConcPhase p(G1ConcurrentPhase::PRECLEAN, this);
310 _cm->preclean();
311 }
312
313 // Provide a control point before remark.
314 {
315 G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
316 }
317 if (_cm->has_aborted()) {
318 break;
319 }
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(policy, true /* remark */);
326 if (_cm->has_aborted()) {
327 break;
328 }
329
330 // Pause Remark.
331 log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
332 cm_title,
333 TimeHelper::counter_to_seconds(mark_start),
334 TimeHelper::counter_to_seconds(mark_end),
335 TimeHelper::counter_to_millis(mark_end - mark_start));
336 mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
337 CMRemark cl(_cm);
338 VM_G1Concurrent op(&cl, "Pause Remark");
339 VMThread::execute(&op);
340 if (_cm->has_aborted()) {
341 break;
342 } else if (!_cm->restart_for_overflow()) {
343 break; // Exit loop if no restart requested.
344 } else {
345 // Loop to restart for overflow.
346 mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
347 log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
348 cm_title, iter);
349 }
350 }
351 }
352
353 if (!_cm->has_aborted()) {
354 G1ConcPhase p(G1ConcurrentPhase::REBUILD_REMEMBERED_SETS, this);
355 _cm->rebuild_rem_set_concurrently();
356 }
357
358 double end_time = os::elapsedVTime();
359 // Update the total virtual time before doing this, since it will try
360 // to measure it to get the vtime for this marking.
361 _vtime_accum = (end_time - _vtime_start);
362
363 if (!_cm->has_aborted()) {
364 delay_to_keep_mmu(policy, false /* cleanup */);
365 }
366
367 if (!_cm->has_aborted()) {
368 CMCleanup cl_cl(_cm);
369 VM_G1Concurrent op(&cl_cl, "Pause Cleanup");
370 VMThread::execute(&op);
371 }
372
373 // We now want to allow clearing of the marking bitmap to be
374 // suspended by a collection pause.
375 // We may have aborted just before the remark. Do not bother clearing the
376 // bitmap then, as it has been done during mark abort.
377 if (!_cm->has_aborted()) {
378 G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
379 _cm->cleanup_for_next_mark();
380 }
381 }
382
383 // Update the number of full collections that have been
384 // completed. This will also notify the FullGCCount_lock in case a
385 // Java thread is waiting for a full GC to happen (e.g., it
386 // called System.gc() with +ExplicitGCInvokesConcurrent).
387 {
388 SuspendibleThreadSetJoiner sts_join;
389 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
390
391 _cm->concurrent_cycle_end();
392 }
393
394 cpmanager.set_phase(G1ConcurrentPhase::IDLE, _cm->has_aborted() /* force */);
395 }
396 _cm->root_regions()->cancel_scan();
397}
398
399void G1ConcurrentMarkThread::stop_service() {
400 MutexLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
401 CGC_lock->notify_all();
402}
403
404
405void G1ConcurrentMarkThread::sleep_before_next_cycle() {
406 // We join here because we don't want to do the "shouldConcurrentMark()"
407 // below while the world is otherwise stopped.
408 assert(!in_progress(), "should have been cleared");
409
410 MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
411 while (!started() && !should_terminate()) {
412 ml.wait();
413 }
414
415 if (started()) {
416 set_in_progress();
417 }
418}
419