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;