Thu, 07 Aug 2014 22:28:53 +0200
8054341: Remove some obsolete code in G1CollectedHeap class
Summary: Remove dead code.
Reviewed-by: stefank, brutisso
1 /*
2 * Copyright (c) 2001, 2013, 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 */
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 SuspendibleThreadSetJoiner sts;
194 g1h->set_marking_complete();
195 }
197 // Check if cleanup set the free_regions_coming flag. If it
198 // hasn't, we can just skip the next step.
199 if (g1h->free_regions_coming()) {
200 // The following will finish freeing up any regions that we
201 // found to be empty during cleanup. We'll do this part
202 // without joining the suspendible set. If an evacuation pause
203 // takes place, then we would carry on freeing regions in
204 // case they are needed by the pause. If a Full GC takes
205 // place, it would wait for us to process the regions
206 // reclaimed by cleanup.
208 double cleanup_start_sec = os::elapsedTime();
209 if (G1Log::fine()) {
210 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
211 gclog_or_tty->print_cr("[GC concurrent-cleanup-start]");
212 }
214 // Now do the concurrent cleanup operation.
215 _cm->completeCleanup();
217 // Notify anyone who's waiting that there are no more free
218 // regions coming. We have to do this before we join the STS
219 // (in fact, we should not attempt to join the STS in the
220 // interval between finishing the cleanup pause and clearing
221 // the free_regions_coming flag) otherwise we might deadlock:
222 // a GC worker could be blocked waiting for the notification
223 // whereas this thread will be blocked for the pause to finish
224 // while it's trying to join the STS, which is conditional on
225 // the GC workers finishing.
226 g1h->reset_free_regions_coming();
228 double cleanup_end_sec = os::elapsedTime();
229 if (G1Log::fine()) {
230 gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id());
231 gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf secs]",
232 cleanup_end_sec - cleanup_start_sec);
233 }
234 }
235 guarantee(cm()->cleanup_list_is_empty(),
236 "at this point there should be no regions on the cleanup list");
238 // There is a tricky race before recording that the concurrent
239 // cleanup has completed and a potential Full GC starting around
240 // the same time. We want to make sure that the Full GC calls
241 // abort() on concurrent mark after
242 // record_concurrent_mark_cleanup_completed(), since abort() is
243 // the method that will reset the concurrent mark state. If we
244 // end up calling record_concurrent_mark_cleanup_completed()
245 // after abort() then we might incorrectly undo some of the work
246 // abort() did. Checking the has_aborted() flag after joining
247 // the STS allows the correct ordering of the two methods. There
248 // are two scenarios:
249 //
250 // a) If we reach here before the Full GC, the fact that we have
251 // joined the STS means that the Full GC cannot start until we
252 // leave the STS, so record_concurrent_mark_cleanup_completed()
253 // will complete before abort() is called.
254 //
255 // b) If we reach here during the Full GC, we'll be held up from
256 // joining the STS until the Full GC is done, which means that
257 // abort() will have completed and has_aborted() will return
258 // true to prevent us from calling
259 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
260 // not needed any more as the concurrent mark state has been
261 // already reset).
262 {
263 SuspendibleThreadSetJoiner sts;
264 if (!cm()->has_aborted()) {
265 g1_policy->record_concurrent_mark_cleanup_completed();
266 }
267 }
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 // We may have aborted just before the remark. Do not bother clearing the
279 // bitmap then, as it has been done during mark abort.
280 if (!cm()->has_aborted()) {
281 SuspendibleThreadSetJoiner sts;
282 _cm->clearNextBitmap();
283 } else {
284 assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear");
285 }
286 }
288 // Update the number of full collections that have been
289 // completed. This will also notify the FullGCCount_lock in case a
290 // Java thread is waiting for a full GC to happen (e.g., it
291 // called System.gc() with +ExplicitGCInvokesConcurrent).
292 {
293 SuspendibleThreadSetJoiner sts;
294 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
295 g1h->register_concurrent_cycle_end();
296 }
297 }
298 assert(_should_terminate, "just checking");
300 terminate();
301 }
303 void ConcurrentMarkThread::stop() {
304 {
305 MutexLockerEx ml(Terminator_lock);
306 _should_terminate = true;
307 }
309 {
310 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
311 CGC_lock->notify_all();
312 }
314 {
315 MutexLockerEx ml(Terminator_lock);
316 while (!_has_terminated) {
317 Terminator_lock->wait();
318 }
319 }
320 }
322 void ConcurrentMarkThread::print() const {
323 print_on(tty);
324 }
326 void ConcurrentMarkThread::print_on(outputStream* st) const {
327 st->print("\"G1 Main Concurrent Mark GC Thread\" ");
328 Thread::print_on(st);
329 st->cr();
330 }
332 void ConcurrentMarkThread::sleepBeforeNextCycle() {
333 // We join here because we don't want to do the "shouldConcurrentMark()"
334 // below while the world is otherwise stopped.
335 assert(!in_progress(), "should have been cleared");
337 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
338 while (!started() && !_should_terminate) {
339 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
340 }
342 if (started()) {
343 set_in_progress();
344 clear_started();
345 }
346 }
348 // Note: As is the case with CMS - this method, although exported
349 // by the ConcurrentMarkThread, which is a non-JavaThread, can only
350 // be called by a JavaThread. Currently this is done at vm creation
351 // time (post-vm-init) by the main/Primordial (Java)Thread.
352 // XXX Consider changing this in the future to allow the CM thread
353 // itself to create this thread?
354 void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) {
355 assert(UseG1GC, "SLT thread needed only for concurrent GC");
356 assert(THREAD->is_Java_thread(), "must be a Java thread");
357 assert(_slt == NULL, "SLT already created");
358 _slt = SurrogateLockerThread::make(THREAD);
359 }