1 /*
2 * Copyright (c) 2005, 2014, 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_implementation/shared/vmGCOperations.hpp"
29 #include "memory/gcLocker.inline.hpp"
30 #include "memory/genCollectedHeap.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/preserveException.hpp"
39 #include "utilities/macros.hpp"
40 #if INCLUDE_ALL_GCS
41 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
42 #endif // INCLUDE_ALL_GCS
43
44 // The same dtrace probe can't be inserted in two different files, so we
45 // have to call it here, so it's only in one file. Can't create new probes
46 // for the other file anymore. The dtrace probes have to remain stable.
47 void VM_GC_Operation::notify_gc_begin(bool full) {
48 HOTSPOT_GC_BEGIN(
49 full);
50 HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
51 }
52
53 void VM_GC_Operation::notify_gc_end() {
54 HOTSPOT_GC_END();
55 HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
56 }
57
58 void VM_GC_Operation::acquire_pending_list_lock() {
59 // we may enter this with pending exception set
60 InstanceRefKlass::acquire_pending_list_lock(&_pending_list_basic_lock);
61 }
62
63
64 void VM_GC_Operation::release_and_notify_pending_list_lock() {
65
66 InstanceRefKlass::release_and_notify_pending_list_lock(&_pending_list_basic_lock);
67 }
68
69 // Allocations may fail in several threads at about the same time,
70 // resulting in multiple gc requests. We only want to do one of them.
71 // In case a GC locker is active and the need for a GC is already signaled,
72 // we want to skip this GC attempt altogether, without doing a futile
73 // safepoint operation.
74 bool VM_GC_Operation::skip_operation() const {
75 bool skip = (_gc_count_before != Universe::heap()->total_collections());
76 if (_full && skip) {
77 skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
78 }
79 if (!skip && GC_locker::is_active_and_needs_gc()) {
80 skip = Universe::heap()->is_maximal_no_gc();
81 assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
82 "GC_locker cannot be active when initiating GC");
83 }
84 return skip;
85 }
86
87 bool VM_GC_Operation::doit_prologue() {
88 assert(Thread::current()->is_Java_thread(), "just checking");
89 assert(((_gc_cause != GCCause::_no_gc) &&
90 (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
91
92 // To be able to handle a GC the VM initialization needs to be completed.
93 if (!is_init_completed()) {
94 vm_exit_during_initialization(
95 err_msg("GC triggered before VM initialization completed. Try increasing "
96 "NewSize, current value " UINTX_FORMAT "%s.",
97 byte_size_in_proper_unit(NewSize),
98 proper_unit_for_byte_size(NewSize)));
99 }
100
101 acquire_pending_list_lock();
102 // If the GC count has changed someone beat us to the collection
103 // Get the Heap_lock after the pending_list_lock.
104 Heap_lock->lock();
105
106 // Check invocations
107 if (skip_operation()) {
108 // skip collection
109 Heap_lock->unlock();
110 release_and_notify_pending_list_lock();
111 _prologue_succeeded = false;
112 } else {
113 _prologue_succeeded = true;
114 SharedHeap* sh = SharedHeap::heap();
115 if (sh != NULL) sh->_thread_holds_heap_lock_for_gc = true;
116 }
117 return _prologue_succeeded;
118 }
119
120
121 void VM_GC_Operation::doit_epilogue() {
122 assert(Thread::current()->is_Java_thread(), "just checking");
123 // Release the Heap_lock first.
124 SharedHeap* sh = SharedHeap::heap();
125 if (sh != NULL) sh->_thread_holds_heap_lock_for_gc = false;
126 Heap_lock->unlock();
127 release_and_notify_pending_list_lock();
128 }
129
130 bool VM_GC_HeapInspection::doit_prologue() {
131 if (Universe::heap()->supports_heap_inspection()) {
132 return VM_GC_Operation::doit_prologue();
133 } else {
134 return false;
135 }
136 }
137
138 bool VM_GC_HeapInspection::skip_operation() const {
139 assert(Universe::heap()->supports_heap_inspection(), "huh?");
140 return false;
141 }
142
143 bool VM_GC_HeapInspection::collect() {
144 if (GC_locker::is_active()) {
145 return false;
146 }
147 Universe::heap()->collect_as_vm_thread(GCCause::_heap_inspection);
148 return true;
149 }
150
151 void VM_GC_HeapInspection::doit() {
152 HandleMark hm;
153 Universe::heap()->ensure_parsability(false); // must happen, even if collection does
154 // not happen (e.g. due to GC_locker)
155 // or _full_gc being false
156 if (_full_gc) {
157 if (!collect()) {
158 // The collection attempt was skipped because the gc locker is held.
159 // The following dump may then be a tad misleading to someone expecting
160 // only live objects to show up in the dump (see CR 6944195). Just issue
161 // a suitable warning in that case and do not attempt to do a collection.
162 // The latter is a subtle point, because even a failed attempt
163 // to GC will, in fact, induce one in the future, which we
164 // probably want to avoid in this case because the GC that we may
165 // be about to attempt holds value for us only
166 // if it happens now and not if it happens in the eventual
167 // future.
168 warning("GC locker is held; pre-dump GC was skipped");
169 }
170 }
171 HeapInspection inspect(_csv_format, _print_help, _print_class_stats,
172 _columns);
173 inspect.heap_inspection(_out);
174 }
175
176
177 void VM_GenCollectForAllocation::doit() {
178 SvcGCMarker sgcm(SvcGCMarker::MINOR);
179
180 GenCollectedHeap* gch = GenCollectedHeap::heap();
181 GCCauseSetter gccs(gch, _gc_cause);
182 _res = gch->satisfy_failed_allocation(_size, _tlab);
183 assert(gch->is_in_reserved_or_null(_res), "result not in heap");
184
185 if (_res == NULL && GC_locker::is_active_and_needs_gc()) {
186 set_gc_locked();
187 }
188 }
189
190 void VM_GenCollectFull::doit() {
191 SvcGCMarker sgcm(SvcGCMarker::FULL);
192
193 GenCollectedHeap* gch = GenCollectedHeap::heap();
194 GCCauseSetter gccs(gch, _gc_cause);
195 gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_level);
196 }
197
198 // Returns true iff concurrent GCs unloads metadata.
199 bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
200 #if INCLUDE_ALL_GCS
201 if (UseConcMarkSweepGC && CMSClassUnloadingEnabled) {
202 MetaspaceGC::set_should_concurrent_collect(true);
203 return true;
204 }
205
206 if (UseG1GC && ClassUnloadingWithConcurrentMark) {
207 G1CollectedHeap* g1h = G1CollectedHeap::heap();
208 g1h->g1_policy()->set_initiate_conc_mark_if_possible();
209
210 GCCauseSetter x(g1h, _gc_cause);
211
212 // At this point we are supposed to start a concurrent cycle. We
213 // will do so if one is not already in progress.
214 bool should_start = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
215
216 if (should_start) {
217 double pause_target = g1h->g1_policy()->max_pause_time_ms();
218 g1h->do_collection_pause_at_safepoint(pause_target);
219 }
220 return true;
221 }
222 #endif
223
224 return false;
225 }
226
227 static void log_metaspace_alloc_failure_for_concurrent_GC() {
228 if (Verbose && PrintGCDetails) {
229 if (UseConcMarkSweepGC) {
230 gclog_or_tty->print_cr("\nCMS full GC for Metaspace");
231 } else if (UseG1GC) {
232 gclog_or_tty->print_cr("\nG1 full GC for Metaspace");
233 }
234 }
235 }
236
237 void VM_CollectForMetadataAllocation::doit() {
238 SvcGCMarker sgcm(SvcGCMarker::FULL);
239
240 CollectedHeap* heap = Universe::heap();
241 GCCauseSetter gccs(heap, _gc_cause);
242
243 // Check again if the space is available. Another thread
244 // may have similarly failed a metadata allocation and induced
245 // a GC that freed space for the allocation.
246 if (!MetadataAllocationFailALot) {
247 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
248 if (_result != NULL) {
249 return;
250 }
251 }
252
253 if (initiate_concurrent_GC()) {
254 // For CMS and G1 expand since the collection is going to be concurrent.
255 _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
256 if (_result != NULL) {
257 return;
258 }
259
260 log_metaspace_alloc_failure_for_concurrent_GC();
261 }
262
263 // Don't clear the soft refs yet.
264 heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
265 // After a GC try to allocate without expanding. Could fail
266 // and expansion will be tried below.
267 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
268 if (_result != NULL) {
269 return;
270 }
271
272 // If still failing, allow the Metaspace to expand.
273 // See delta_capacity_until_GC() for explanation of the
274 // amount of the expansion.
275 // This should work unless there really is no more space
276 // or a MaxMetaspaceSize has been specified on the command line.
277 _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
278 if (_result != NULL) {
279 return;
280 }
281
282 // If expansion failed, do a last-ditch collection and try allocating
283 // again. A last-ditch collection will clear softrefs. This
284 // behavior is similar to the last-ditch collection done for perm
285 // gen when it was full and a collection for failed allocation
286 // did not free perm gen space.
287 heap->collect_as_vm_thread(GCCause::_last_ditch_collection);
288 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
289 if (_result != NULL) {
290 return;
291 }
292
293 if (Verbose && PrintGCDetails) {
294 gclog_or_tty->print_cr("\nAfter Metaspace GC failed to allocate size "
295 SIZE_FORMAT, _size);
296 }
297
298 if (GC_locker::is_active_and_needs_gc()) {
299 set_gc_locked();
300 }
301 }