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 */
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/gcTimer.hpp"
32 #include "gc_implementation/shared/gcTraceTime.hpp"
33 #include "gc_implementation/shared/isGCActiveMark.hpp"
34 #include "gc_implementation/g1/vm_operations_g1.hpp"
35 #include "runtime/interfaceSupport.hpp"
36
37 VM_G1CollectForAllocation::VM_G1CollectForAllocation(
38 unsigned int gc_count_before,
39 size_t word_size)
40 : VM_G1OperationWithAllocRequest(gc_count_before, word_size,
41 GCCause::_allocation_failure) {
42 guarantee(word_size > 0, "an allocation should always be requested");
43 }
44
45 void VM_G1CollectForAllocation::doit() {
46 G1CollectedHeap* g1h = G1CollectedHeap::heap();
47 GCCauseSetter x(g1h, _gc_cause);
48 _result = g1h->satisfy_failed_allocation(_word_size, &_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(
60 unsigned int gc_count_before,
61 size_t word_size,
62 bool should_initiate_conc_mark,
63 double target_pause_time_ms,
64 GCCause::Cause gc_cause)
65 : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),
66 _should_initiate_conc_mark(should_initiate_conc_mark),
67 _target_pause_time_ms(target_pause_time_ms),
68 _should_retry_gc(false),
69 _old_marking_cycles_completed_before(0) {
70 guarantee(target_pause_time_ms > 0.0,
71 err_msg("target_pause_time_ms = %1.6lf should be positive",
72 target_pause_time_ms));
73 guarantee(word_size == 0 || gc_cause == GCCause::_g1_inc_collection_pause,
74 "we can only request an allocation if the GC cause is for "
75 "an incremental GC pause");
76 _gc_cause = gc_cause;
77 }
78
79 bool VM_G1IncCollectionPause::doit_prologue() {
80 bool res = VM_GC_Operation::doit_prologue();
81 if (!res) {
82 if (_should_initiate_conc_mark) {
83 // The prologue can fail for a couple of reasons. The first is that another GC
84 // got scheduled and prevented the scheduling of the initial mark GC. The
85 // second is that the GC locker may be active and the heap can't be expanded.
86 // In both cases we want to retry the GC so that the initial mark pause is
87 // actually scheduled. In the second case, however, we should stall until
88 // until the GC locker is no longer active and then retry the initial mark GC.
89 _should_retry_gc = true;
90 }
91 }
92 return res;
93 }
94
95 void VM_G1IncCollectionPause::doit() {
96 G1CollectedHeap* g1h = G1CollectedHeap::heap();
97 assert(!_should_initiate_conc_mark ||
98 ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
99 (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) ||
100 _gc_cause == GCCause::_g1_humongous_allocation),
101 "only a GC locker, a System.gc() or a hum allocation induced GC should start a cycle");
102
103 if (_word_size > 0) {
104 // An allocation has been requested. So, try to do that first.
105 _result = g1h->attempt_allocation_at_safepoint(_word_size,
106 false /* expect_null_cur_alloc_region */);
107 if (_result != NULL) {
108 // If we can successfully allocate before we actually do the
109 // pause then we will consider this pause successful.
110 _pause_succeeded = true;
111 return;
112 }
113 }
114
115 GCCauseSetter x(g1h, _gc_cause);
116 if (_should_initiate_conc_mark) {
117 // It's safer to read old_marking_cycles_completed() here, given
118 // that noone else will be updating it concurrently. Since we'll
119 // only need it if we're initiating a marking cycle, no point in
120 // setting it earlier.
121 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
122
123 // At this point we are supposed to start a concurrent cycle. We
124 // will do so if one is not already in progress.
125 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
126
127 // The above routine returns true if we were able to force the
128 // next GC pause to be an initial mark; it returns false if a
129 // marking cycle is already in progress.
130 //
131 // If a marking cycle is already in progress just return and skip the
132 // pause below - if the reason for requesting this initial mark pause
133 // was due to a System.gc() then the requesting thread should block in
134 // doit_epilogue() until the marking cycle is complete.
135 //
136 // If this initial mark pause was requested as part of a humongous
137 // allocation then we know that the marking cycle must just have
138 // been started by another thread (possibly also allocating a humongous
139 // object) as there was no active marking cycle when the requesting
140 // thread checked before calling collect() in
141 // attempt_allocation_humongous(). Retrying the GC, in this case,
142 // will cause the requesting thread to spin inside collect() until the
143 // just started marking cycle is complete - which may be a while. So
144 // we do NOT retry the GC.
145 if (!res) {
146 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
147 if (_gc_cause != GCCause::_g1_humongous_allocation) {
148 _should_retry_gc = true;
149 }
150 return;
151 }
152 }
153
154 _pause_succeeded =
155 g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
156 if (_pause_succeeded && _word_size > 0) {
157 // An allocation had been requested.
158 _result = g1h->attempt_allocation_at_safepoint(_word_size,
159 true /* expect_null_cur_alloc_region */);
160 } else {
161 assert(_result == NULL, "invariant");
162 if (!_pause_succeeded) {
163 // Another possible reason reason for the pause to not be successful
164 // is that, again, the GC locker is active (and has become active
165 // since the prologue was executed). In this case we should retry
166 // the pause after waiting for the GC locker to become inactive.
167 _should_retry_gc = true;
168 }
169 }
170 }
171
172 void VM_G1IncCollectionPause::doit_epilogue() {
173 VM_GC_Operation::doit_epilogue();
174
175 // If the pause was initiated by a System.gc() and
176 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
177 // that just started (or maybe one that was already in progress) to
178 // finish.
179 if (_gc_cause == GCCause::_java_lang_system_gc &&
180 _should_initiate_conc_mark) {
181 assert(ExplicitGCInvokesConcurrent,
182 "the only way to be here is if ExplicitGCInvokesConcurrent is set");
183
184 G1CollectedHeap* g1h = G1CollectedHeap::heap();
185
186 // In the doit() method we saved g1h->old_marking_cycles_completed()
187 // in the _old_marking_cycles_completed_before field. We have to
188 // wait until we observe that g1h->old_marking_cycles_completed()
189 // has increased by at least one. This can happen if a) we started
190 // a cycle and it completes, b) a cycle already in progress
191 // completes, or c) a Full GC happens.
192
193 // If the condition has already been reached, there's no point in
194 // actually taking the lock and doing the wait.
195 if (g1h->old_marking_cycles_completed() <=
196 _old_marking_cycles_completed_before) {
197 // The following is largely copied from CMS
198
199 Thread* thr = Thread::current();
200 assert(thr->is_Java_thread(), "invariant");
201 JavaThread* jt = (JavaThread*)thr;
202 ThreadToNativeFromVM native(jt);
203
204 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
205 while (g1h->old_marking_cycles_completed() <=
206 _old_marking_cycles_completed_before) {
207 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
208 }
209 }
210 }
211 }
212
213 void VM_CGC_Operation::acquire_pending_list_lock() {
214 assert(_needs_pll, "don't call this otherwise");
215 // The caller may block while communicating
216 // with the SLT thread in order to acquire/release the PLL.
217 ConcurrentMarkThread::slt()->
218 manipulatePLL(SurrogateLockerThread::acquirePLL);
219 }
220
221 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
222 assert(_needs_pll, "don't call this otherwise");
223 // The caller may block while communicating
224 // with the SLT thread in order to acquire/release the PLL.
225 ConcurrentMarkThread::slt()->
226 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
227 }
228
229 void VM_CGC_Operation::doit() {
230 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
231 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
232 GCTraceTime t(_printGCMessage, G1Log::fine(), true, G1CollectedHeap::heap()->gc_timer_cm());
233 SharedHeap* sh = SharedHeap::heap();
234 // This could go away if CollectedHeap gave access to _gc_is_active...
235 if (sh != NULL) {
236 IsGCActiveMark x;
237 _cl->do_void();
238 } else {
239 _cl->do_void();
240 }
241 }
242
243 bool VM_CGC_Operation::doit_prologue() {
244 // Note the relative order of the locks must match that in
245 // VM_GC_Operation::doit_prologue() or deadlocks can occur
246 if (_needs_pll) {
247 acquire_pending_list_lock();
248 }
249
250 Heap_lock->lock();
251 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
252 return true;
253 }
254
255 void VM_CGC_Operation::doit_epilogue() {
256 // Note the relative order of the unlocks must match that in
257 // VM_GC_Operation::doit_epilogue()
258 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;
259 Heap_lock->unlock();
260 if (_needs_pll) {
261 release_and_notify_pending_list_lock();
262 }
263 }