1 /* 2 * Copyright (c) 2003, 2008, 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 "incls/_precompiled.incl" 26 #include "incls/_compactingPermGenGen.cpp.incl" 27 28 29 // An ObjectClosure helper: Recursively adjust all pointers in an object 30 // and all objects by referenced it. Clear marks on objects in order to 31 // prevent visiting any object twice. This helper is used when the 32 // RedefineClasses() API has been called. 33 34 class AdjustSharedObjectClosure : public ObjectClosure { 35 public: 36 void do_object(oop obj) { 37 if (obj->is_shared_readwrite()) { 38 if (obj->mark()->is_marked()) { 39 obj->init_mark(); // Don't revisit this object. 40 obj->adjust_pointers(); // Adjust this object's references. 41 } 42 } 43 } 44 }; 45 46 47 // An OopClosure helper: Recursively adjust all pointers in an object 48 // and all objects by referenced it. Clear marks on objects in order 49 // to prevent visiting any object twice. 50 51 class RecursiveAdjustSharedObjectClosure : public OopClosure { 52 protected: 53 template <class T> inline void do_oop_work(T* p) { 54 oop obj = oopDesc::load_decode_heap_oop_not_null(p); 55 if (obj->is_shared_readwrite()) { 56 if (obj->mark()->is_marked()) { 57 obj->init_mark(); // Don't revisit this object. 58 obj->oop_iterate(this); // Recurse - adjust objects referenced. 59 obj->adjust_pointers(); // Adjust this object's references. 60 61 // Special case: if a class has a read-only constant pool, 62 // then the read-write objects referenced by the pool must 63 // have their marks reset. 64 65 if (obj->klass() == Universe::instanceKlassKlassObj()) { 66 instanceKlass* ik = instanceKlass::cast((klassOop)obj); 67 constantPoolOop cp = ik->constants(); 68 if (cp->is_shared_readonly()) { 69 cp->oop_iterate(this); 70 } 71 } 72 } 73 } 74 } 75 public: 76 virtual void do_oop(oop* p) { RecursiveAdjustSharedObjectClosure::do_oop_work(p); } 77 virtual void do_oop(narrowOop* p) { RecursiveAdjustSharedObjectClosure::do_oop_work(p); } 78 }; 79 80 81 // We need to go through all placeholders in the system dictionary and 82 // try to resolve them into shared classes. Other threads might be in 83 // the process of loading a shared class and have strong roots on 84 // their stack to the class without having added the class to the 85 // dictionary yet. This means the class will be marked during phase 1 86 // but will not be unmarked during the application of the 87 // RecursiveAdjustSharedObjectClosure to the SystemDictionary. Note 88 // that we must not call find_shared_class with non-read-only symbols 89 // as doing so can cause hash codes to be computed, destroying 90 // forwarding pointers. 91 class TraversePlaceholdersClosure : public OopClosure { 92 protected: 93 template <class T> inline void do_oop_work(T* p) { 94 oop obj = oopDesc::load_decode_heap_oop_not_null(p); 95 if (obj->klass() == Universe::symbolKlassObj() && 96 obj->is_shared_readonly()) { 97 symbolHandle sym((symbolOop) obj); 98 oop k = SystemDictionary::find_shared_class(sym); 99 if (k != NULL) { 100 RecursiveAdjustSharedObjectClosure clo; 101 clo.do_oop(&k); 102 } 103 } 104 } 105 public: 106 virtual void do_oop(oop* p) { TraversePlaceholdersClosure::do_oop_work(p); } 107 virtual void do_oop(narrowOop* p) { TraversePlaceholdersClosure::do_oop_work(p); } 108 109 }; 110 111 112 void CompactingPermGenGen::initialize_performance_counters() { 113 114 const char* gen_name = "perm"; 115 116 // Generation Counters - generation 2, 1 subspace 117 _gen_counters = new GenerationCounters(gen_name, 2, 1, &_virtual_space); 118 119 _space_counters = new CSpaceCounters(gen_name, 0, 120 _virtual_space.reserved_size(), 121 _the_space, _gen_counters); 122 } 123 124 void CompactingPermGenGen::update_counters() { 125 if (UsePerfData) { 126 _space_counters->update_all(); 127 _gen_counters->update_all(); 128 } 129 } 130 131 132 CompactingPermGenGen::CompactingPermGenGen(ReservedSpace rs, 133 ReservedSpace shared_rs, 134 size_t initial_byte_size, 135 int level, GenRemSet* remset, 136 ContiguousSpace* space, 137 PermanentGenerationSpec* spec_) : 138 OneContigSpaceCardGeneration(rs, initial_byte_size, MinPermHeapExpansion, 139 level, remset, space) { 140 141 set_spec(spec_); 142 if (!UseSharedSpaces && !DumpSharedSpaces) { 143 spec()->disable_sharing(); 144 } 145 146 // Break virtual space into address ranges for all spaces. 147 148 if (spec()->enable_shared_spaces()) { 149 shared_end = (HeapWord*)(shared_rs.base() + shared_rs.size()); 150 misccode_end = shared_end; 151 misccode_bottom = misccode_end - heap_word_size(spec()->misc_code_size()); 152 miscdata_end = misccode_bottom; 153 miscdata_bottom = miscdata_end - heap_word_size(spec()->misc_data_size()); 154 readwrite_end = miscdata_bottom; 155 readwrite_bottom = 156 readwrite_end - heap_word_size(spec()->read_write_size()); 157 readonly_end = readwrite_bottom; 158 readonly_bottom = 159 readonly_end - heap_word_size(spec()->read_only_size()); 160 shared_bottom = readonly_bottom; 161 unshared_end = shared_bottom; 162 assert((char*)shared_bottom == shared_rs.base(), "shared space mismatch"); 163 } else { 164 shared_end = (HeapWord*)(rs.base() + rs.size()); 165 misccode_end = shared_end; 166 misccode_bottom = shared_end; 167 miscdata_end = shared_end; 168 miscdata_bottom = shared_end; 169 readwrite_end = shared_end; 170 readwrite_bottom = shared_end; 171 readonly_end = shared_end; 172 readonly_bottom = shared_end; 173 shared_bottom = shared_end; 174 unshared_end = shared_bottom; 175 } 176 unshared_bottom = (HeapWord*) rs.base(); 177 178 // Verify shared and unshared spaces adjacent. 179 assert((char*)shared_bottom == rs.base()+rs.size(), "shared space mismatch"); 180 assert(unshared_end > unshared_bottom, "shared space mismatch"); 181 182 // Split reserved memory into pieces. 183 184 ReservedSpace ro_rs = shared_rs.first_part(spec()->read_only_size(), 185 UseSharedSpaces); 186 ReservedSpace tmp_rs1 = shared_rs.last_part(spec()->read_only_size()); 187 ReservedSpace rw_rs = tmp_rs1.first_part(spec()->read_write_size(), 188 UseSharedSpaces); 189 ReservedSpace tmp_rs2 = tmp_rs1.last_part(spec()->read_write_size()); 190 ReservedSpace md_rs = tmp_rs2.first_part(spec()->misc_data_size(), 191 UseSharedSpaces); 192 ReservedSpace mc_rs = tmp_rs2.last_part(spec()->misc_data_size()); 193 194 _shared_space_size = spec()->read_only_size() 195 + spec()->read_write_size() 196 + spec()->misc_data_size() 197 + spec()->misc_code_size(); 198 199 // Allocate the unshared (default) space. 200 _the_space = new ContigPermSpace(_bts, 201 MemRegion(unshared_bottom, heap_word_size(initial_byte_size))); 202 if (_the_space == NULL) 203 vm_exit_during_initialization("Could not allocate an unshared" 204 " CompactingPermGen Space"); 205 206 // Allocate shared spaces 207 if (spec()->enable_shared_spaces()) { 208 209 // If mapping a shared file, the space is not committed, don't 210 // mangle. 211 NOT_PRODUCT(bool old_ZapUnusedHeapArea = ZapUnusedHeapArea;) 212 NOT_PRODUCT(if (UseSharedSpaces) ZapUnusedHeapArea = false;) 213 214 // Commit the memory behind the shared spaces if dumping (not 215 // mapping). 216 if (DumpSharedSpaces) { 217 _ro_vs.initialize(ro_rs, spec()->read_only_size()); 218 _rw_vs.initialize(rw_rs, spec()->read_write_size()); 219 _md_vs.initialize(md_rs, spec()->misc_data_size()); 220 _mc_vs.initialize(mc_rs, spec()->misc_code_size()); 221 } 222 223 // Allocate the shared spaces. 224 _ro_bts = new BlockOffsetSharedArray( 225 MemRegion(readonly_bottom, 226 heap_word_size(spec()->read_only_size())), 227 heap_word_size(spec()->read_only_size())); 228 _ro_space = new OffsetTableContigSpace(_ro_bts, 229 MemRegion(readonly_bottom, readonly_end)); 230 _rw_bts = new BlockOffsetSharedArray( 231 MemRegion(readwrite_bottom, 232 heap_word_size(spec()->read_write_size())), 233 heap_word_size(spec()->read_write_size())); 234 _rw_space = new OffsetTableContigSpace(_rw_bts, 235 MemRegion(readwrite_bottom, readwrite_end)); 236 237 // Restore mangling flag. 238 NOT_PRODUCT(ZapUnusedHeapArea = old_ZapUnusedHeapArea;) 239 240 if (_ro_space == NULL || _rw_space == NULL) 241 vm_exit_during_initialization("Could not allocate a shared space"); 242 243 // Cover both shared spaces entirely with cards. 244 _rs->resize_covered_region(MemRegion(readonly_bottom, readwrite_end)); 245 246 if (UseSharedSpaces) { 247 248 // Map in the regions in the shared file. 249 FileMapInfo* mapinfo = FileMapInfo::current_info(); 250 size_t image_alignment = mapinfo->alignment(); 251 CollectedHeap* ch = Universe::heap(); 252 if ((!mapinfo->map_space(ro, ro_rs, _ro_space)) || 253 (!mapinfo->map_space(rw, rw_rs, _rw_space)) || 254 (!mapinfo->map_space(md, md_rs, NULL)) || 255 (!mapinfo->map_space(mc, mc_rs, NULL)) || 256 // check the alignment constraints 257 (ch == NULL || ch->kind() != CollectedHeap::GenCollectedHeap || 258 image_alignment != 259 ((GenCollectedHeap*)ch)->gen_policy()->max_alignment())) { 260 // Base addresses didn't match; skip sharing, but continue 261 shared_rs.release(); 262 spec()->disable_sharing(); 263 // If -Xshare:on is specified, print out the error message and exit VM, 264 // otherwise, set UseSharedSpaces to false and continue. 265 if (RequireSharedSpaces) { 266 vm_exit_during_initialization("Unable to use shared archive.", NULL); 267 } else { 268 FLAG_SET_DEFAULT(UseSharedSpaces, false); 269 } 270 271 // Note: freeing the block offset array objects does not 272 // currently free up the underlying storage. 273 delete _ro_bts; 274 _ro_bts = NULL; 275 delete _ro_space; 276 _ro_space = NULL; 277 delete _rw_bts; 278 _rw_bts = NULL; 279 delete _rw_space; 280 _rw_space = NULL; 281 shared_end = (HeapWord*)(rs.base() + rs.size()); 282 _rs->resize_covered_region(MemRegion(shared_bottom, shared_bottom)); 283 } 284 } 285 286 // Reserved region includes shared spaces for oop.is_in_reserved(). 287 _reserved.set_end(shared_end); 288 289 } else { 290 _ro_space = NULL; 291 _rw_space = NULL; 292 } 293 } 294 295 296 // Do a complete scan of the shared read write space to catch all 297 // objects which contain references to any younger generation. Forward 298 // the pointers. Avoid space_iterate, as actually visiting all the 299 // objects in the space will page in more objects than we need. 300 // Instead, use the system dictionary as strong roots into the read 301 // write space. 302 // 303 // If a RedefineClasses() call has been made, then we have to iterate 304 // over the entire shared read-write space in order to find all the 305 // objects that need to be forwarded. For example, it is possible for 306 // an nmethod to be found and marked in GC phase-1 only for the nmethod 307 // to be freed by the time we reach GC phase-3. The underlying method 308 // is still marked, but we can't (easily) find it in GC phase-3 so we 309 // blow up in GC phase-4. With RedefineClasses() we want replaced code 310 // (EMCP or obsolete) to go away (i.e., be collectible) once it is no 311 // longer being executed by any thread so we keep minimal attachments 312 // to the replaced code. However, we can't guarantee when those EMCP 313 // or obsolete methods will be collected so they may still be out there 314 // even after we've severed our minimal attachments. 315 316 void CompactingPermGenGen::pre_adjust_pointers() { 317 if (spec()->enable_shared_spaces()) { 318 if (JvmtiExport::has_redefined_a_class()) { 319 // RedefineClasses() requires a brute force approach 320 AdjustSharedObjectClosure blk; 321 rw_space()->object_iterate(&blk); 322 } else { 323 RecursiveAdjustSharedObjectClosure blk; 324 Universe::oops_do(&blk); 325 StringTable::oops_do(&blk); 326 SystemDictionary::always_strong_classes_do(&blk); 327 TraversePlaceholdersClosure tpc; 328 SystemDictionary::placeholders_do(&tpc); 329 } 330 } 331 } 332 333 334 #ifdef ASSERT 335 class VerifyMarksClearedClosure : public ObjectClosure { 336 public: 337 void do_object(oop obj) { 338 assert(SharedSkipVerify || !obj->mark()->is_marked(), 339 "Shared oop still marked?"); 340 } 341 }; 342 #endif 343 344 345 void CompactingPermGenGen::post_compact() { 346 #ifdef ASSERT 347 if (!SharedSkipVerify && spec()->enable_shared_spaces()) { 348 VerifyMarksClearedClosure blk; 349 rw_space()->object_iterate(&blk); 350 } 351 #endif 352 } 353 354 355 // Do not use in time-critical operations due to the possibility of paging 356 // in otherwise untouched or previously unread portions of the perm gen, 357 // for instance, the shared spaces. NOTE: Because CompactingPermGenGen 358 // derives from OneContigSpaceCardGeneration which is supposed to have a 359 // single space, and does not override its object_iterate() method, 360 // object iteration via that interface does not look at the objects in 361 // the shared spaces when using CDS. This should be fixed; see CR 6897798. 362 void CompactingPermGenGen::space_iterate(SpaceClosure* blk, bool usedOnly) { 363 OneContigSpaceCardGeneration::space_iterate(blk, usedOnly); 364 if (spec()->enable_shared_spaces()) { 365 // Making the rw_space walkable will page in the entire space, and 366 // is to be avoided in the case of time-critical operations. 367 // However, this is required for Verify and heap dump operations. 368 blk->do_space(ro_space()); 369 blk->do_space(rw_space()); 370 } 371 } 372 373 374 void CompactingPermGenGen::print_on(outputStream* st) const { 375 OneContigSpaceCardGeneration::print_on(st); 376 if (spec()->enable_shared_spaces()) { 377 st->print(" ro"); 378 ro_space()->print_on(st); 379 st->print(" rw"); 380 rw_space()->print_on(st); 381 } else { 382 st->print_cr("No shared spaces configured."); 383 } 384 } 385 386 387 // References from the perm gen to the younger generation objects may 388 // occur in static fields in Java classes or in constant pool references 389 // to String objects. 390 391 void CompactingPermGenGen::younger_refs_iterate(OopsInGenClosure* blk) { 392 OneContigSpaceCardGeneration::younger_refs_iterate(blk); 393 if (spec()->enable_shared_spaces()) { 394 blk->set_generation(this); 395 // ro_space has no younger gen refs. 396 _rs->younger_refs_in_space_iterate(rw_space(), blk); 397 blk->reset_generation(); 398 } 399 } 400 401 402 // Shared spaces are addressed in pre_adjust_pointers. 403 void CompactingPermGenGen::adjust_pointers() { 404 the_space()->adjust_pointers(); 405 } 406 407 408 void CompactingPermGenGen::compact() { 409 the_space()->compact(); 410 } 411 412 413 size_t CompactingPermGenGen::contiguous_available() const { 414 // Don't include shared spaces. 415 return OneContigSpaceCardGeneration::contiguous_available() 416 - _shared_space_size; 417 } 418 419 size_t CompactingPermGenGen::max_capacity() const { 420 // Don't include shared spaces. 421 assert(UseSharedSpaces || (_shared_space_size == 0), 422 "If not used, the size of shared spaces should be 0"); 423 return OneContigSpaceCardGeneration::max_capacity() 424 - _shared_space_size; 425 } 426 427 428 // No young generation references, clear this generation's main space's 429 // card table entries. Do NOT clear the card table entries for the 430 // read-only space (always clear) or the read-write space (valuable 431 // information). 432 433 void CompactingPermGenGen::clear_remembered_set() { 434 _rs->clear(MemRegion(the_space()->bottom(), the_space()->end())); 435 } 436 437 438 // Objects in this generation's main space may have moved, invalidate 439 // that space's cards. Do NOT invalidate the card table entries for the 440 // read-only or read-write spaces, as those objects never move. 441 442 void CompactingPermGenGen::invalidate_remembered_set() { 443 _rs->invalidate(used_region()); 444 } 445 446 447 void CompactingPermGenGen::verify(bool allow_dirty) { 448 the_space()->verify(allow_dirty); 449 if (!SharedSkipVerify && spec()->enable_shared_spaces()) { 450 ro_space()->verify(allow_dirty); 451 rw_space()->verify(allow_dirty); 452 } 453 } 454 455 456 HeapWord* CompactingPermGenGen::unshared_bottom; 457 HeapWord* CompactingPermGenGen::unshared_end; 458 HeapWord* CompactingPermGenGen::shared_bottom; 459 HeapWord* CompactingPermGenGen::shared_end; 460 HeapWord* CompactingPermGenGen::readonly_bottom; 461 HeapWord* CompactingPermGenGen::readonly_end; 462 HeapWord* CompactingPermGenGen::readwrite_bottom; 463 HeapWord* CompactingPermGenGen::readwrite_end; 464 HeapWord* CompactingPermGenGen::miscdata_bottom; 465 HeapWord* CompactingPermGenGen::miscdata_end; 466 HeapWord* CompactingPermGenGen::misccode_bottom; 467 HeapWord* CompactingPermGenGen::misccode_end; 468 469 // JVM/TI RedefineClasses() support: 470 bool CompactingPermGenGen::remap_shared_readonly_as_readwrite() { 471 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 472 473 if (UseSharedSpaces) { 474 // remap the shared readonly space to shared readwrite, private 475 FileMapInfo* mapinfo = FileMapInfo::current_info(); 476 if (!mapinfo->remap_shared_readonly_as_readwrite()) { 477 return false; 478 } 479 } 480 return true; 481 } 482 483 void** CompactingPermGenGen::_vtbl_list;