Thu, 19 Jun 2014 13:31:14 +0200
8043607: Add a GC id as a log decoration similar to PrintGCTimeStamps
Reviewed-by: jwilhelm, ehelin, tschatzl
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
29 #include "gc_implementation/g1/g1Log.hpp"
30 #include "gc_implementation/g1/g1MMUTracker.hpp"
31 #include "gc_implementation/g1/vm_operations_g1.hpp"
32 #include "gc_implementation/shared/gcTrace.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "runtime/vmThread.hpp"
36 // ======= Concurrent Mark Thread ========
38 // The CM thread is created when the G1 garbage collector is used
40 SurrogateLockerThread*
41 ConcurrentMarkThread::_slt = NULL;
43 ConcurrentMarkThread::ConcurrentMarkThread(ConcurrentMark* cm) :
44 ConcurrentGCThread(),
45 _cm(cm),
46 _started(false),
47 _in_progress(false),
48 _vtime_accum(0.0),
49 _vtime_mark_accum(0.0) {
50 create_and_start();
51 }
53 class CMCheckpointRootsFinalClosure: public VoidClosure {
55 ConcurrentMark* _cm;
56 public:
58 CMCheckpointRootsFinalClosure(ConcurrentMark* cm) :
59 _cm(cm) {}
61 void do_void(){
62 _cm->checkpointRootsFinal(false); // !clear_all_soft_refs
63 }
64 };
66 class CMCleanUp: public VoidClosure {
67 ConcurrentMark* _cm;
68 public:
70 CMCleanUp(ConcurrentMark* cm) :
71 _cm(cm) {}
73 void do_void(){
74 _cm->cleanup();
75 }
76 };
80 void ConcurrentMarkThread::run() {
81 initialize_in_thread();
82 _vtime_start = os::elapsedVTime();
83 wait_for_universe_init();
85 G1CollectedHeap* g1h = G1CollectedHeap::heap();
86 G1CollectorPolicy* g1_policy = g1h->g1_policy();
87 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
88 Thread *current_thread = Thread::current();
90 while (!_should_terminate) {
91 // wait until started is set.
92 sleepBeforeNextCycle();
93 if (_should_terminate) {
94 break;
95 }
97 {
98 ResourceMark rm;
99 HandleMark hm;
100 double cycle_start = os::elapsedVTime();
102 // We have to ensure that we finish scanning the root regions
103 // before the next GC takes place. To ensure this we have to
104 // make sure that we do not join the STS until the root regions
105 // have been scanned. If we did then it's possible that a
106 // subsequent GC could block us from joining the STS and proceed
107 // without the root regions have been scanned which would be a
108 // correctness issue.
110 double scan_start = os::elapsedTime();
111 if (!cm()->has_aborted()) {
112 if (G1Log::fine()) {
113 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
114 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]");
115 }
117 _cm->scanRootRegions();
119 double scan_end = os::elapsedTime();
120 if (G1Log::fine()) {
121 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
122 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf secs]",
123 scan_end - scan_start);
124 }
125 }
127 double mark_start_sec = os::elapsedTime();
128 if (G1Log::fine()) {
129 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
130 gclog_or_tty->print_cr("[GC concurrent-mark-start]");
131 }
133 int iter = 0;
134 do {
135 iter++;
136 if (!cm()->has_aborted()) {
137 _cm->markFromRoots();
138 }
140 double mark_end_time = os::elapsedVTime();
141 double mark_end_sec = os::elapsedTime();
142 _vtime_mark_accum += (mark_end_time - cycle_start);
143 if (!cm()->has_aborted()) {
144 if (g1_policy->adaptive_young_list_length()) {
145 double now = os::elapsedTime();
146 double remark_prediction_ms = g1_policy->predict_remark_time_ms();
147 jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms);
148 os::sleep(current_thread, sleep_time_ms, false);
149 }
151 if (G1Log::fine()) {
152 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
153 gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf secs]",
154 mark_end_sec - mark_start_sec);
155 }
157 CMCheckpointRootsFinalClosure final_cl(_cm);
158 VM_CGC_Operation op(&final_cl, "GC remark", true /* needs_pll */);
159 VMThread::execute(&op);
160 }
161 if (cm()->restart_for_overflow()) {
162 if (G1TraceMarkStackOverflow) {
163 gclog_or_tty->print_cr("Restarting conc marking because of MS overflow "
164 "in remark (restart #%d).", iter);
165 }
166 if (G1Log::fine()) {
167 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
168 gclog_or_tty->print_cr("[GC concurrent-mark-restart-for-overflow]");
169 }
170 }
171 } while (cm()->restart_for_overflow());
173 double end_time = os::elapsedVTime();
174 // Update the total virtual time before doing this, since it will try
175 // to measure it to get the vtime for this marking. We purposely
176 // neglect the presumably-short "completeCleanup" phase here.
177 _vtime_accum = (end_time - _vtime_start);
179 if (!cm()->has_aborted()) {
180 if (g1_policy->adaptive_young_list_length()) {
181 double now = os::elapsedTime();
182 double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms();
183 jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms);
184 os::sleep(current_thread, sleep_time_ms, false);
185 }
187 CMCleanUp cl_cl(_cm);
188 VM_CGC_Operation op(&cl_cl, "GC cleanup", false /* needs_pll */);
189 VMThread::execute(&op);
190 } else {
191 // We don't want to update the marking status if a GC pause
192 // is already underway.
193 _sts.join();
194 g1h->set_marking_complete();
195 _sts.leave();
196 }
198 // Check if cleanup set the free_regions_coming flag. If it
199 // hasn't, we can just skip the next step.
200 if (g1h->free_regions_coming()) {
201 // The following will finish freeing up any regions that we
202 // found to be empty during cleanup. We'll do this part
203 // without joining the suspendible set. If an evacuation pause
204 // takes place, then we would carry on freeing regions in
205 // case they are needed by the pause. If a Full GC takes
206 // place, it would wait for us to process the regions
207 // reclaimed by cleanup.
209 double cleanup_start_sec = os::elapsedTime();
210 if (G1Log::fine()) {
211 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
212 gclog_or_tty->print_cr("[GC concurrent-cleanup-start]");
213 }
215 // Now do the concurrent cleanup operation.
216 _cm->completeCleanup();
218 // Notify anyone who's waiting that there are no more free
219 // regions coming. We have to do this before we join the STS
220 // (in fact, we should not attempt to join the STS in the
221 // interval between finishing the cleanup pause and clearing
222 // the free_regions_coming flag) otherwise we might deadlock:
223 // a GC worker could be blocked waiting for the notification
224 // whereas this thread will be blocked for the pause to finish
225 // while it's trying to join the STS, which is conditional on
226 // the GC workers finishing.
227 g1h->reset_free_regions_coming();
229 double cleanup_end_sec = os::elapsedTime();
230 if (G1Log::fine()) {
231 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
232 gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf secs]",
233 cleanup_end_sec - cleanup_start_sec);
234 }
235 }
236 guarantee(cm()->cleanup_list_is_empty(),
237 "at this point there should be no regions on the cleanup list");
239 // There is a tricky race before recording that the concurrent
240 // cleanup has completed and a potential Full GC starting around
241 // the same time. We want to make sure that the Full GC calls
242 // abort() on concurrent mark after
243 // record_concurrent_mark_cleanup_completed(), since abort() is
244 // the method that will reset the concurrent mark state. If we
245 // end up calling record_concurrent_mark_cleanup_completed()
246 // after abort() then we might incorrectly undo some of the work
247 // abort() did. Checking the has_aborted() flag after joining
248 // the STS allows the correct ordering of the two methods. There
249 // are two scenarios:
250 //
251 // a) If we reach here before the Full GC, the fact that we have
252 // joined the STS means that the Full GC cannot start until we
253 // leave the STS, so record_concurrent_mark_cleanup_completed()
254 // will complete before abort() is called.
255 //
256 // b) If we reach here during the Full GC, we'll be held up from
257 // joining the STS until the Full GC is done, which means that
258 // abort() will have completed and has_aborted() will return
259 // true to prevent us from calling
260 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
261 // not needed any more as the concurrent mark state has been
262 // already reset).
263 _sts.join();
264 if (!cm()->has_aborted()) {
265 g1_policy->record_concurrent_mark_cleanup_completed();
266 }
267 _sts.leave();
269 if (cm()->has_aborted()) {
270 if (G1Log::fine()) {
271 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
272 gclog_or_tty->print_cr("[GC concurrent-mark-abort]");
273 }
274 }
276 // We now want to allow clearing of the marking bitmap to be
277 // suspended by a collection pause.
278 _sts.join();
279 _cm->clearNextBitmap();
280 _sts.leave();
281 }
283 // Update the number of full collections that have been
284 // completed. This will also notify the FullGCCount_lock in case a
285 // Java thread is waiting for a full GC to happen (e.g., it
286 // called System.gc() with +ExplicitGCInvokesConcurrent).
287 _sts.join();
288 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
289 g1h->register_concurrent_cycle_end();
290 _sts.leave();
291 }
292 assert(_should_terminate, "just checking");
294 terminate();
295 }
298 void ConcurrentMarkThread::yield() {
299 _sts.yield("Concurrent Mark");
300 }
302 void ConcurrentMarkThread::stop() {
303 {
304 MutexLockerEx ml(Terminator_lock);
305 _should_terminate = true;
306 }
308 {
309 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
310 CGC_lock->notify_all();
311 }
313 {
314 MutexLockerEx ml(Terminator_lock);
315 while (!_has_terminated) {
316 Terminator_lock->wait();
317 }
318 }
319 }
321 void ConcurrentMarkThread::print() const {
322 print_on(tty);
323 }
325 void ConcurrentMarkThread::print_on(outputStream* st) const {
326 st->print("\"G1 Main Concurrent Mark GC Thread\" ");
327 Thread::print_on(st);
328 st->cr();
329 }
331 void ConcurrentMarkThread::sleepBeforeNextCycle() {
332 // We join here because we don't want to do the "shouldConcurrentMark()"
333 // below while the world is otherwise stopped.
334 assert(!in_progress(), "should have been cleared");
336 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
337 while (!started() && !_should_terminate) {
338 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
339 }
341 if (started()) {
342 set_in_progress();
343 clear_started();
344 }
345 }
347 // Note: As is the case with CMS - this method, although exported
348 // by the ConcurrentMarkThread, which is a non-JavaThread, can only
349 // be called by a JavaThread. Currently this is done at vm creation
350 // time (post-vm-init) by the main/Primordial (Java)Thread.
351 // XXX Consider changing this in the future to allow the CM thread
352 // itself to create this thread?
353 void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) {
354 assert(UseG1GC, "SLT thread needed only for concurrent GC");
355 assert(THREAD->is_Java_thread(), "must be a Java thread");
356 assert(_slt == NULL, "SLT already created");
357 _slt = SurrogateLockerThread::make(THREAD);
358 }