1 #ifdef USE_PRAGMA_IDENT_HDR 2 #pragma ident "@(#)sharedHeap.hpp 1.56 07/05/05 17:05:55 JVM" 3 #endif 4 /* 5 * Copyright 2000-2006 Sun Microsystems, Inc. All Rights Reserved. 6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 7 * 8 * This code is free software; you can redistribute it and/or modify it 9 * under the terms of the GNU General Public License version 2 only, as 10 * published by the Free Software Foundation. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 23 * CA 95054 USA or visit www.sun.com if you need additional information or 24 * have any questions. 25 * 26 */ 27 28 // A "SharedHeap" is an implementation of a java heap for HotSpot. This 29 // is an abstract class: there may be many different kinds of heaps. This 30 // class defines the functions that a heap must implement, and contains 31 // infrastructure common to all heaps. 32 33 class PermGen; 34 class Generation; 35 class BarrierSet; 36 class GenRemSet; 37 class Space; 38 class SpaceClosure; 39 class OopClosure; 40 class OopsInGenClosure; 41 class ObjectClosure; 42 class SubTasksDone; 43 class WorkGang; 44 class CollectorPolicy; 45 class KlassHandle; 46 47 class SharedHeap : public CollectedHeap { 48 friend class VMStructs; 49 50 private: 51 // For claiming strong_roots tasks. 52 SubTasksDone* _process_strong_tasks; 53 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; 59 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; 64 65 // and the Gen Remembered Set, at least one good enough to scan the perm 66 // gen. 67 GenRemSet* _rem_set; 68 69 // A gc policy, controls global gc resource issues 70 CollectorPolicy *_collector_policy; 71 72 // See the discussion below, in the specification of the reader function 73 // for this variable. 74 int _strong_roots_parity; 75 76 // If we're doing parallel GC, use this gang of threads. 77 WorkGang* _workers; 78 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; 83 84 // Full initialization is done in a concrete subtype's "initialize" 85 // function. 86 SharedHeap(CollectorPolicy* policy_); 87 88 public: 89 static SharedHeap* heap() { return _sh; } 90 91 CollectorPolicy *collector_policy() const { return _collector_policy; } 92 93 void set_barrier_set(BarrierSet* bs); 94 95 // Does operations required after initialization has been done. 96 virtual void post_initialize(); 97 98 // Initialization of ("weak") reference processing support 99 virtual void ref_processing_init(); 100 101 void set_perm(PermGen* perm_gen) { _perm_gen = perm_gen; } 102 103 // A helper function that fills an allocated-but-not-yet-initialized 104 // region with a garbage object. 105 static void fill_region_with_object(MemRegion mr); 106 107 // Minimum garbage fill object size 108 static size_t min_fill_size() { return (size_t)align_object_size(oopDesc::header_size()); } 109 static size_t min_fill_size_in_bytes() { return min_fill_size() * HeapWordSize; } 110 111 // This function returns the "GenRemSet" object that allows us to scan 112 // generations; at least the perm gen, possibly more in a fully 113 // generational heap. 114 GenRemSet* rem_set() { return _rem_set; } 115 116 // These function return the "permanent" generation, in which 117 // reflective objects are allocated and stored. Two versions, the second 118 // of which returns the view of the perm gen as a generation. 119 PermGen* perm() const { return _perm_gen; } 120 Generation* perm_gen() const { return _perm_gen->as_gen(); } 121 122 // Iteration functions. 123 void oop_iterate(OopClosure* cl) = 0; 124 125 // Same as above, restricted to a memory region. 126 virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0; 127 128 // Iterate over all objects allocated since the last collection, calling 129 // "cl->do_object" on each. The heap must have been initialized properly 130 // to support this function, or else this call will fail. 131 virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0; 132 133 // Iterate over all spaces in use in the heap, in an undefined order. 134 virtual void space_iterate(SpaceClosure* cl) = 0; 135 136 // A SharedHeap will contain some number of spaces. This finds the 137 // space whose reserved area contains the given address, or else returns 138 // NULL. 139 virtual Space* space_containing(const void* addr) const = 0; 140 141 bool no_gc_in_progress() { return !is_gc_active(); } 142 143 // Some collectors will perform "process_strong_roots" in parallel. 144 // Such a call will involve claiming some fine-grained tasks, such as 145 // scanning of threads. To make this process simpler, we provide the 146 // "strong_roots_parity()" method. Collectors that start parallel tasks 147 // whose threads invoke "process_strong_roots" must 148 // call "change_strong_roots_parity" in sequential code starting such a 149 // task. (This also means that a parallel thread may only call 150 // process_strong_roots once.) 151 // 152 // For calls to process_strong_roots by sequential code, the parity is 153 // updated automatically. 154 // 155 // The idea is that objects representing fine-grained tasks, such as 156 // threads, will contain a "parity" field. A task will is claimed in the 157 // current "process_strong_roots" call only if its parity field is the 158 // same as the "strong_roots_parity"; task claiming is accomplished by 159 // updating the parity field to the strong_roots_parity with a CAS. 160 // 161 // If the client meats this spec, then strong_roots_parity() will have 162 // the following properties: 163 // a) to return a different value than was returned before the last 164 // call to change_strong_roots_parity, and 165 // c) to never return a distinguished value (zero) with which such 166 // task-claiming variables may be initialized, to indicate "never 167 // claimed". 168 void change_strong_roots_parity(); 169 int strong_roots_parity() { return _strong_roots_parity; } 170 171 enum ScanningOption { 172 SO_None = 0x0, 173 SO_AllClasses = 0x1, 174 SO_SystemClasses = 0x2, 175 SO_Symbols = 0x4, 176 SO_Strings = 0x8, 177 SO_CodeCache = 0x10 178 }; 179 180 WorkGang* workers() const { return _workers; } 181 182 // Sets the number of parallel threads that will be doing tasks 183 // (such as process strong roots) subsequently. 184 virtual void set_par_threads(int t); 185 186 // Number of threads currently working on GC tasks. 187 int n_par_threads() { return _n_par_threads; } 188 189 // Invoke the "do_oop" method the closure "roots" on all root locations. 190 // If "collecting_perm_gen" is false, then roots that may only contain 191 // references to permGen objects are not scanned. If true, the 192 // "perm_gen" closure is applied to all older-to-younger refs in the 193 // permanent generation. The "so" argument determines which of roots 194 // the closure is applied to: 195 // "SO_None" does none; 196 // "SO_AllClasses" applies the closure to all entries in the SystemDictionary; 197 // "SO_SystemClasses" to all the "system" classes and loaders; 198 // "SO_Symbols" applies the closure to all entries in SymbolsTable; 199 // "SO_Strings" applies the closure to all entries in StringTable; 200 // "SO_CodeCache" applies the closure to all elements of the CodeCache. 201 void process_strong_roots(bool collecting_perm_gen, 202 ScanningOption so, 203 OopClosure* roots, 204 OopsInGenClosure* perm_blk); 205 206 // Apply "blk" to all the weak roots of the system. These include 207 // JNI weak roots, the code cache, system dictionary, symbol table, 208 // string table. 209 void process_weak_roots(OopClosure* root_closure, 210 OopClosure* non_root_closure); 211 212 213 // Like CollectedHeap::collect, but assume that the caller holds the Heap_lock. 214 virtual void collect_locked(GCCause::Cause cause) = 0; 215 216 // The functions below are helper functions that a subclass of 217 // "SharedHeap" can use in the implementation of its virtual 218 // functions. 219 220 protected: 221 222 // Do anything common to GC's. 223 virtual void gc_prologue(bool full) = 0; 224 virtual void gc_epilogue(bool full) = 0; 225 226 public: 227 // 228 // New methods from CollectedHeap 229 // 230 231 size_t permanent_capacity() const { 232 assert(perm_gen(), "NULL perm gen"); 233 return perm_gen()->capacity(); 234 } 235 236 size_t permanent_used() const { 237 assert(perm_gen(), "NULL perm gen"); 238 return perm_gen()->used(); 239 } 240 241 bool is_in_permanent(const void *p) const { 242 assert(perm_gen(), "NULL perm gen"); 243 return perm_gen()->is_in_reserved(p); 244 } 245 246 // Different from is_in_permanent in that is_in_permanent 247 // only checks if p is in the reserved area of the heap 248 // and this checks to see if it in the commited area. 249 // This is typically used by things like the forte stackwalker 250 // during verification of suspicious frame values. 251 bool is_permanent(const void *p) const { 252 assert(perm_gen(), "NULL perm gen"); 253 return perm_gen()->is_in(p); 254 } 255 256 HeapWord* permanent_mem_allocate(size_t size) { 257 assert(perm_gen(), "NULL perm gen"); 258 return _perm_gen->mem_allocate(size); 259 } 260 261 void permanent_oop_iterate(OopClosure* cl) { 262 assert(perm_gen(), "NULL perm gen"); 263 _perm_gen->oop_iterate(cl); 264 } 265 266 void permanent_object_iterate(ObjectClosure* cl) { 267 assert(perm_gen(), "NULL perm gen"); 268 _perm_gen->object_iterate(cl); 269 } 270 271 // Some utilities. 272 void print_size_transition(size_t bytes_before, 273 size_t bytes_after, 274 size_t capacity); 275 }; 276 277