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