1 /*
2 * Copyright (c) 2000, 2010, 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 #ifndef SHARE_VM_MEMORY_SHAREDHEAP_HPP
26 #define SHARE_VM_MEMORY_SHAREDHEAP_HPP
27
28 #include "gc_interface/collectedHeap.hpp"
29 #include "memory/generation.hpp"
30 #include "memory/permGen.hpp"
31
32 // A "SharedHeap" is an implementation of a java heap for HotSpot. This
33 // is an abstract class: there may be many different kinds of heaps. This
34 // class defines the functions that a heap must implement, and contains
35 // infrastructure common to all heaps.
36
37 class PermGen;
38 class Generation;
39 class BarrierSet;
40 class GenRemSet;
41 class Space;
42 class SpaceClosure;
43 class OopClosure;
44 class OopsInGenClosure;
45 class ObjectClosure;
46 class SubTasksDone;
47 class WorkGang;
48 class CollectorPolicy;
49 class KlassHandle;
50
51 class SharedHeap : public CollectedHeap {
52 friend class VMStructs;
53
54 friend class VM_GC_Operation;
55 friend class VM_CGC_Operation;
56
57 private:
58 // For claiming strong_roots tasks.
59 SubTasksDone* _process_strong_tasks;
60
61 protected:
62 // There should be only a single instance of "SharedHeap" in a program.
63 // This is enforced with the protected constructor below, which will also
64 // set the static pointer "_sh" to that instance.
65 static SharedHeap* _sh;
66
67 // All heaps contain a "permanent generation." This is some ways
68 // similar to a generation in a generational system, in other ways not.
69 // See the "PermGen" class.
70 PermGen* _perm_gen;
71
72 // and the Gen Remembered Set, at least one good enough to scan the perm
73 // gen.
74 GenRemSet* _rem_set;
75
76 // A gc policy, controls global gc resource issues
77 CollectorPolicy *_collector_policy;
78
79 // See the discussion below, in the specification of the reader function
80 // for this variable.
81 int _strong_roots_parity;
82
83 // If we're doing parallel GC, use this gang of threads.
84 WorkGang* _workers;
85
86 // Number of parallel threads currently working on GC tasks.
87 // O indicates use sequential code; 1 means use parallel code even with
88 // only one thread, for performance testing purposes.
89 int _n_par_threads;
90
91 // Full initialization is done in a concrete subtype's "initialize"
92 // function.
93 SharedHeap(CollectorPolicy* policy_);
94
95 // Returns true if the calling thread holds the heap lock,
96 // or the calling thread is a par gc thread and the heap_lock is held
97 // by the vm thread doing a gc operation.
98 bool heap_lock_held_for_gc();
99 // True if the heap_lock is held by the a non-gc thread invoking a gc
100 // operation.
101 bool _thread_holds_heap_lock_for_gc;
102
103 public:
104 static SharedHeap* heap() { return _sh; }
105
106 CollectorPolicy *collector_policy() const { return _collector_policy; }
107
108 void set_barrier_set(BarrierSet* bs);
109
110 // Does operations required after initialization has been done.
111 virtual void post_initialize();
112
113 // Initialization of ("weak") reference processing support
114 virtual void ref_processing_init();
115
116 void set_perm(PermGen* perm_gen) { _perm_gen = perm_gen; }
117
118 // This function returns the "GenRemSet" object that allows us to scan
119 // generations; at least the perm gen, possibly more in a fully
120 // generational heap.
121 GenRemSet* rem_set() { return _rem_set; }
122
123 // These function return the "permanent" generation, in which
124 // reflective objects are allocated and stored. Two versions, the second
125 // of which returns the view of the perm gen as a generation.
126 PermGen* perm() const { return _perm_gen; }
127 Generation* perm_gen() const { return _perm_gen->as_gen(); }
128
129 // Iteration functions.
130 void oop_iterate(OopClosure* cl) = 0;
131
132 // Same as above, restricted to a memory region.
133 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
134
135 // Iterate over all objects allocated since the last collection, calling
136 // "cl->do_object" on each. The heap must have been initialized properly
137 // to support this function, or else this call will fail.
138 virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0;
139
140 // Iterate over all spaces in use in the heap, in an undefined order.
141 virtual void space_iterate(SpaceClosure* cl) = 0;
142
143 // A SharedHeap will contain some number of spaces. This finds the
144 // space whose reserved area contains the given address, or else returns
145 // NULL.
146 virtual Space* space_containing(const void* addr) const = 0;
147
148 bool no_gc_in_progress() { return !is_gc_active(); }
149
150 // Some collectors will perform "process_strong_roots" in parallel.
151 // Such a call will involve claiming some fine-grained tasks, such as
152 // scanning of threads. To make this process simpler, we provide the
153 // "strong_roots_parity()" method. Collectors that start parallel tasks
154 // whose threads invoke "process_strong_roots" must
155 // call "change_strong_roots_parity" in sequential code starting such a
156 // task. (This also means that a parallel thread may only call
157 // process_strong_roots once.)
158 //
159 // For calls to process_strong_roots by sequential code, the parity is
160 // updated automatically.
161 //
162 // The idea is that objects representing fine-grained tasks, such as
163 // threads, will contain a "parity" field. A task will is claimed in the
164 // current "process_strong_roots" call only if its parity field is the
165 // same as the "strong_roots_parity"; task claiming is accomplished by
166 // updating the parity field to the strong_roots_parity with a CAS.
167 //
168 // If the client meats this spec, then strong_roots_parity() will have
169 // the following properties:
170 // a) to return a different value than was returned before the last
171 // call to change_strong_roots_parity, and
172 // c) to never return a distinguished value (zero) with which such
173 // task-claiming variables may be initialized, to indicate "never
174 // claimed".
175 private:
176 void change_strong_roots_parity();
177 public:
178 int strong_roots_parity() { return _strong_roots_parity; }
179
180 // Call these in sequential code around process_strong_roots.
181 // strong_roots_prologue calls change_strong_roots_parity, if
182 // parallel tasks are enabled.
183 class StrongRootsScope : public MarkingCodeBlobClosure::MarkScope {
184 public:
185 StrongRootsScope(SharedHeap* outer, bool activate = true);
186 ~StrongRootsScope();
187 };
188 friend class StrongRootsScope;
189
190 enum ScanningOption {
191 SO_None = 0x0,
192 SO_AllClasses = 0x1,
193 SO_SystemClasses = 0x2,
194 SO_Symbols = 0x4,
195 SO_Strings = 0x8,
196 SO_CodeCache = 0x10
197 };
198
199 WorkGang* workers() const { return _workers; }
200
201 // Sets the number of parallel threads that will be doing tasks
202 // (such as process strong roots) subsequently.
203 virtual void set_par_threads(int t);
204
205 // Number of threads currently working on GC tasks.
206 int n_par_threads() { return _n_par_threads; }
207
208 // Invoke the "do_oop" method the closure "roots" on all root locations.
209 // If "collecting_perm_gen" is false, then roots that may only contain
210 // references to permGen objects are not scanned. If true, the
211 // "perm_gen" closure is applied to all older-to-younger refs in the
212 // permanent generation. The "so" argument determines which of roots
213 // the closure is applied to:
214 // "SO_None" does none;
215 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
216 // "SO_SystemClasses" to all the "system" classes and loaders;
217 // "SO_Symbols" applies the closure to all entries in SymbolsTable;
218 // "SO_Strings" applies the closure to all entries in StringTable;
219 // "SO_CodeCache" applies the closure to all elements of the CodeCache.
220 void process_strong_roots(bool activate_scope,
221 bool collecting_perm_gen,
222 ScanningOption so,
223 OopClosure* roots,
224 CodeBlobClosure* code_roots,
225 OopsInGenClosure* perm_blk);
226
227 // Apply "blk" to all the weak roots of the system. These include
228 // JNI weak roots, the code cache, system dictionary, symbol table,
229 // string table.
230 void process_weak_roots(OopClosure* root_closure,
231 CodeBlobClosure* code_roots,
232 OopClosure* non_root_closure);
233
234 // The functions below are helper functions that a subclass of
235 // "SharedHeap" can use in the implementation of its virtual
236 // functions.
237
238 public:
239
240 // Do anything common to GC's.
241 virtual void gc_prologue(bool full) = 0;
242 virtual void gc_epilogue(bool full) = 0;
243
244 //
245 // New methods from CollectedHeap
246 //
247
248 size_t permanent_capacity() const {
249 assert(perm_gen(), "NULL perm gen");
250 return perm_gen()->capacity();
251 }
252
253 size_t permanent_used() const {
254 assert(perm_gen(), "NULL perm gen");
255 return perm_gen()->used();
256 }
257
258 bool is_in_permanent(const void *p) const {
259 assert(perm_gen(), "NULL perm gen");
260 return perm_gen()->is_in_reserved(p);
261 }
262
263 // Different from is_in_permanent in that is_in_permanent
264 // only checks if p is in the reserved area of the heap
265 // and this checks to see if it in the commited area.
266 // This is typically used by things like the forte stackwalker
267 // during verification of suspicious frame values.
268 bool is_permanent(const void *p) const {
269 assert(perm_gen(), "NULL perm gen");
270 return perm_gen()->is_in(p);
271 }
272
273 HeapWord* permanent_mem_allocate(size_t size) {
274 assert(perm_gen(), "NULL perm gen");
275 return _perm_gen->mem_allocate(size);
276 }
277
278 void permanent_oop_iterate(OopClosure* cl) {
279 assert(perm_gen(), "NULL perm gen");
280 _perm_gen->oop_iterate(cl);
281 }
282
283 void permanent_object_iterate(ObjectClosure* cl) {
284 assert(perm_gen(), "NULL perm gen");
285 _perm_gen->object_iterate(cl);
286 }
287
288 // Some utilities.
289 void print_size_transition(outputStream* out,
290 size_t bytes_before,
291 size_t bytes_after,
292 size_t capacity);
293 };
294
295 #endif // SHARE_VM_MEMORY_SHAREDHEAP_HPP