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