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