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