1 /*
2 * Copyright (c) 2001, 2012, 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_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/vm_operations_g1.hpp"
31 #include "gc_implementation/shared/isGCActiveMark.hpp"
32 #include "gc_implementation/g1/vm_operations_g1.hpp"
33 #include "runtime/interfaceSupport.hpp"
34
35 VM_G1CollectForAllocation::VM_G1CollectForAllocation(
36 unsigned int gc_count_before,
37 size_t word_size)
38 : VM_G1OperationWithAllocRequest(gc_count_before, word_size,
39 GCCause::_allocation_failure) {
40 guarantee(word_size > 0, "an allocation should always be requested");
41 }
42
43 void VM_G1CollectForAllocation::doit() {
44 G1CollectedHeap* g1h = G1CollectedHeap::heap();
45 GCCauseSetter x(g1h, _gc_cause);
46 _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded);
47 assert(_result == NULL || _pause_succeeded,
48 "if we get back a result, the pause should have succeeded");
49 }
50
51 void VM_G1CollectFull::doit() {
52 G1CollectedHeap* g1h = G1CollectedHeap::heap();
53 GCCauseSetter x(g1h, _gc_cause);
54 g1h->do_full_collection(false /* clear_all_soft_refs */);
55 }
56
57 VM_G1IncCollectionPause::VM_G1IncCollectionPause(
58 unsigned int gc_count_before,
59 size_t word_size,
60 bool should_initiate_conc_mark,
61 double target_pause_time_ms,
62 GCCause::Cause gc_cause)
63 : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),
64 _should_initiate_conc_mark(should_initiate_conc_mark),
65 _target_pause_time_ms(target_pause_time_ms),
66 _should_retry_gc(false),
67 _old_marking_cycles_completed_before(0) {
68 guarantee(target_pause_time_ms > 0.0,
69 err_msg("target_pause_time_ms = %1.6lf should be positive",
70 target_pause_time_ms));
71 guarantee(word_size == 0 || gc_cause == GCCause::_g1_inc_collection_pause,
72 "we can only request an allocation if the GC cause is for "
73 "an incremental GC pause");
74 _gc_cause = gc_cause;
75 }
76
77 bool VM_G1IncCollectionPause::doit_prologue() {
78 bool res = VM_GC_Operation::doit_prologue();
79 if (!res) {
80 if (_should_initiate_conc_mark) {
81 // The prologue can fail for a couple of reasons. The first is that another GC
82 // got scheduled and prevented the scheduling of the initial mark GC. The
83 // second is that the GC locker may be active and the heap can't be expanded.
84 // In both cases we want to retry the GC so that the initial mark pause is
85 // actually scheduled. In the second case, however, we should stall until
86 // until the GC locker is no longer active and then retry the initial mark GC.
87 _should_retry_gc = true;
88 }
89 }
90 return res;
91 }
92
93 void VM_G1IncCollectionPause::doit() {
94 G1CollectedHeap* g1h = G1CollectedHeap::heap();
95 assert(!_should_initiate_conc_mark ||
96 ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
97 (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) ||
98 _gc_cause == GCCause::_g1_humongous_allocation),
99 "only a GC locker, a System.gc() or a hum allocation induced GC should start a cycle");
100
101 if (_word_size > 0) {
102 // An allocation has been requested. So, try to do that first.
103 _result = g1h->attempt_allocation_at_safepoint(_word_size,
104 false /* expect_null_cur_alloc_region */);
105 if (_result != NULL) {
106 // If we can successfully allocate before we actually do the
107 // pause then we will consider this pause successful.
108 _pause_succeeded = true;
109 return;
110 }
111 }
112
113 GCCauseSetter x(g1h, _gc_cause);
114 if (_should_initiate_conc_mark) {
115 // It's safer to read old_marking_cycles_completed() here, given
116 // that noone else will be updating it concurrently. Since we'll
117 // only need it if we're initiating a marking cycle, no point in
118 // setting it earlier.
119 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
120
121 // At this point we are supposed to start a concurrent cycle. We
122 // will do so if one is not already in progress.
123 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
124
125 // The above routine returns true if we were able to force the
126 // next GC pause to be an initial mark; it returns false if a
127 // marking cycle is already in progress.
128 //
129 // If a marking cycle is already in progress just return and skip the
130 // pause below - if the reason for requesting this initial mark pause
131 // was due to a System.gc() then the requesting thread should block in
132 // doit_epilogue() until the marking cycle is complete.
133 //
134 // If this initial mark pause was requested as part of a humongous
135 // allocation then we know that the marking cycle must just have
136 // been started by another thread (possibly also allocating a humongous
137 // object) as there was no active marking cycle when the requesting
138 // thread checked before calling collect() in
139 // attempt_allocation_humongous(). Retrying the GC, in this case,
140 // will cause the requesting thread to spin inside collect() until the
141 // just started marking cycle is complete - which may be a while. So
142 // we do NOT retry the GC.
143 if (!res) {
144 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
145 if (_gc_cause != GCCause::_g1_humongous_allocation) {
146 _should_retry_gc = true;
147 }
148 return;
149 }
150 }
151
152 _pause_succeeded =
153 g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
154 if (_pause_succeeded && _word_size > 0) {
155 // An allocation had been requested.
156 _result = g1h->attempt_allocation_at_safepoint(_word_size,
157 true /* expect_null_cur_alloc_region */);
158 } else {
159 assert(_result == NULL, "invariant");
160 if (!_pause_succeeded) {
161 // Another possible reason reason for the pause to not be successful
162 // is that, again, the GC locker is active (and has become active
163 // since the prologue was executed). In this case we should retry
164 // the pause after waiting for the GC locker to become inactive.
165 _should_retry_gc = true;
166 }
167 }
168 }
169
170 void VM_G1IncCollectionPause::doit_epilogue() {
171 VM_GC_Operation::doit_epilogue();
172
173 // If the pause was initiated by a System.gc() and
174 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
175 // that just started (or maybe one that was already in progress) to
176 // finish.
177 if (_gc_cause == GCCause::_java_lang_system_gc &&
178 _should_initiate_conc_mark) {
179 assert(ExplicitGCInvokesConcurrent,
180 "the only way to be here is if ExplicitGCInvokesConcurrent is set");
181
182 G1CollectedHeap* g1h = G1CollectedHeap::heap();
183
184 // In the doit() method we saved g1h->old_marking_cycles_completed()
185 // in the _old_marking_cycles_completed_before field. We have to
186 // wait until we observe that g1h->old_marking_cycles_completed()
187 // has increased by at least one. This can happen if a) we started
188 // a cycle and it completes, b) a cycle already in progress
189 // completes, or c) a Full GC happens.
190
191 // If the condition has already been reached, there's no point in
192 // actually taking the lock and doing the wait.
193 if (g1h->old_marking_cycles_completed() <=
194 _old_marking_cycles_completed_before) {
195 // The following is largely copied from CMS
196
197 Thread* thr = Thread::current();
198 assert(thr->is_Java_thread(), "invariant");
199 JavaThread* jt = (JavaThread*)thr;
200 ThreadToNativeFromVM native(jt);
201
202 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
203 while (g1h->old_marking_cycles_completed() <=
204 _old_marking_cycles_completed_before) {
205 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
206 }
207 }
208 }
209 }
210
211 void VM_CGC_Operation::acquire_pending_list_lock() {
212 assert(_needs_pll, "don't call this otherwise");
213 // The caller may block while communicating
214 // with the SLT thread in order to acquire/release the PLL.
215 ConcurrentMarkThread::slt()->
216 manipulatePLL(SurrogateLockerThread::acquirePLL);
217 }
218
219 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
220 assert(_needs_pll, "don't call this otherwise");
221 // The caller may block while communicating
222 // with the SLT thread in order to acquire/release the PLL.
223 ConcurrentMarkThread::slt()->
224 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
225 }
226
227 void VM_CGC_Operation::doit() {
228 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
229 TraceTime t(_printGCMessage, G1Log::fine(), true, gclog_or_tty);
230 SharedHeap* sh = SharedHeap::heap();
231 // This could go away if CollectedHeap gave access to _gc_is_active...
232 if (sh != NULL) {
233 IsGCActiveMark x;
234 _cl->do_void();
235 } else {
236 _cl->do_void();
237 }
238 }
239
240 bool VM_CGC_Operation::doit_prologue() {
241 // Note the relative order of the locks must match that in
242 // VM_GC_Operation::doit_prologue() or deadlocks can occur
243 if (_needs_pll) {
244 acquire_pending_list_lock();
245 }
246
247 Heap_lock->lock();
248 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
249 return true;
250 }
251
252 void VM_CGC_Operation::doit_epilogue() {
253 // Note the relative order of the unlocks must match that in
254 // VM_GC_Operation::doit_epilogue()
255 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;
256 Heap_lock->unlock();
257 if (_needs_pll) {
258 release_and_notify_pending_list_lock();
259 }
260 }