Thu, 12 Jun 2008 13:50:55 -0700
Merge
1 /*
2 * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 // A "SharedHeap" is an implementation of a java heap for HotSpot. This
26 // is an abstract class: there may be many different kinds of heaps. This
27 // class defines the functions that a heap must implement, and contains
28 // infrastructure common to all heaps.
30 class PermGen;
31 class Generation;
32 class BarrierSet;
33 class GenRemSet;
34 class Space;
35 class SpaceClosure;
36 class OopClosure;
37 class OopsInGenClosure;
38 class ObjectClosure;
39 class SubTasksDone;
40 class WorkGang;
41 class CollectorPolicy;
42 class KlassHandle;
44 class SharedHeap : public CollectedHeap {
45 friend class VMStructs;
47 friend class VM_GC_Operation;
48 friend class VM_CGC_Operation;
50 private:
51 // For claiming strong_roots tasks.
52 SubTasksDone* _process_strong_tasks;
54 protected:
55 // There should be only a single instance of "SharedHeap" in a program.
56 // This is enforced with the protected constructor below, which will also
57 // set the static pointer "_sh" to that instance.
58 static SharedHeap* _sh;
60 // All heaps contain a "permanent generation." This is some ways
61 // similar to a generation in a generational system, in other ways not.
62 // See the "PermGen" class.
63 PermGen* _perm_gen;
65 // and the Gen Remembered Set, at least one good enough to scan the perm
66 // gen.
67 GenRemSet* _rem_set;
69 // A gc policy, controls global gc resource issues
70 CollectorPolicy *_collector_policy;
72 // See the discussion below, in the specification of the reader function
73 // for this variable.
74 int _strong_roots_parity;
76 // If we're doing parallel GC, use this gang of threads.
77 WorkGang* _workers;
79 // Number of parallel threads currently working on GC tasks.
80 // O indicates use sequential code; 1 means use parallel code even with
81 // only one thread, for performance testing purposes.
82 int _n_par_threads;
84 // Full initialization is done in a concrete subtype's "initialize"
85 // function.
86 SharedHeap(CollectorPolicy* policy_);
88 // Returns true if the calling thread holds the heap lock,
89 // or the calling thread is a par gc thread and the heap_lock is held
90 // by the vm thread doing a gc operation.
91 bool heap_lock_held_for_gc();
92 // True if the heap_lock is held by the a non-gc thread invoking a gc
93 // operation.
94 bool _thread_holds_heap_lock_for_gc;
96 public:
97 static SharedHeap* heap() { return _sh; }
99 CollectorPolicy *collector_policy() const { return _collector_policy; }
101 void set_barrier_set(BarrierSet* bs);
103 // Does operations required after initialization has been done.
104 virtual void post_initialize();
106 // Initialization of ("weak") reference processing support
107 virtual void ref_processing_init();
109 void set_perm(PermGen* perm_gen) { _perm_gen = perm_gen; }
111 // A helper function that fills a region of the heap with
112 // with a single object.
113 static void fill_region_with_object(MemRegion mr);
115 // Minimum garbage fill object size
116 static size_t min_fill_size() { return (size_t)align_object_size(oopDesc::header_size()); }
117 static size_t min_fill_size_in_bytes() { return min_fill_size() * HeapWordSize; }
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; }
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(); }
130 // Iteration functions.
131 void oop_iterate(OopClosure* cl) = 0;
133 // Same as above, restricted to a memory region.
134 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0;
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;
141 // Iterate over all spaces in use in the heap, in an undefined order.
142 virtual void space_iterate(SpaceClosure* cl) = 0;
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;
149 bool no_gc_in_progress() { return !is_gc_active(); }
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 void change_strong_roots_parity();
177 int strong_roots_parity() { return _strong_roots_parity; }
179 enum ScanningOption {
180 SO_None = 0x0,
181 SO_AllClasses = 0x1,
182 SO_SystemClasses = 0x2,
183 SO_Symbols = 0x4,
184 SO_Strings = 0x8,
185 SO_CodeCache = 0x10
186 };
188 WorkGang* workers() const { return _workers; }
190 // Sets the number of parallel threads that will be doing tasks
191 // (such as process strong roots) subsequently.
192 virtual void set_par_threads(int t);
194 // Number of threads currently working on GC tasks.
195 int n_par_threads() { return _n_par_threads; }
197 // Invoke the "do_oop" method the closure "roots" on all root locations.
198 // If "collecting_perm_gen" is false, then roots that may only contain
199 // references to permGen objects are not scanned. If true, the
200 // "perm_gen" closure is applied to all older-to-younger refs in the
201 // permanent generation. The "so" argument determines which of roots
202 // the closure is applied to:
203 // "SO_None" does none;
204 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
205 // "SO_SystemClasses" to all the "system" classes and loaders;
206 // "SO_Symbols" applies the closure to all entries in SymbolsTable;
207 // "SO_Strings" applies the closure to all entries in StringTable;
208 // "SO_CodeCache" applies the closure to all elements of the CodeCache.
209 void process_strong_roots(bool collecting_perm_gen,
210 ScanningOption so,
211 OopClosure* roots,
212 OopsInGenClosure* perm_blk);
214 // Apply "blk" to all the weak roots of the system. These include
215 // JNI weak roots, the code cache, system dictionary, symbol table,
216 // string table.
217 void process_weak_roots(OopClosure* root_closure,
218 OopClosure* non_root_closure);
221 // Like CollectedHeap::collect, but assume that the caller holds the Heap_lock.
222 virtual void collect_locked(GCCause::Cause cause) = 0;
224 // The functions below are helper functions that a subclass of
225 // "SharedHeap" can use in the implementation of its virtual
226 // functions.
228 public:
230 // Do anything common to GC's.
231 virtual void gc_prologue(bool full) = 0;
232 virtual void gc_epilogue(bool full) = 0;
234 //
235 // New methods from CollectedHeap
236 //
238 size_t permanent_capacity() const {
239 assert(perm_gen(), "NULL perm gen");
240 return perm_gen()->capacity();
241 }
243 size_t permanent_used() const {
244 assert(perm_gen(), "NULL perm gen");
245 return perm_gen()->used();
246 }
248 bool is_in_permanent(const void *p) const {
249 assert(perm_gen(), "NULL perm gen");
250 return perm_gen()->is_in_reserved(p);
251 }
253 // Different from is_in_permanent in that is_in_permanent
254 // only checks if p is in the reserved area of the heap
255 // and this checks to see if it in the commited area.
256 // This is typically used by things like the forte stackwalker
257 // during verification of suspicious frame values.
258 bool is_permanent(const void *p) const {
259 assert(perm_gen(), "NULL perm gen");
260 return perm_gen()->is_in(p);
261 }
263 HeapWord* permanent_mem_allocate(size_t size) {
264 assert(perm_gen(), "NULL perm gen");
265 return _perm_gen->mem_allocate(size);
266 }
268 void permanent_oop_iterate(OopClosure* cl) {
269 assert(perm_gen(), "NULL perm gen");
270 _perm_gen->oop_iterate(cl);
271 }
273 void permanent_object_iterate(ObjectClosure* cl) {
274 assert(perm_gen(), "NULL perm gen");
275 _perm_gen->object_iterate(cl);
276 }
278 // Some utilities.
279 void print_size_transition(outputStream* out,
280 size_t bytes_before,
281 size_t bytes_after,
282 size_t capacity);
283 };