1 /*
2 * Copyright (c) 2000, 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 "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc_interface/collectedHeap.inline.hpp"
30 #include "memory/sharedHeap.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/fprofiler.hpp"
33 #include "runtime/java.hpp"
34 #include "services/management.hpp"
35 #include "utilities/copy.hpp"
36 #include "utilities/workgroup.hpp"
37
38 SharedHeap* SharedHeap::_sh;
39
40 // The set of potentially parallel tasks in strong root scanning.
41 enum SH_process_strong_roots_tasks {
42 SH_PS_Universe_oops_do,
43 SH_PS_JNIHandles_oops_do,
44 SH_PS_ObjectSynchronizer_oops_do,
45 SH_PS_FlatProfiler_oops_do,
46 SH_PS_Management_oops_do,
47 SH_PS_SystemDictionary_oops_do,
48 SH_PS_jvmti_oops_do,
49 SH_PS_CodeCache_oops_do,
50 // Leave this one last.
51 SH_PS_NumElements
52 };
53
54 SharedHeap::SharedHeap(CollectorPolicy* policy_) :
55 CollectedHeap(),
56 _collector_policy(policy_),
57 _perm_gen(NULL), _rem_set(NULL),
58 _strong_roots_parity(0),
59 _process_strong_tasks(new SubTasksDone(SH_PS_NumElements)),
60 _workers(NULL)
61 {
62 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
63 vm_exit_during_initialization("Failed necessary allocation.");
64 }
65 _sh = this; // ch is static, should be set only once.
66 if ((UseParNewGC ||
67 (UseConcMarkSweepGC && (CMSParallelInitialMarkEnabled ||
68 CMSParallelRemarkEnabled)) ||
69 UseG1GC) &&
70 ParallelGCThreads > 0) {
71 _workers = new FlexibleWorkGang("Parallel GC Threads", ParallelGCThreads,
72 /* are_GC_task_threads */true,
73 /* are_ConcurrentGC_threads */false);
74 if (_workers == NULL) {
75 vm_exit_during_initialization("Failed necessary allocation.");
76 } else {
77 _workers->initialize_workers();
78 }
79 }
80 }
81
82 int SharedHeap::n_termination() {
83 return _process_strong_tasks->n_threads();
84 }
85
86 void SharedHeap::set_n_termination(int t) {
87 _process_strong_tasks->set_n_threads(t);
88 }
89
90 bool SharedHeap::heap_lock_held_for_gc() {
91 Thread* t = Thread::current();
92 return Heap_lock->owned_by_self()
93 || ( (t->is_GC_task_thread() || t->is_VM_thread())
94 && _thread_holds_heap_lock_for_gc);
95 }
96
97 void SharedHeap::set_par_threads(uint t) {
98 assert(t == 0 || !UseSerialGC, "Cannot have parallel threads");
99 _n_par_threads = t;
100 _process_strong_tasks->set_n_threads(t);
101 }
102
103 class AssertIsPermClosure: public OopClosure {
104 public:
105 virtual void do_oop(oop* p) {
106 assert((*p) == NULL || (*p)->is_perm(), "Referent should be perm.");
107 }
108 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
109 };
110 static AssertIsPermClosure assert_is_perm_closure;
111
112 #ifdef ASSERT
113 class AssertNonScavengableClosure: public OopClosure {
114 public:
115 virtual void do_oop(oop* p) {
116 assert(!Universe::heap()->is_in_partial_collection(*p),
117 "Referent should not be scavengable."); }
118 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
119 };
120 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
121 #endif
122
123 void SharedHeap::change_strong_roots_parity() {
124 // Also set the new collection parity.
125 assert(_strong_roots_parity >= 0 && _strong_roots_parity <= 2,
126 "Not in range.");
127 _strong_roots_parity++;
128 if (_strong_roots_parity == 3) _strong_roots_parity = 1;
129 assert(_strong_roots_parity >= 1 && _strong_roots_parity <= 2,
130 "Not in range.");
131 }
132
133 SharedHeap::StrongRootsScope::StrongRootsScope(SharedHeap* outer, bool activate)
134 : MarkScope(activate)
135 {
136 if (_active) {
137 outer->change_strong_roots_parity();
138 // Zero the claimed high water mark in the StringTable
139 StringTable::clear_parallel_claimed_index();
140 }
141 }
142
143 SharedHeap::StrongRootsScope::~StrongRootsScope() {
144 // nothing particular
145 }
146
147 void SharedHeap::process_strong_roots(bool activate_scope,
148 bool collecting_perm_gen,
149 ScanningOption so,
150 OopClosure* roots,
151 CodeBlobClosure* code_roots,
152 OopsInGenClosure* perm_blk,
153 bool manages_code_roots) {
154 StrongRootsScope srs(this, activate_scope);
155 // General strong roots.
156 assert(_strong_roots_parity != 0, "must have called prologue code");
157 // _n_termination for _process_strong_tasks should be set up stream
158 // in a method not running in a GC worker. Otherwise the GC worker
159 // could be trying to change the termination condition while the task
160 // is executing in another GC worker.
161 if (!_process_strong_tasks->is_task_claimed(SH_PS_Universe_oops_do)) {
162 Universe::oops_do(roots);
163 // Consider perm-gen discovered lists to be strong.
164 perm_gen()->ref_processor()->weak_oops_do(roots);
165 }
166 // Global (strong) JNI handles
167 if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do))
168 JNIHandles::oops_do(roots);
169
170 // All threads execute this; the individual threads are task groups.
171 if (CollectedHeap::use_parallel_gc_threads()) {
172 Threads::possibly_parallel_oops_do(roots, code_roots);
173 } else {
174 Threads::oops_do(roots, code_roots);
175 }
176
177 if (!_process_strong_tasks-> is_task_claimed(SH_PS_ObjectSynchronizer_oops_do))
178 ObjectSynchronizer::oops_do(roots);
179 if (!_process_strong_tasks->is_task_claimed(SH_PS_FlatProfiler_oops_do))
180 FlatProfiler::oops_do(roots);
181 if (!_process_strong_tasks->is_task_claimed(SH_PS_Management_oops_do))
182 Management::oops_do(roots);
183 if (!_process_strong_tasks->is_task_claimed(SH_PS_jvmti_oops_do))
184 JvmtiExport::oops_do(roots);
185
186 if (!_process_strong_tasks->is_task_claimed(SH_PS_SystemDictionary_oops_do)) {
187 if (so & SO_AllClasses) {
188 SystemDictionary::oops_do(roots);
189 } else if (so & SO_SystemClasses) {
190 SystemDictionary::always_strong_oops_do(roots);
191 }
192 }
193
194 // All threads execute the following. A specific chunk of buckets
195 // from the StringTable are the individual tasks.
196 if (so & SO_Strings || (!collecting_perm_gen && !JavaObjectsInPerm)) {
197 if (CollectedHeap::use_parallel_gc_threads()) {
198 StringTable::possibly_parallel_oops_do(roots);
199 } else {
200 StringTable::oops_do(roots);
201 }
202 }
203 if (JavaObjectsInPerm) {
204 // Verify the string table contents are in the perm gen
205 if (CollectedHeap::use_parallel_gc_threads()) {
206 NOT_PRODUCT(StringTable::possibly_parallel_oops_do(&assert_is_perm_closure));
207 } else {
208 NOT_PRODUCT(StringTable::oops_do(&assert_is_perm_closure));
209 }
210 }
211
212 if (!_process_strong_tasks->is_task_claimed(SH_PS_CodeCache_oops_do)) {
213 if (so & SO_CodeCache) {
214 // (Currently, CMSCollector uses this to do intermediate-strength collections.)
215 assert(collecting_perm_gen, "scanning all of code cache");
216 assert(code_roots != NULL, "must supply closure for code cache");
217 if (code_roots != NULL) {
218 CodeCache::blobs_do(code_roots);
219 }
220 } else if (so & (SO_SystemClasses|SO_AllClasses)) {
221 if (!manages_code_roots && !collecting_perm_gen) {
222 // If we are collecting from class statics, but we are not going to
223 // visit all of the CodeCache, collect from the non-perm roots if any.
224 // This makes the code cache function temporarily as a source of strong
225 // roots for oops, until the next major collection.
226 //
227 // If collecting_perm_gen is true, we require that this phase will call
228 // CodeCache::do_unloading. This will kill off nmethods with expired
229 // weak references, such as stale invokedynamic targets.
230 CodeCache::scavenge_root_nmethods_do(code_roots);
231 }
232 }
233 // Verify that the code cache contents are not subject to
234 // movement by a scavenging collection.
235 DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, /*do_marking=*/ false));
236 DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
237 }
238
239 if (!collecting_perm_gen) {
240 // All threads perform this; coordination is handled internally.
241
242 rem_set()->younger_refs_iterate(perm_gen(), perm_blk);
243 }
244 _process_strong_tasks->all_tasks_completed();
245 }
246
247 class AlwaysTrueClosure: public BoolObjectClosure {
248 public:
249 void do_object(oop p) { ShouldNotReachHere(); }
250 bool do_object_b(oop p) { return true; }
251 };
252 static AlwaysTrueClosure always_true;
253
254 class SkipAdjustingSharedStrings: public OopClosure {
255 OopClosure* _clo;
256 public:
257 SkipAdjustingSharedStrings(OopClosure* clo) : _clo(clo) {}
258
259 virtual void do_oop(oop* p) {
260 oop o = (*p);
261 if (!o->is_shared_readwrite()) {
262 _clo->do_oop(p);
263 }
264 }
265 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
266 };
267
268 // Unmarked shared Strings in the StringTable (which got there due to
269 // being in the constant pools of as-yet unloaded shared classes) were
270 // not marked and therefore did not have their mark words preserved.
271 // These entries are also deliberately not purged from the string
272 // table during unloading of unmarked strings. If an identity hash
273 // code was computed for any of these objects, it will not have been
274 // cleared to zero during the forwarding process or by the
275 // RecursiveAdjustSharedObjectClosure, and will be confused by the
276 // adjusting process as a forwarding pointer. We need to skip
277 // forwarding StringTable entries which contain unmarked shared
278 // Strings. Actually, since shared strings won't be moving, we can
279 // just skip adjusting any shared entries in the string table.
280
281 void SharedHeap::process_weak_roots(OopClosure* root_closure,
282 CodeBlobClosure* code_roots,
283 OopClosure* non_root_closure) {
284 // Global (weak) JNI handles
285 JNIHandles::weak_oops_do(&always_true, root_closure);
286
287 CodeCache::blobs_do(code_roots);
288 if (UseSharedSpaces && !DumpSharedSpaces) {
289 SkipAdjustingSharedStrings skip_closure(root_closure);
290 StringTable::oops_do(&skip_closure);
291 } else {
292 StringTable::oops_do(root_closure);
293 }
294 }
295
296 void SharedHeap::set_barrier_set(BarrierSet* bs) {
297 _barrier_set = bs;
298 // Cached barrier set for fast access in oops
299 oopDesc::set_bs(bs);
300 }
301
302 void SharedHeap::post_initialize() {
303 ref_processing_init();
304 }
305
306 void SharedHeap::ref_processing_init() {
307 perm_gen()->ref_processor_init();
308 }
309
310 // Some utilities.
311 void SharedHeap::print_size_transition(outputStream* out,
312 size_t bytes_before,
313 size_t bytes_after,
314 size_t capacity) {
315 out->print(" %d%s->%d%s(%d%s)",
316 byte_size_in_proper_unit(bytes_before),
317 proper_unit_for_byte_size(bytes_before),
318 byte_size_in_proper_unit(bytes_after),
319 proper_unit_for_byte_size(bytes_after),
320 byte_size_in_proper_unit(capacity),
321 proper_unit_for_byte_size(capacity));
322 }