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
49 _result = g1h->satisfy_failed_allocation(_word_size, allocation_context(), &_pause_succeeded);
50 assert(_result == NULL || _pause_succeeded,
51 "if we get back a result, the pause should have succeeded");
52 }
53
54 void VM_G1CollectFull::doit() {
55 G1CollectedHeap* g1h = G1CollectedHeap::heap();
56 GCCauseSetter x(g1h, _gc_cause);
57 g1h->do_full_collection(false /* clear_all_soft_refs */);
58 }
59
60 VM_G1IncCollectionPause::VM_G1IncCollectionPause(
61 unsigned int gc_count_before,
62 size_t word_size,
63 bool should_initiate_conc_mark,
64 double target_pause_time_ms,
65 GCCause::Cause gc_cause)
66 : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),
67 _should_initiate_conc_mark(should_initiate_conc_mark),
68 _target_pause_time_ms(target_pause_time_ms),
69 _should_retry_gc(false),
70 _old_marking_cycles_completed_before(0) {
71 guarantee(target_pause_time_ms > 0.0,
72 err_msg("target_pause_time_ms = %1.6lf should be positive",
73 target_pause_time_ms));
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 _gc_cause == GCCause::_update_allocation_context_stats_inc),
100 "only a GC locker, a System.gc(), stats update or a hum allocation induced GC should start a cycle");
101
102 if (_word_size > 0) {
103 // An allocation has been requested. So, try to do that first.
104 _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),
105 false /* expect_null_cur_alloc_region */);
106 if (_result != NULL) {
107 // If we can successfully allocate before we actually do the
108 // pause then we will consider this pause successful.
109 _pause_succeeded = true;
110 return;
111 }
112 }
113
114 GCCauseSetter x(g1h, _gc_cause);
115 if (_should_initiate_conc_mark) {
116 // It's safer to read old_marking_cycles_completed() here, given
117 // that noone else will be updating it concurrently. Since we'll
118 // only need it if we're initiating a marking cycle, no point in
119 // setting it earlier.
120 _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
121
122 // At this point we are supposed to start a concurrent cycle. We
123 // will do so if one is not already in progress.
124 bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
125
126 // The above routine returns true if we were able to force the
127 // next GC pause to be an initial mark; it returns false if a
128 // marking cycle is already in progress.
129 //
130 // If a marking cycle is already in progress just return and skip the
131 // pause below - if the reason for requesting this initial mark pause
132 // was due to a System.gc() then the requesting thread should block in
133 // doit_epilogue() until the marking cycle is complete.
134 //
135 // If this initial mark pause was requested as part of a humongous
136 // allocation then we know that the marking cycle must just have
137 // been started by another thread (possibly also allocating a humongous
138 // object) as there was no active marking cycle when the requesting
139 // thread checked before calling collect() in
140 // attempt_allocation_humongous(). Retrying the GC, in this case,
141 // will cause the requesting thread to spin inside collect() until the
142 // just started marking cycle is complete - which may be a while. So
143 // we do NOT retry the GC.
144 if (!res) {
145 assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
146 if (_gc_cause != GCCause::_g1_humongous_allocation) {
147 _should_retry_gc = true;
148 }
149 return;
150 }
151 }
152
153 _pause_succeeded =
154 g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
155 if (_pause_succeeded && _word_size > 0) {
156 // An allocation had been requested.
157 _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),
158 true /* expect_null_cur_alloc_region */);
159 } else {
160 assert(_result == NULL, "invariant");
161 if (!_pause_succeeded) {
162 // Another possible reason reason for the pause to not be successful
163 // is that, again, the GC locker is active (and has become active
164 // since the prologue was executed). In this case we should retry
165 // the pause after waiting for the GC locker to become inactive.
166 _should_retry_gc = true;
167 }
168 }
169 }
170
171 void VM_G1IncCollectionPause::doit_epilogue() {
172 VM_GC_Operation::doit_epilogue();
173
174 // If the pause was initiated by a System.gc() and
175 // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
176 // that just started (or maybe one that was already in progress) to
177 // finish.
178 if (_gc_cause == GCCause::_java_lang_system_gc &&
179 _should_initiate_conc_mark) {
180 assert(ExplicitGCInvokesConcurrent,
181 "the only way to be here is if ExplicitGCInvokesConcurrent is set");
182
183 G1CollectedHeap* g1h = G1CollectedHeap::heap();
184
185 // In the doit() method we saved g1h->old_marking_cycles_completed()
186 // in the _old_marking_cycles_completed_before field. We have to
187 // wait until we observe that g1h->old_marking_cycles_completed()
188 // has increased by at least one. This can happen if a) we started
189 // a cycle and it completes, b) a cycle already in progress
190 // completes, or c) a Full GC happens.
191
192 // If the condition has already been reached, there's no point in
193 // actually taking the lock and doing the wait.
194 if (g1h->old_marking_cycles_completed() <=
195 _old_marking_cycles_completed_before) {
196 // The following is largely copied from CMS
197
198 Thread* thr = Thread::current();
199 assert(thr->is_Java_thread(), "invariant");
200 JavaThread* jt = (JavaThread*)thr;
201 ThreadToNativeFromVM native(jt);
202
203 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
204 while (g1h->old_marking_cycles_completed() <=
205 _old_marking_cycles_completed_before) {
206 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
207 }
208 }
209 }
210 }
211
212 void VM_CGC_Operation::acquire_pending_list_lock() {
213 assert(_needs_pll, "don't call this otherwise");
214 // The caller may block while communicating
215 // with the SLT thread in order to acquire/release the PLL.
216 SurrogateLockerThread* slt = ConcurrentMarkThread::slt();
217 if (slt != NULL) {
218 slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
219 } else {
220 SurrogateLockerThread::report_missing_slt();
221 }
222 }
223
224 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
225 assert(_needs_pll, "don't call this otherwise");
226 // The caller may block while communicating
227 // with the SLT thread in order to acquire/release the PLL.
228 ConcurrentMarkThread::slt()->
229 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
230 }
231
232 void VM_CGC_Operation::doit() {
233 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
234 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
235 GCTraceTime t(_printGCMessage, G1Log::fine(), true, G1CollectedHeap::heap()->gc_timer_cm(), G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id());
236 SharedHeap* sh = SharedHeap::heap();
237 // This could go away if CollectedHeap gave access to _gc_is_active...
238 if (sh != NULL) {
239 IsGCActiveMark x;
240 _cl->do_void();
241 } else {
242 _cl->do_void();
243 }
244 }
245
246 bool VM_CGC_Operation::doit_prologue() {
247 // Note the relative order of the locks must match that in
248 // VM_GC_Operation::doit_prologue() or deadlocks can occur
249 if (_needs_pll) {
250 acquire_pending_list_lock();
251 }
252
253 Heap_lock->lock();
254 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
255 return true;
256 }
257
258 void VM_CGC_Operation::doit_epilogue() {
259 // Note the relative order of the unlocks must match that in
260 // VM_GC_Operation::doit_epilogue()
261 SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;
262 Heap_lock->unlock();
263 if (_needs_pll) {
264 release_and_notify_pending_list_lock();
265 }
266 }