1 /*
2 * Copyright (c) 2005, 2016, 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/allocTracer.hpp"
29 #include "gc/shared/gcId.hpp"
30 #include "gc/shared/gcLocker.inline.hpp"
31 #include "gc/shared/genCollectedHeap.hpp"
32 #include "gc/shared/vmGCOperations.hpp"
33 #include "logging/log.hpp"
34 #include "memory/oopFactory.hpp"
35 #include "runtime/handles.inline.hpp"
36 #include "runtime/init.hpp"
37 #include "runtime/interfaceSupport.hpp"
38 #include "utilities/dtrace.hpp"
39 #include "utilities/macros.hpp"
40 #include "utilities/preserveException.hpp"
41 #if INCLUDE_ALL_GCS
42 #include "gc/g1/g1CollectedHeap.inline.hpp"
43 #endif // INCLUDE_ALL_GCS
44
45 VM_GC_Operation::~VM_GC_Operation() {
46 CollectedHeap* ch = Universe::heap();
47 ch->collector_policy()->set_all_soft_refs_clear(false);
48 }
49
50 // The same dtrace probe can't be inserted in two different files, so we
51 // have to call it here, so it's only in one file. Can't create new probes
52 // for the other file anymore. The dtrace probes have to remain stable.
53 void VM_GC_Operation::notify_gc_begin(bool full) {
54 HOTSPOT_GC_BEGIN(
55 full);
56 HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
57 }
58
59 void VM_GC_Operation::notify_gc_end() {
60 HOTSPOT_GC_END();
61 HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
62 }
63
64 // Allocations may fail in several threads at about the same time,
65 // resulting in multiple gc requests. We only want to do one of them.
66 // In case a GC locker is active and the need for a GC is already signaled,
67 // we want to skip this GC attempt altogether, without doing a futile
68 // safepoint operation.
69 bool VM_GC_Operation::skip_operation() const {
70 bool skip = (_gc_count_before != Universe::heap()->total_collections());
71 if (_full && skip) {
72 skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
73 }
74 if (!skip && GCLocker::is_active_and_needs_gc()) {
75 skip = Universe::heap()->is_maximal_no_gc();
76 assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
77 "GCLocker cannot be active when initiating GC");
78 }
79 return skip;
80 }
81
82 bool VM_GC_Operation::doit_prologue() {
83 assert(Thread::current()->is_Java_thread(), "just checking");
84 assert(((_gc_cause != GCCause::_no_gc) &&
85 (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
86
87 // To be able to handle a GC the VM initialization needs to be completed.
88 if (!is_init_completed()) {
89 vm_exit_during_initialization(
90 err_msg("GC triggered before VM initialization completed. Try increasing "
91 "NewSize, current value " SIZE_FORMAT "%s.",
92 byte_size_in_proper_unit(NewSize),
93 proper_unit_for_byte_size(NewSize)));
94 }
95
96 // If the GC count has changed someone beat us to the collection
97 Heap_lock->lock();
98
99 // Check invocations
100 if (skip_operation()) {
101 // skip collection
102 Heap_lock->unlock();
103 _prologue_succeeded = false;
104 } else {
105 _prologue_succeeded = true;
106 }
107 return _prologue_succeeded;
108 }
109
110
111 void VM_GC_Operation::doit_epilogue() {
112 assert(Thread::current()->is_Java_thread(), "just checking");
113 if (Universe::has_reference_pending_list()) {
114 Heap_lock->notify_all();
115 }
116 Heap_lock->unlock();
117 }
118
119 bool VM_GC_HeapInspection::skip_operation() const {
120 return false;
121 }
122
123 bool VM_GC_HeapInspection::collect() {
124 if (GCLocker::is_active()) {
125 return false;
126 }
127 Universe::heap()->collect_as_vm_thread(GCCause::_heap_inspection);
128 return true;
129 }
130
131 void VM_GC_HeapInspection::doit() {
132 HandleMark hm;
133 Universe::heap()->ensure_parsability(false); // must happen, even if collection does
134 // not happen (e.g. due to GCLocker)
135 // or _full_gc being false
136 if (_full_gc) {
137 if (!collect()) {
138 // The collection attempt was skipped because the gc locker is held.
139 // The following dump may then be a tad misleading to someone expecting
140 // only live objects to show up in the dump (see CR 6944195). Just issue
141 // a suitable warning in that case and do not attempt to do a collection.
142 // The latter is a subtle point, because even a failed attempt
143 // to GC will, in fact, induce one in the future, which we
144 // probably want to avoid in this case because the GC that we may
145 // be about to attempt holds value for us only
146 // if it happens now and not if it happens in the eventual
147 // future.
148 log_warning(gc)("GC locker is held; pre-dump GC was skipped");
149 }
150 }
151 HeapInspection inspect(_csv_format, _print_help, _print_class_stats,
152 _columns);
153 inspect.heap_inspection(_out);
154 }
155
156
157 void VM_GenCollectForAllocation::doit() {
158 SvcGCMarker sgcm(SvcGCMarker::MINOR);
159
160 GenCollectedHeap* gch = GenCollectedHeap::heap();
161 GCCauseSetter gccs(gch, _gc_cause);
162 _result = gch->satisfy_failed_allocation(_word_size, _tlab);
163 assert(gch->is_in_reserved_or_null(_result), "result not in heap");
164
165 if (_result == NULL && GCLocker::is_active_and_needs_gc()) {
166 set_gc_locked();
167 }
168 }
169
170 void VM_GenCollectFull::doit() {
171 SvcGCMarker sgcm(SvcGCMarker::FULL);
172
173 GenCollectedHeap* gch = GenCollectedHeap::heap();
174 GCCauseSetter gccs(gch, _gc_cause);
175 gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_generation);
176 }
177
178 VM_CollectForMetadataAllocation::VM_CollectForMetadataAllocation(ClassLoaderData* loader_data,
179 size_t size,
180 Metaspace::MetadataType mdtype,
181 uint gc_count_before,
182 uint full_gc_count_before,
183 GCCause::Cause gc_cause)
184 : VM_GC_Operation(gc_count_before, gc_cause, full_gc_count_before, true),
185 _loader_data(loader_data), _size(size), _mdtype(mdtype), _result(NULL) {
186 assert(_size != 0, "An allocation should always be requested with this operation.");
187 AllocTracer::send_allocation_requiring_gc_event(_size * HeapWordSize, GCId::peek());
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 void VM_CollectForMetadataAllocation::doit() {
220 SvcGCMarker sgcm(SvcGCMarker::FULL);
221
222 CollectedHeap* heap = Universe::heap();
223 GCCauseSetter gccs(heap, _gc_cause);
224
225 // Check again if the space is available. Another thread
226 // may have similarly failed a metadata allocation and induced
227 // a GC that freed space for the allocation.
228 if (!MetadataAllocationFailALot) {
229 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
230 if (_result != NULL) {
231 return;
232 }
233 }
234
235 if (initiate_concurrent_GC()) {
236 // For CMS and G1 expand since the collection is going to be concurrent.
237 _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
238 if (_result != NULL) {
239 return;
240 }
241
242 log_debug(gc)("%s full GC for Metaspace", UseConcMarkSweepGC ? "CMS" : "G1");
243 }
244
245 // Don't clear the soft refs yet.
246 heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
247 // After a GC try to allocate without expanding. Could fail
248 // and expansion will be tried below.
249 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
250 if (_result != NULL) {
251 return;
252 }
253
254 // If still failing, allow the Metaspace to expand.
255 // See delta_capacity_until_GC() for explanation of the
256 // amount of the expansion.
257 // This should work unless there really is no more space
258 // or a MaxMetaspaceSize has been specified on the command line.
259 _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
260 if (_result != NULL) {
261 return;
262 }
263
264 // If expansion failed, do a collection clearing soft references.
265 heap->collect_as_vm_thread(GCCause::_metadata_GC_clear_soft_refs);
266 _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
267 if (_result != NULL) {
268 return;
269 }
270
271 log_debug(gc)("After Metaspace GC failed to allocate size " SIZE_FORMAT, _size);
272
273 if (GCLocker::is_active_and_needs_gc()) {
274 set_gc_locked();
275 }
276 }
277
278 VM_CollectForAllocation::VM_CollectForAllocation(size_t word_size, uint gc_count_before, GCCause::Cause cause)
279 : VM_GC_Operation(gc_count_before, cause), _result(NULL), _word_size(word_size) {
280 // Only report if operation was really caused by an allocation.
281 if (_word_size != 0) {
282 AllocTracer::send_allocation_requiring_gc_event(_word_size * HeapWordSize, GCId::peek());
283 }
284 }