1 /*
2 * Copyright (c) 2001, 2015, 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 "gc/g1/concurrentMarkThread.inline.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1CollectorPolicy.hpp"
29 #include "gc/shared/gcId.hpp"
30 #include "gc/g1/g1Log.hpp"
31 #include "gc/g1/vm_operations_g1.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTraceTime.hpp"
34 #include "gc/shared/isGCActiveMark.hpp"
35 #include "runtime/interfaceSupport.hpp"
36
37 VM_G1CollectForAllocation::VM_G1CollectForAllocation(uint gc_count_before,
38 size_t word_size)
39 : VM_G1OperationWithAllocRequest(gc_count_before, word_size,
40 GCCause::_allocation_failure) {
41 guarantee(word_size != 0, "An allocation should always be requested with this operation.");
42 }
43
44 void VM_G1CollectForAllocation::doit() {
45 G1CollectedHeap* g1h = G1CollectedHeap::heap();
46 GCCauseSetter x(g1h, _gc_cause);
47
48 _result = g1h->satisfy_failed_allocation(_word_size, allocation_context(), &_pause_succeeded);
49 assert(_result == NULL || _pause_succeeded,
50 "if we get back a result, the pause should have succeeded");
51 }
52
53 void VM_G1CollectFull::doit() {
54 G1CollectedHeap* g1h = G1CollectedHeap::heap();
55 GCCauseSetter x(g1h, _gc_cause);
56 g1h->do_full_collection(false /* clear_all_soft_refs */);
57 }
58
59 VM_G1IncCollectionPause::VM_G1IncCollectionPause(uint gc_count_before,
60 size_t word_size,
61 bool should_initiate_conc_mark,
62 double target_pause_time_ms,
63 GCCause::Cause gc_cause)
64 : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),
65 _should_initiate_conc_mark(should_initiate_conc_mark),
66 _target_pause_time_ms(target_pause_time_ms),
67 _should_retry_gc(false),
68 _old_marking_cycles_completed_before(0) {
69 guarantee(target_pause_time_ms > 0.0,
70 "target_pause_time_ms = %1.6lf should be positive",
71 target_pause_time_ms);
72 _gc_cause = gc_cause;
73 }
74
75 bool VM_G1IncCollectionPause::doit_prologue() {
76 bool res = VM_G1OperationWithAllocRequest::doit_prologue();
77 if (!res) {
78 if (_should_initiate_conc_mark) {
79 // The prologue can fail for a couple of reasons. The first is that another GC
80 // got scheduled and prevented the scheduling of the initial mark GC. The
81 // second is that the GC locker may be active and the heap can't be expanded.
82 // In both cases we want to retry the GC so that the initial mark pause is
83 // actually scheduled. In the second case, however, we should stall until
84 // until the GC locker is no longer active and then retry the initial mark GC.
85 _should_retry_gc = true;
86 }
87 }
88 return res;
89 }
90
91 void VM_G1IncCollectionPause::doit() {
92 G1CollectedHeap* g1h = G1CollectedHeap::heap();
93 assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause),
94 "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle");
95
96 if (_word_size > 0) {
97 // An allocation has been requested. So, try to do that first.
98 _result = g1h->attempt_allocation_at_safepoint(_word_size,
99 allocation_context(),
100 false /* expect_null_cur_alloc_region */);
101 if (_result != NULL) {
102 // If we can successfully allocate before we actually do the
103 // pause then we will consider this pause successful.
104 _pause_succeeded = true;
105 return;
106 }
107 }
108
109 GCCauseSetter x(g1h, _gc_cause);
110 if (_should_initiate_conc_mark) {
111 // It's safer to read old_marking_cycles_completed() here, given
112 // that noone else will be updating it concurrently. Since we'll
113 // only need it if we're initiating a marking cycle, no point in
114 // setting it earlier.
115 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
116
117 // At this point we are supposed to start a concurrent cycle. We
118 // will do so if one is not already in progress.
119 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
120
121 // The above routine returns true if we were able to force the
122 // next GC pause to be an initial mark; it returns false if a
123 // marking cycle is already in progress.
124 //
125 // If a marking cycle is already in progress just return and skip the
126 // pause below - if the reason for requesting this initial mark pause
127 // was due to a System.gc() then the requesting thread should block in
128 // doit_epilogue() until the marking cycle is complete.
129 //
130 // If this initial mark pause was requested as part of a humongous
131 // allocation then we know that the marking cycle must just have
132 // been started by another thread (possibly also allocating a humongous
133 // object) as there was no active marking cycle when the requesting
134 // thread checked before calling collect() in
135 // attempt_allocation_humongous(). Retrying the GC, in this case,
136 // will cause the requesting thread to spin inside collect() until the
137 // just started marking cycle is complete - which may be a while. So
138 // we do NOT retry the GC.
139 if (!res) {
140 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
141 if (_gc_cause != GCCause::_g1_humongous_allocation) {
142 _should_retry_gc = true;
143 }
144 return;
145 }
146 }
147
148 _pause_succeeded =
149 g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
150 if (_pause_succeeded && _word_size > 0) {
151 // An allocation had been requested.
152 _result = g1h->attempt_allocation_at_safepoint(_word_size,
153 allocation_context(),
154 true /* expect_null_cur_alloc_region */);
155 } else {
156 assert(_result == NULL, "invariant");
157 if (!_pause_succeeded) {
158 // Another possible reason reason for the pause to not be successful
159 // is that, again, the GC locker is active (and has become active
160 // since the prologue was executed). In this case we should retry
161 // the pause after waiting for the GC locker to become inactive.
162 _should_retry_gc = true;
163 }
164 }
165 }
166
167 void VM_G1IncCollectionPause::doit_epilogue() {
168 VM_G1OperationWithAllocRequest::doit_epilogue();
169
170 // If the pause was initiated by a System.gc() and
171 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
172 // that just started (or maybe one that was already in progress) to
173 // finish.
174 if (GCCause::is_user_requested_gc(_gc_cause) &&
175 _should_initiate_conc_mark) {
176 assert(ExplicitGCInvokesConcurrent,
177 "the only way to be here is if ExplicitGCInvokesConcurrent is set");
178
179 G1CollectedHeap* g1h = G1CollectedHeap::heap();
180
181 // In the doit() method we saved g1h->old_marking_cycles_completed()
182 // in the _old_marking_cycles_completed_before field. We have to
183 // wait until we observe that g1h->old_marking_cycles_completed()
184 // has increased by at least one. This can happen if a) we started
185 // a cycle and it completes, b) a cycle already in progress
186 // completes, or c) a Full GC happens.
187
188 // If the condition has already been reached, there's no point in
189 // actually taking the lock and doing the wait.
190 if (g1h->old_marking_cycles_completed() <=
191 _old_marking_cycles_completed_before) {
192 // The following is largely copied from CMS
193
194 Thread* thr = Thread::current();
195 assert(thr->is_Java_thread(), "invariant");
196 JavaThread* jt = (JavaThread*)thr;
197 ThreadToNativeFromVM native(jt);
198
199 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
200 while (g1h->old_marking_cycles_completed() <=
201 _old_marking_cycles_completed_before) {
202 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
203 }
204 }
205 }
206 }
207
208 void VM_CGC_Operation::acquire_pending_list_lock() {
209 assert(_needs_pll, "don't call this otherwise");
210 // The caller may block while communicating
211 // with the SLT thread in order to acquire/release the PLL.
212 SurrogateLockerThread* slt = ConcurrentMarkThread::slt();
213 if (slt != NULL) {
214 slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
215 } else {
216 SurrogateLockerThread::report_missing_slt();
217 }
218 }
219
220 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
221 assert(_needs_pll, "don't call this otherwise");
222 // The caller may block while communicating
223 // with the SLT thread in order to acquire/release the PLL.
224 ConcurrentMarkThread::slt()->
225 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
226 }
227
228 void VM_CGC_Operation::doit() {
229 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
230 G1CollectedHeap* g1h = G1CollectedHeap::heap();
231 GCIdMark gc_id_mark(_gc_id);
232 GCTraceTime t(_printGCMessage, G1Log::fine(), true, g1h->gc_timer_cm());
233 IsGCActiveMark x;
234 _cl->do_void();
235 }
236
237 bool VM_CGC_Operation::doit_prologue() {
238 // Note the relative order of the locks must match that in
239 // VM_GC_Operation::doit_prologue() or deadlocks can occur
240 if (_needs_pll) {
241 acquire_pending_list_lock();
242 }
243
244 Heap_lock->lock();
245 return true;
246 }
247
248 void VM_CGC_Operation::doit_epilogue() {
249 // Note the relative order of the unlocks must match that in
250 // VM_GC_Operation::doit_epilogue()
251 Heap_lock->unlock();
252 if (_needs_pll) {
253 release_and_notify_pending_list_lock();
254 }
255 }