1 /*
   2  * Copyright (c) 2001, 2012, 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 "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "gc_implementation/shared/vmGCOperations.hpp"
  28 #include "gc_interface/collectedHeap.hpp"
  29 #include "gc_interface/collectedHeap.inline.hpp"
  30 #include "oops/oop.inline.hpp"
  31 #include "oops/instanceMirrorKlass.hpp"
  32 #include "runtime/init.hpp"
  33 #include "runtime/thread.inline.hpp"
  34 #include "services/heapDumper.hpp"
  35 
  36 
  37 #ifdef ASSERT
  38 int CollectedHeap::_fire_out_of_memory_count = 0;
  39 #endif
  40 
  41 size_t CollectedHeap::_filler_array_max_size = 0;
  42 
  43 template <>
  44 void EventLogBase<GCMessage>::print(outputStream* st, GCMessage& m) {
  45   st->print_cr("GC heap %s", m.is_before ? "before" : "after");
  46   st->print_raw(m);
  47 }
  48 
  49 void GCHeapLog::log_heap(bool before) {
  50   if (!should_log()) {
  51     return;
  52   }
  53 
  54   double timestamp = fetch_timestamp();
  55   MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);
  56   int index = compute_log_index();
  57   _records[index].thread = NULL; // Its the GC thread so it's not that interesting.
  58   _records[index].timestamp = timestamp;
  59   _records[index].data.is_before = before;
  60   stringStream st(_records[index].data.buffer(), _records[index].data.size());
  61   if (before) {
  62     Universe::print_heap_before_gc(&st, true);
  63   } else {
  64     Universe::print_heap_after_gc(&st, true);
  65   }
  66 }
  67 
  68 // Memory state functions.
  69 
  70 
  71 CollectedHeap::CollectedHeap() : _n_par_threads(0)
  72 
  73 {
  74   const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
  75   const size_t elements_per_word = HeapWordSize / sizeof(jint);
  76   _filler_array_max_size = align_object_size(filler_array_hdr_size() +
  77                                              max_len / elements_per_word);
  78 
  79   _barrier_set = NULL;
  80   _is_gc_active = false;
  81   _total_collections = _total_full_collections = 0;
  82   _gc_cause = _gc_lastcause = GCCause::_no_gc;
  83   NOT_PRODUCT(_promotion_failure_alot_count = 0;)
  84   NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
  85 
  86   if (UsePerfData) {
  87     EXCEPTION_MARK;
  88 
  89     // create the gc cause jvmstat counters
  90     _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
  91                              80, GCCause::to_string(_gc_cause), CHECK);
  92 
  93     _perf_gc_lastcause =
  94                 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
  95                              80, GCCause::to_string(_gc_lastcause), CHECK);
  96   }
  97   _defer_initial_card_mark = false; // strengthened by subclass in pre_initialize() below.
  98   // Create the ring log
  99   if (LogEvents) {
 100     _gc_heap_log = new GCHeapLog();
 101   } else {
 102     _gc_heap_log = NULL;
 103   }
 104 }
 105 
 106 // This interface assumes that it's being called by the
 107 // vm thread. It collects the heap assuming that the
 108 // heap lock is already held and that we are executing in
 109 // the context of the vm thread.
 110 void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
 111   assert(Thread::current()->is_VM_thread(), "Precondition#1");
 112   assert(Heap_lock->is_locked(), "Precondition#2");
 113   GCCauseSetter gcs(this, cause);
 114   switch (cause) {
 115     case GCCause::_heap_inspection:
 116     case GCCause::_heap_dump:
 117     case GCCause::_metadata_GC_threshold : {
 118       HandleMark hm;
 119       do_full_collection(false);        // don't clear all soft refs
 120       break;
 121     }
 122     case GCCause::_last_ditch_collection: {
 123       HandleMark hm;
 124       do_full_collection(true);         // do clear all soft refs
 125       break;
 126     }
 127     default:
 128       ShouldNotReachHere(); // Unexpected use of this function
 129   }
 130 }
 131 MetaWord* CollectedHeap::satisfy_failed_metadata_allocation(
 132                                               ClassLoaderData* loader_data,
 133                                               size_t size, Metaspace::MetadataType mdtype) {
 134   return collector_policy()->satisfy_failed_metadata_allocation(loader_data, size, mdtype);
 135 }
 136 
 137 
 138 void CollectedHeap::pre_initialize() {
 139   // Used for ReduceInitialCardMarks (when COMPILER2 is used);
 140   // otherwise remains unused.
 141 #ifdef COMPILER2
 142   _defer_initial_card_mark =    ReduceInitialCardMarks && can_elide_tlab_store_barriers()
 143                              && (DeferInitialCardMark || card_mark_must_follow_store());
 144 #else
 145   assert(_defer_initial_card_mark == false, "Who would set it?");
 146 #endif
 147 }
 148 
 149 #ifndef PRODUCT
 150 void CollectedHeap::check_for_bad_heap_word_value(HeapWord* addr, size_t size) {
 151   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 152     for (size_t slot = 0; slot < size; slot += 1) {
 153       assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
 154              "Found badHeapWordValue in post-allocation check");
 155     }
 156   }
 157 }
 158 
 159 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {
 160   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 161     for (size_t slot = 0; slot < size; slot += 1) {
 162       assert((*(intptr_t*) (addr + slot)) == ((intptr_t) badHeapWordVal),
 163              "Found non badHeapWordValue in pre-allocation check");
 164     }
 165   }
 166 }
 167 #endif // PRODUCT
 168 
 169 #ifdef ASSERT
 170 void CollectedHeap::check_for_valid_allocation_state() {
 171   Thread *thread = Thread::current();
 172   // How to choose between a pending exception and a potential
 173   // OutOfMemoryError?  Don't allow pending exceptions.
 174   // This is a VM policy failure, so how do we exhaustively test it?
 175   assert(!thread->has_pending_exception(),
 176          "shouldn't be allocating with pending exception");
 177   if (StrictSafepointChecks) {
 178     assert(thread->allow_allocation(),
 179            "Allocation done by thread for which allocation is blocked "
 180            "by No_Allocation_Verifier!");
 181     // Allocation of an oop can always invoke a safepoint,
 182     // hence, the true argument
 183     thread->check_for_valid_safepoint_state(true);
 184   }
 185 }
 186 #endif
 187 
 188 HeapWord* CollectedHeap::allocate_from_tlab_slow(Thread* thread, size_t size) {
 189 
 190   // Retain tlab and allocate object in shared space if
 191   // the amount free in the tlab is too large to discard.
 192   if (thread->tlab().free() > thread->tlab().refill_waste_limit()) {
 193     thread->tlab().record_slow_allocation(size);
 194     return NULL;
 195   }
 196 
 197   // Discard tlab and allocate a new one.
 198   // To minimize fragmentation, the last TLAB may be smaller than the rest.
 199   size_t new_tlab_size = thread->tlab().compute_size(size);
 200 
 201   thread->tlab().clear_before_allocation();
 202 
 203   if (new_tlab_size == 0) {
 204     return NULL;
 205   }
 206 
 207   // Allocate a new TLAB...
 208   HeapWord* obj = Universe::heap()->allocate_new_tlab(new_tlab_size);
 209   if (obj == NULL) {
 210     return NULL;
 211   }
 212   if (ZeroTLAB) {
 213     // ..and clear it.
 214     Copy::zero_to_words(obj, new_tlab_size);
 215   } else {
 216     // ...and zap just allocated object.
 217 #ifdef ASSERT
 218     // Skip mangling the space corresponding to the object header to
 219     // ensure that the returned space is not considered parsable by
 220     // any concurrent GC thread.
 221     size_t hdr_size = oopDesc::header_size();
 222     Copy::fill_to_words(obj + hdr_size, new_tlab_size - hdr_size, badHeapWordVal);
 223 #endif // ASSERT
 224   }
 225   thread->tlab().fill(obj, obj + size, new_tlab_size);
 226   return obj;
 227 }
 228 
 229 void CollectedHeap::flush_deferred_store_barrier(JavaThread* thread) {
 230   MemRegion deferred = thread->deferred_card_mark();
 231   if (!deferred.is_empty()) {
 232     assert(_defer_initial_card_mark, "Otherwise should be empty");
 233     {
 234       // Verify that the storage points to a parsable object in heap
 235       DEBUG_ONLY(oop old_obj = oop(deferred.start());)
 236       assert(is_in(old_obj), "Not in allocated heap");
 237       assert(!can_elide_initializing_store_barrier(old_obj),
 238              "Else should have been filtered in new_store_pre_barrier()");
 239       assert(old_obj->is_oop(true), "Not an oop");
 240       assert(deferred.word_size() == (size_t)(old_obj->size()),
 241              "Mismatch: multiple objects?");
 242     }
 243     BarrierSet* bs = barrier_set();
 244     assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
 245     bs->write_region(deferred);
 246     // "Clear" the deferred_card_mark field
 247     thread->set_deferred_card_mark(MemRegion());
 248   }
 249   assert(thread->deferred_card_mark().is_empty(), "invariant");
 250 }
 251 
 252 // Helper for ReduceInitialCardMarks. For performance,
 253 // compiled code may elide card-marks for initializing stores
 254 // to a newly allocated object along the fast-path. We
 255 // compensate for such elided card-marks as follows:
 256 // (a) Generational, non-concurrent collectors, such as
 257 //     GenCollectedHeap(ParNew,DefNew,Tenured) and
 258 //     ParallelScavengeHeap(ParallelGC, ParallelOldGC)
 259 //     need the card-mark if and only if the region is
 260 //     in the old gen, and do not care if the card-mark
 261 //     succeeds or precedes the initializing stores themselves,
 262 //     so long as the card-mark is completed before the next
 263 //     scavenge. For all these cases, we can do a card mark
 264 //     at the point at which we do a slow path allocation
 265 //     in the old gen, i.e. in this call.
 266 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
 267 //     in addition that the card-mark for an old gen allocated
 268 //     object strictly follow any associated initializing stores.
 269 //     In these cases, the memRegion remembered below is
 270 //     used to card-mark the entire region either just before the next
 271 //     slow-path allocation by this thread or just before the next scavenge or
 272 //     CMS-associated safepoint, whichever of these events happens first.
 273 //     (The implicit assumption is that the object has been fully
 274 //     initialized by this point, a fact that we assert when doing the
 275 //     card-mark.)
 276 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
 277 //     G1 concurrent marking is in progress an SATB (pre-write-)barrier is
 278 //     is used to remember the pre-value of any store. Initializing
 279 //     stores will not need this barrier, so we need not worry about
 280 //     compensating for the missing pre-barrier here. Turning now
 281 //     to the post-barrier, we note that G1 needs a RS update barrier
 282 //     which simply enqueues a (sequence of) dirty cards which may
 283 //     optionally be refined by the concurrent update threads. Note
 284 //     that this barrier need only be applied to a non-young write,
 285 //     but, like in CMS, because of the presence of concurrent refinement
 286 //     (much like CMS' precleaning), must strictly follow the oop-store.
 287 //     Thus, using the same protocol for maintaining the intended
 288 //     invariants turns out, serendepitously, to be the same for both
 289 //     G1 and CMS.
 290 //
 291 // For any future collector, this code should be reexamined with
 292 // that specific collector in mind, and the documentation above suitably
 293 // extended and updated.
 294 oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {
 295   // If a previous card-mark was deferred, flush it now.
 296   flush_deferred_store_barrier(thread);
 297   if (can_elide_initializing_store_barrier(new_obj)) {
 298     // The deferred_card_mark region should be empty
 299     // following the flush above.
 300     assert(thread->deferred_card_mark().is_empty(), "Error");
 301   } else {
 302     MemRegion mr((HeapWord*)new_obj, new_obj->size());
 303     assert(!mr.is_empty(), "Error");
 304     if (_defer_initial_card_mark) {
 305       // Defer the card mark
 306       thread->set_deferred_card_mark(mr);
 307     } else {
 308       // Do the card mark
 309       BarrierSet* bs = barrier_set();
 310       assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
 311       bs->write_region(mr);
 312     }
 313   }
 314   return new_obj;
 315 }
 316 
 317 size_t CollectedHeap::filler_array_hdr_size() {
 318   return size_t(align_object_offset(arrayOopDesc::header_size(T_INT))); // align to Long
 319 }
 320 
 321 size_t CollectedHeap::filler_array_min_size() {
 322   return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
 323 }
 324 
 325 #ifdef ASSERT
 326 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
 327 {
 328   assert(words >= min_fill_size(), "too small to fill");
 329   assert(words % MinObjAlignment == 0, "unaligned size");
 330   assert(Universe::heap()->is_in_reserved(start), "not in heap");
 331   assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");
 332 }
 333 
 334 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
 335 {
 336   if (ZapFillerObjects && zap) {
 337     Copy::fill_to_words(start + filler_array_hdr_size(),
 338                         words - filler_array_hdr_size(), 0XDEAFBABE);
 339   }
 340 }
 341 #endif // ASSERT
 342 
 343 void
 344 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
 345 {
 346   assert(words >= filler_array_min_size(), "too small for an array");
 347   assert(words <= filler_array_max_size(), "too big for a single object");
 348 
 349   const size_t payload_size = words - filler_array_hdr_size();
 350   const size_t len = payload_size * HeapWordSize / sizeof(jint);
 351   assert((int)len >= 0, err_msg("size too large " SIZE_FORMAT " becomes %d", words, (int)len));
 352 
 353   // Set the length first for concurrent GC.
 354   ((arrayOop)start)->set_length((int)len);
 355   post_allocation_setup_common(Universe::intArrayKlassObj(), start);
 356   DEBUG_ONLY(zap_filler_array(start, words, zap);)
 357 }
 358 
 359 void
 360 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
 361 {
 362   assert(words <= filler_array_max_size(), "too big for a single object");
 363 
 364   if (words >= filler_array_min_size()) {
 365     fill_with_array(start, words, zap);
 366   } else if (words > 0) {
 367     assert(words == min_fill_size(), "unaligned size");
 368     post_allocation_setup_common(SystemDictionary::Object_klass(), start);
 369   }
 370 }
 371 
 372 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
 373 {
 374   DEBUG_ONLY(fill_args_check(start, words);)
 375   HandleMark hm;  // Free handles before leaving.
 376   fill_with_object_impl(start, words, zap);
 377 }
 378 
 379 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
 380 {
 381   DEBUG_ONLY(fill_args_check(start, words);)
 382   HandleMark hm;  // Free handles before leaving.
 383 
 384 #ifdef _LP64
 385   // A single array can fill ~8G, so multiple objects are needed only in 64-bit.
 386   // First fill with arrays, ensuring that any remaining space is big enough to
 387   // fill.  The remainder is filled with a single object.
 388   const size_t min = min_fill_size();
 389   const size_t max = filler_array_max_size();
 390   while (words > max) {
 391     const size_t cur = words - max >= min ? max : max - min;
 392     fill_with_array(start, cur, zap);
 393     start += cur;
 394     words -= cur;
 395   }
 396 #endif
 397 
 398   fill_with_object_impl(start, words, zap);
 399 }
 400 
 401 HeapWord* CollectedHeap::allocate_new_tlab(size_t size) {
 402   guarantee(false, "thread-local allocation buffers not supported");
 403   return NULL;
 404 }
 405 
 406 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
 407   // The second disjunct in the assertion below makes a concession
 408   // for the start-up verification done while the VM is being
 409   // created. Callers be careful that you know that mutators
 410   // aren't going to interfere -- for instance, this is permissible
 411   // if we are still single-threaded and have either not yet
 412   // started allocating (nothing much to verify) or we have
 413   // started allocating but are now a full-fledged JavaThread
 414   // (and have thus made our TLAB's) available for filling.
 415   assert(SafepointSynchronize::is_at_safepoint() ||
 416          !is_init_completed(),
 417          "Should only be called at a safepoint or at start-up"
 418          " otherwise concurrent mutator activity may make heap "
 419          " unparsable again");
 420   const bool use_tlab = UseTLAB;
 421   const bool deferred = _defer_initial_card_mark;
 422   // The main thread starts allocating via a TLAB even before it
 423   // has added itself to the threads list at vm boot-up.
 424   assert(!use_tlab || Threads::first() != NULL,
 425          "Attempt to fill tlabs before main thread has been added"
 426          " to threads list is doomed to failure!");
 427   for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
 428      if (use_tlab) thread->tlab().make_parsable(retire_tlabs);
 429 #ifdef COMPILER2
 430      // The deferred store barriers must all have been flushed to the
 431      // card-table (or other remembered set structure) before GC starts
 432      // processing the card-table (or other remembered set).
 433      if (deferred) flush_deferred_store_barrier(thread);
 434 #else
 435      assert(!deferred, "Should be false");
 436      assert(thread->deferred_card_mark().is_empty(), "Should be empty");
 437 #endif
 438   }
 439 }
 440 
 441 void CollectedHeap::accumulate_statistics_all_tlabs() {
 442   if (UseTLAB) {
 443     assert(SafepointSynchronize::is_at_safepoint() ||
 444          !is_init_completed(),
 445          "should only accumulate statistics on tlabs at safepoint");
 446 
 447     ThreadLocalAllocBuffer::accumulate_statistics_before_gc();
 448   }
 449 }
 450 
 451 void CollectedHeap::resize_all_tlabs() {
 452   if (UseTLAB) {
 453     assert(SafepointSynchronize::is_at_safepoint() ||
 454          !is_init_completed(),
 455          "should only resize tlabs at safepoint");
 456 
 457     ThreadLocalAllocBuffer::resize_all_tlabs();
 458   }
 459 }
 460 
 461 void CollectedHeap::pre_full_gc_dump() {
 462   if (HeapDumpBeforeFullGC) {
 463     TraceTime tt("Heap Dump (before full gc): ", PrintGCDetails, false, gclog_or_tty);
 464     // We are doing a "major" collection and a heap dump before
 465     // major collection has been requested.
 466     HeapDumper::dump_heap();
 467   }
 468   if (PrintClassHistogramBeforeFullGC) {
 469     TraceTime tt("Class Histogram (before full gc): ", PrintGCDetails, true, gclog_or_tty);
 470     VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
 471     inspector.doit();
 472   }
 473 }
 474 
 475 void CollectedHeap::post_full_gc_dump() {
 476   if (HeapDumpAfterFullGC) {
 477     TraceTime tt("Heap Dump (after full gc): ", PrintGCDetails, false, gclog_or_tty);
 478     HeapDumper::dump_heap();
 479   }
 480   if (PrintClassHistogramAfterFullGC) {
 481     TraceTime tt("Class Histogram (after full gc): ", PrintGCDetails, true, gclog_or_tty);
 482     VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
 483     inspector.doit();
 484   }
 485 }
 486 
 487 oop CollectedHeap::Class_obj_allocate(KlassHandle klass, int size, KlassHandle real_klass, TRAPS) {
 488   debug_only(check_for_valid_allocation_state());
 489   assert(!Universe::heap()->is_gc_active(), "Allocation during gc not allowed");
 490   assert(size >= 0, "int won't convert to size_t");
 491   HeapWord* obj;
 492     assert(ScavengeRootsInCode > 0, "must be");
 493     obj = common_mem_allocate_init(size, CHECK_NULL);
 494   post_allocation_setup_common(klass, obj);
 495   assert(Universe::is_bootstrapping() ||
 496          !((oop)obj)->is_array(), "must not be an array");
 497   NOT_PRODUCT(Universe::heap()->check_for_bad_heap_word_value(obj, size));
 498   oop mirror = (oop)obj;
 499 
 500   java_lang_Class::set_oop_size(mirror, size);
 501 
 502   // Setup indirections
 503   if (!real_klass.is_null()) {
 504     java_lang_Class::set_klass(mirror, real_klass());
 505     real_klass->set_java_mirror(mirror);
 506   }
 507 
 508   InstanceMirrorKlass* mk = InstanceMirrorKlass::cast(mirror->klass());
 509   assert(size == mk->instance_size(real_klass), "should have been set");
 510 
 511   // notify jvmti and dtrace
 512   post_allocation_notify(klass, (oop)obj);
 513 
 514   return mirror;
 515 }
 516 
 517 /////////////// Unit tests ///////////////
 518 
 519 #ifndef PRODUCT
 520 void CollectedHeap::test_is_in() {
 521   CollectedHeap* heap = Universe::heap();
 522 
 523   uintptr_t epsilon    = (uintptr_t) MinObjAlignment;
 524   uintptr_t heap_start = (uintptr_t) heap->_reserved.start();
 525   uintptr_t heap_end   = (uintptr_t) heap->_reserved.end();
 526 
 527   // Test that NULL is not in the heap.
 528   assert(!heap->is_in(NULL), "NULL is unexpectedly in the heap");
 529 
 530   // Test that a pointer to before the heap start is reported as outside the heap.
 531   assert(heap_start >= ((uintptr_t)NULL + epsilon), "sanity");
 532   void* before_heap = (void*)(heap_start - epsilon);
 533   assert(!heap->is_in(before_heap),
 534       err_msg("before_heap: " PTR_FORMAT " is unexpectedly in the heap", before_heap));
 535 
 536   // Test that a pointer to after the heap end is reported as outside the heap.
 537   assert(heap_end <= ((uintptr_t)-1 - epsilon), "sanity");
 538   void* after_heap = (void*)(heap_end + epsilon);
 539   assert(!heap->is_in(after_heap),
 540       err_msg("after_heap: " PTR_FORMAT " is unexpectedly in the heap", after_heap));
 541 }
 542 #endif