1 /*
2 * Copyright (c) 2005, 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 "classfile/classLoader.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "gc/shared/gcLocker.inline.hpp"
29 #include "gc/shared/genCollectedHeap.hpp"
30 #include "gc/shared/vmGCOperations.hpp"
31 #include "memory/oopFactory.hpp"
32 #include "oops/instanceKlass.hpp"
33 #include "oops/instanceRefKlass.hpp"
34 #include "runtime/handles.inline.hpp"
35 #include "runtime/init.hpp"
36 #include "runtime/interfaceSupport.hpp"
37 #include "utilities/dtrace.hpp"
38 #include "utilities/macros.hpp"
39 #include "utilities/preserveException.hpp"
40 #if INCLUDE_ALL_GCS
41 #include "gc/g1/g1CollectedHeap.inline.hpp"
42 #endif // INCLUDE_ALL_GCS
43
44 VM_GC_Operation::~VM_GC_Operation() {
45 CollectedHeap* ch = Universe::heap();
46 ch->collector_policy()->set_all_soft_refs_clear(false);
47 }
48
49 // The same dtrace probe can't be inserted in two different files, so we
50 // have to call it here, so it's only in one file. Can't create new probes
51 // for the other file anymore. The dtrace probes have to remain stable.
52 void VM_GC_Operation::notify_gc_begin(bool full) {
53 HOTSPOT_GC_BEGIN(
54 full);
55 HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
56 }
57
58 void VM_GC_Operation::notify_gc_end() {
59 HOTSPOT_GC_END();
60 HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
61 }
62
63 void VM_GC_Operation::acquire_pending_list_lock() {
64 // we may enter this with pending exception set
65 InstanceRefKlass::acquire_pending_list_lock(&_pending_list_basic_lock);
66 }
67
68
69 void VM_GC_Operation::release_and_notify_pending_list_lock() {
70
71 InstanceRefKlass::release_and_notify_pending_list_lock(&_pending_list_basic_lock);
72 }
73
74 // Allocations may fail in several threads at about the same time,
75 // resulting in multiple gc requests. We only want to do one of them.
76 // In case a GC locker is active and the need for a GC is already signaled,
77 // we want to skip this GC attempt altogether, without doing a futile
78 // safepoint operation.
79 bool VM_GC_Operation::skip_operation() const {
80 bool skip = (_gc_count_before != Universe::heap()->total_collections());
81 if (_full && skip) {
82 skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
83 }
84 if (!skip && GC_locker::is_active_and_needs_gc()) {
85 skip = Universe::heap()->is_maximal_no_gc();
86 assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
87 "GC_locker cannot be active when initiating GC");
88 }
89 return skip;
90 }
91
92 bool VM_GC_Operation::doit_prologue() {
93 assert(Thread::current()->is_Java_thread(), "just checking");
94 assert(((_gc_cause != GCCause::_no_gc) &&
95 (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
96
97 // To be able to handle a GC the VM initialization needs to be completed.
98 if (!is_init_completed()) {
99 vm_exit_during_initialization(
100 err_msg("GC triggered before VM initialization completed. Try increasing "
101 "NewSize, current value " SIZE_FORMAT "%s.",
102 byte_size_in_proper_unit(NewSize),
103 proper_unit_for_byte_size(NewSize)));
104 }
105
106 acquire_pending_list_lock();
107 // If the GC count has changed someone beat us to the collection
108 // Get the Heap_lock after the pending_list_lock.
109 Heap_lock->lock();
110
111 // Check invocations
112 if (skip_operation()) {
113 // skip collection
114 Heap_lock->unlock();
115 release_and_notify_pending_list_lock();
116 _prologue_succeeded = false;
117 } else {
118 _prologue_succeeded = true;
119 }
120 return _prologue_succeeded;
121 }
122
123
124 void VM_GC_Operation::doit_epilogue() {
125 assert(Thread::current()->is_Java_thread(), "just checking");
126 // Release the Heap_lock first.
127 Heap_lock->unlock();
128 release_and_notify_pending_list_lock();
129 }
130
131 bool VM_GC_HeapInspection::skip_operation() const {
132 return false;
133 }
134
135 bool VM_GC_HeapInspection::collect() {
136 if (GC_locker::is_active()) {
137 return false;
138 }
139 Universe::heap()->collect_as_vm_thread(GCCause::_heap_inspection);
140 return true;
141 }
142
143 void VM_GC_HeapInspection::doit() {
144 HandleMark hm;
145 Universe::heap()->ensure_parsability(false); // must happen, even if collection does
146 // not happen (e.g. due to GC_locker)
147 // or _full_gc being false
148 if (_full_gc) {
149 if (!collect()) {
150 // The collection attempt was skipped because the gc locker is held.
151 // The following dump may then be a tad misleading to someone expecting
152 // only live objects to show up in the dump (see CR 6944195). Just issue
153 // a suitable warning in that case and do not attempt to do a collection.
154 // The latter is a subtle point, because even a failed attempt
155 // to GC will, in fact, induce one in the future, which we
156 // probably want to avoid in this case because the GC that we may
157 // be about to attempt holds value for us only
158 // if it happens now and not if it happens in the eventual
159 // future.
160 warning("GC locker is held; pre-dump GC was skipped");
161 }
162 }
163 HeapInspection inspect(_csv_format, _print_help, _print_class_stats,
164 _columns);
165 inspect.heap_inspection(_out);
166 }
167
168
169 void VM_GenCollectForAllocation::doit() {
170 SvcGCMarker sgcm(SvcGCMarker::MINOR);
171
172 GenCollectedHeap* gch = GenCollectedHeap::heap();
173 GCCauseSetter gccs(gch, _gc_cause);
174 _result = gch->satisfy_failed_allocation(_word_size, _tlab);
175 assert(gch->is_in_reserved_or_null(_result), "result not in heap");
176
177 if (_result == NULL && GC_locker::is_active_and_needs_gc()) {
178 set_gc_locked();
179 }
180 }
181
182 void VM_GenCollectFull::doit() {
183 SvcGCMarker sgcm(SvcGCMarker::FULL);
184
185 GenCollectedHeap* gch = GenCollectedHeap::heap();
186 GCCauseSetter gccs(gch, _gc_cause);
187 gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_generation);
188 }
189
190 // Returns true iff concurrent GCs unloads metadata.
191 bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
192 #if INCLUDE_ALL_GCS
193 if (UseConcMarkSweepGC && CMSClassUnloadingEnabled) {
194 MetaspaceGC::set_should_concurrent_collect(true);
195 return true;
196 }
197
198 if (UseG1GC && ClassUnloadingWithConcurrentMark) {
199 G1CollectedHeap* g1h = G1CollectedHeap::heap();
200 g1h->g1_policy()->collector_state()->set_initiate_conc_mark_if_possible(true);
201
202 GCCauseSetter x(g1h, _gc_cause);
203
204 // At this point we are supposed to start a concurrent cycle. We
205 // will do so if one is not already in progress.
206 bool should_start = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
207
208 if (should_start) {
209 double pause_target = g1h->g1_policy()->max_pause_time_ms();
210 g1h->do_collection_pause_at_safepoint(pause_target);
211 }
212 return true;
213 }
214 #endif
215
216 return false;
217 }
218
219 static void log_metaspace_alloc_failure_for_concurrent_GC() {
220 if (Verbose && PrintGCDetails) {
221 if (UseConcMarkSweepGC) {
222 gclog_or_tty->print_cr("\nCMS full GC for Metaspace");
223 } else if (UseG1GC) {
224 gclog_or_tty->print_cr("\nG1 full GC for Metaspace");
225 }
226 }
227 }
228
229 void VM_CollectForMetadataAllocation::doit() {
230 SvcGCMarker sgcm(SvcGCMarker::FULL);
231
232 CollectedHeap* heap = Universe::heap();
233 GCCauseSetter gccs(heap, _gc_cause);
234
235 // Check again if the space is available. Another thread
236 // may have similarly failed a metadata allocation and induced
237 // a GC that freed space for the allocation.
238 if (!MetadataAllocationFailALot) {
239 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
240 if (_result != NULL) {
241 return;
242 }
243 }
244
245 if (initiate_concurrent_GC()) {
246 // For CMS and G1 expand since the collection is going to be concurrent.
247 _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
248 if (_result != NULL) {
249 return;
250 }
251
252 log_metaspace_alloc_failure_for_concurrent_GC();
253 }
254
255 // Don't clear the soft refs yet.
256 heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
257 // After a GC try to allocate without expanding. Could fail
258 // and expansion will be tried below.
259 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
260 if (_result != NULL) {
261 return;
262 }
263
264 // If still failing, allow the Metaspace to expand.
265 // See delta_capacity_until_GC() for explanation of the
266 // amount of the expansion.
267 // This should work unless there really is no more space
268 // or a MaxMetaspaceSize has been specified on the command line.
269 _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
270 if (_result != NULL) {
271 return;
272 }
273
274 // If expansion failed, do a last-ditch collection and try allocating
275 // again. A last-ditch collection will clear softrefs. This
276 // behavior is similar to the last-ditch collection done for perm
277 // gen when it was full and a collection for failed allocation
278 // did not free perm gen space.
279 heap->collect_as_vm_thread(GCCause::_last_ditch_collection);
280 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
281 if (_result != NULL) {
282 return;
283 }
284
285 if (Verbose && PrintGCDetails) {
286 gclog_or_tty->print_cr("\nAfter Metaspace GC failed to allocate size "
287 SIZE_FORMAT, _size);
288 }
289
290 if (GC_locker::is_active_and_needs_gc()) {
291 set_gc_locked();
292 }
293 }