1 /* 2 * Copyright (c) 2018, 2021, 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/javaClasses.hpp" 27 #include "gc/shared/allocTracer.hpp" 28 #include "gc/shared/collectedHeap.hpp" 29 #include "gc/shared/memAllocator.hpp" 30 #include "gc/shared/threadLocalAllocBuffer.inline.hpp" 31 #include "gc/shared/tlab_globals.hpp" 32 #include "memory/universe.hpp" 33 #include "oops/arrayOop.hpp" 34 #include "oops/oop.inline.hpp" 35 #include "prims/jvmtiExport.hpp" 36 #include "runtime/sharedRuntime.hpp" 37 #include "runtime/handles.inline.hpp" 38 #include "runtime/thread.inline.hpp" 39 #include "services/lowMemoryDetector.hpp" 40 #include "utilities/align.hpp" 41 #include "utilities/copy.hpp" 42 43 class MemAllocator::Allocation: StackObj { 44 friend class MemAllocator; 45 46 const MemAllocator& _allocator; 47 JavaThread* _thread; 48 oop* _obj_ptr; 49 bool _overhead_limit_exceeded; 50 bool _allocated_outside_tlab; 51 size_t _allocated_tlab_size; 52 bool _tlab_end_reset_for_sample; 53 54 bool check_out_of_memory(); 55 void verify_before(); 56 void verify_after(); 57 void notify_allocation(); 58 void notify_allocation_jvmti_sampler(); 59 void notify_allocation_low_memory_detector(); 60 void notify_allocation_jfr_sampler(); 61 void notify_allocation_dtrace_sampler(); 62 void check_for_bad_heap_word_value() const; 63 #ifdef ASSERT 64 void check_for_valid_allocation_state() const; 65 #endif 66 67 class PreserveObj; 68 69 public: 70 Allocation(const MemAllocator& allocator, oop* obj_ptr) 71 : _allocator(allocator), 72 _thread(JavaThread::current()), 73 _obj_ptr(obj_ptr), 74 _overhead_limit_exceeded(false), 75 _allocated_outside_tlab(false), 76 _allocated_tlab_size(0), 77 _tlab_end_reset_for_sample(false) 78 { 79 verify_before(); 80 } 81 82 ~Allocation() { 83 if (!check_out_of_memory()) { 84 verify_after(); 85 notify_allocation(); 86 } 87 } 88 89 oop obj() const { return *_obj_ptr; } 90 }; 91 92 class MemAllocator::Allocation::PreserveObj: StackObj { 93 HandleMark _handle_mark; 94 Handle _handle; 95 oop* const _obj_ptr; 96 97 public: 98 PreserveObj(JavaThread* thread, oop* obj_ptr) 99 : _handle_mark(thread), 100 _handle(thread, *obj_ptr), 101 _obj_ptr(obj_ptr) 102 { 103 *obj_ptr = NULL; 104 } 105 106 ~PreserveObj() { 107 *_obj_ptr = _handle(); 108 } 109 110 oop operator()() const { 111 return _handle(); 112 } 113 }; 114 115 bool MemAllocator::Allocation::check_out_of_memory() { 116 JavaThread* THREAD = _thread; // For exception macros. 117 assert(!HAS_PENDING_EXCEPTION, "Unexpected exception, will result in uninitialized storage"); 118 119 if (obj() != NULL) { 120 return false; 121 } 122 123 const char* message = _overhead_limit_exceeded ? "GC overhead limit exceeded" : "Java heap space"; 124 if (!_thread->in_retryable_allocation()) { 125 // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError support 126 report_java_out_of_memory(message); 127 128 if (JvmtiExport::should_post_resource_exhausted()) { 129 JvmtiExport::post_resource_exhausted( 130 JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR | JVMTI_RESOURCE_EXHAUSTED_JAVA_HEAP, 131 message); 132 } 133 oop exception = _overhead_limit_exceeded ? 134 Universe::out_of_memory_error_gc_overhead_limit() : 135 Universe::out_of_memory_error_java_heap(); 136 THROW_OOP_(exception, true); 137 } else { 138 THROW_OOP_(Universe::out_of_memory_error_retry(), true); 139 } 140 } 141 142 void MemAllocator::Allocation::verify_before() { 143 // Clear unhandled oops for memory allocation. Memory allocation might 144 // not take out a lock if from tlab, so clear here. 145 JavaThread* THREAD = _thread; // For exception macros. 146 assert(!HAS_PENDING_EXCEPTION, "Should not allocate with exception pending"); 147 debug_only(check_for_valid_allocation_state()); 148 assert(!Universe::heap()->is_gc_active(), "Allocation during gc not allowed"); 149 } 150 151 void MemAllocator::Allocation::verify_after() { 152 NOT_PRODUCT(check_for_bad_heap_word_value();) 153 } 154 155 void MemAllocator::Allocation::check_for_bad_heap_word_value() const { 156 MemRegion obj_range = _allocator.obj_memory_range(obj()); 157 HeapWord* addr = obj_range.start(); 158 size_t size = obj_range.word_size(); 159 if (CheckMemoryInitialization && ZapUnusedHeapArea) { 160 for (size_t slot = 0; slot < size; slot += 1) { 161 assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal), 162 "Found badHeapWordValue in post-allocation check"); 163 } 164 } 165 } 166 167 #ifdef ASSERT 168 void MemAllocator::Allocation::check_for_valid_allocation_state() const { 169 // How to choose between a pending exception and a potential 170 // OutOfMemoryError? Don't allow pending exceptions. 171 // This is a VM policy failure, so how do we exhaustively test it? 172 assert(!_thread->has_pending_exception(), 173 "shouldn't be allocating with pending exception"); 174 // Allocation of an oop can always invoke a safepoint. 175 _thread->as_Java_thread()->check_for_valid_safepoint_state(); 176 } 177 #endif 178 179 void MemAllocator::Allocation::notify_allocation_jvmti_sampler() { 180 // support for JVMTI VMObjectAlloc event (no-op if not enabled) 181 JvmtiExport::vm_object_alloc_event_collector(obj()); 182 183 if (!JvmtiExport::should_post_sampled_object_alloc()) { 184 // Sampling disabled 185 return; 186 } 187 188 if (!_allocated_outside_tlab && _allocated_tlab_size == 0 && !_tlab_end_reset_for_sample) { 189 // Sample if it's a non-TLAB allocation, or a TLAB allocation that either refills the TLAB 190 // or expands it due to taking a sampler induced slow path. 191 return; 192 } 193 194 // If we want to be sampling, protect the allocated object with a Handle 195 // before doing the callback. The callback is done in the destructor of 196 // the JvmtiSampledObjectAllocEventCollector. 197 size_t bytes_since_last = 0; 198 199 { 200 PreserveObj obj_h(_thread, _obj_ptr); 201 JvmtiSampledObjectAllocEventCollector collector; 202 size_t size_in_bytes = _allocator._word_size * HeapWordSize; 203 ThreadLocalAllocBuffer& tlab = _thread->tlab(); 204 205 if (!_allocated_outside_tlab) { 206 bytes_since_last = tlab.bytes_since_last_sample_point(); 207 } 208 209 _thread->heap_sampler().check_for_sampling(obj_h(), size_in_bytes, bytes_since_last); 210 } 211 212 if (_tlab_end_reset_for_sample || _allocated_tlab_size != 0) { 213 // Tell tlab to forget bytes_since_last if we passed it to the heap sampler. 214 _thread->tlab().set_sample_end(bytes_since_last != 0); 215 } 216 } 217 218 void MemAllocator::Allocation::notify_allocation_low_memory_detector() { 219 // support low memory notifications (no-op if not enabled) 220 LowMemoryDetector::detect_low_memory_for_collected_pools(); 221 } 222 223 void MemAllocator::Allocation::notify_allocation_jfr_sampler() { 224 HeapWord* mem = cast_from_oop<HeapWord*>(obj()); 225 size_t size_in_bytes = _allocator._word_size * HeapWordSize; 226 227 if (_allocated_outside_tlab) { 228 AllocTracer::send_allocation_outside_tlab(obj()->klass(), mem, size_in_bytes, _thread); 229 } else if (_allocated_tlab_size != 0) { 230 // TLAB was refilled 231 AllocTracer::send_allocation_in_new_tlab(obj()->klass(), mem, _allocated_tlab_size * HeapWordSize, 232 size_in_bytes, _thread); 233 } 234 } 235 236 void MemAllocator::Allocation::notify_allocation_dtrace_sampler() { 237 if (DTraceAllocProbes) { 238 // support for Dtrace object alloc event (no-op most of the time) 239 Klass* klass = obj()->klass(); 240 size_t word_size = _allocator._word_size; 241 if (klass != NULL && klass->name() != NULL) { 242 SharedRuntime::dtrace_object_alloc(obj(), (int)word_size); 243 } 244 } 245 } 246 247 void MemAllocator::Allocation::notify_allocation() { 248 notify_allocation_low_memory_detector(); 249 notify_allocation_jfr_sampler(); 250 notify_allocation_dtrace_sampler(); 251 notify_allocation_jvmti_sampler(); 252 } 253 254 HeapWord* MemAllocator::allocate_outside_tlab(Allocation& allocation) const { 255 allocation._allocated_outside_tlab = true; 256 HeapWord* mem = Universe::heap()->mem_allocate(_word_size, &allocation._overhead_limit_exceeded); 257 if (mem == NULL) { 258 return mem; 259 } 260 261 NOT_PRODUCT(Universe::heap()->check_for_non_bad_heap_word_value(mem, _word_size)); 262 size_t size_in_bytes = _word_size * HeapWordSize; 263 _thread->incr_allocated_bytes(size_in_bytes); 264 265 return mem; 266 } 267 268 HeapWord* MemAllocator::allocate_inside_tlab(Allocation& allocation) const { 269 assert(UseTLAB, "should use UseTLAB"); 270 271 // Try allocating from an existing TLAB. 272 HeapWord* mem = _thread->tlab().allocate(_word_size); 273 if (mem != NULL) { 274 return mem; 275 } 276 277 // Try refilling the TLAB and allocating the object in it. 278 return allocate_inside_tlab_slow(allocation); 279 } 280 281 HeapWord* MemAllocator::allocate_inside_tlab_slow(Allocation& allocation) const { 282 HeapWord* mem = NULL; 283 ThreadLocalAllocBuffer& tlab = _thread->tlab(); 284 285 if (JvmtiExport::should_post_sampled_object_alloc()) { 286 tlab.set_back_allocation_end(); 287 mem = tlab.allocate(_word_size); 288 289 // We set back the allocation sample point to try to allocate this, reset it 290 // when done. 291 allocation._tlab_end_reset_for_sample = true; 292 293 if (mem != NULL) { 294 return mem; 295 } 296 } 297 298 // Retain tlab and allocate object in shared space if 299 // the amount free in the tlab is too large to discard. 300 if (tlab.free() > tlab.refill_waste_limit()) { 301 tlab.record_slow_allocation(_word_size); 302 return NULL; 303 } 304 305 // Discard tlab and allocate a new one. 306 // To minimize fragmentation, the last TLAB may be smaller than the rest. 307 size_t new_tlab_size = tlab.compute_size(_word_size); 308 309 tlab.retire_before_allocation(); 310 311 if (new_tlab_size == 0) { 312 return NULL; 313 } 314 315 // Allocate a new TLAB requesting new_tlab_size. Any size 316 // between minimal and new_tlab_size is accepted. 317 size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size); 318 mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size); 319 if (mem == NULL) { 320 assert(allocation._allocated_tlab_size == 0, 321 "Allocation failed, but actual size was updated. min: " SIZE_FORMAT 322 ", desired: " SIZE_FORMAT ", actual: " SIZE_FORMAT, 323 min_tlab_size, new_tlab_size, allocation._allocated_tlab_size); 324 return NULL; 325 } 326 assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: " 327 PTR_FORMAT " min: " SIZE_FORMAT ", desired: " SIZE_FORMAT, 328 p2i(mem), min_tlab_size, new_tlab_size); 329 330 if (ZeroTLAB) { 331 // ..and clear it. 332 Copy::zero_to_words(mem, allocation._allocated_tlab_size); 333 } else { 334 // ...and zap just allocated object. 335 #ifdef ASSERT 336 // Skip mangling the space corresponding to the object header to 337 // ensure that the returned space is not considered parsable by 338 // any concurrent GC thread. 339 size_t hdr_size = oopDesc::header_size(); 340 Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal); 341 #endif // ASSERT 342 } 343 344 tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size); 345 return mem; 346 } 347 348 HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const { 349 if (UseTLAB) { 350 HeapWord* result = allocate_inside_tlab(allocation); 351 if (result != NULL) { 352 return result; 353 } 354 } 355 356 return allocate_outside_tlab(allocation); 357 } 358 359 oop MemAllocator::allocate() const { 360 oop obj = NULL; 361 { 362 Allocation allocation(*this, &obj); 363 HeapWord* mem = mem_allocate(allocation); 364 if (mem != NULL) { 365 obj = initialize(mem); 366 } else { 367 // The unhandled oop detector will poison local variable obj, 368 // so reset it to NULL if mem is NULL. 369 obj = NULL; 370 } 371 } 372 return obj; 373 } 374 375 void MemAllocator::mem_clear(HeapWord* mem) const { 376 assert(mem != NULL, "cannot initialize NULL object"); 377 const size_t hs = oopDesc::header_size(); 378 assert(_word_size >= hs, "unexpected object size"); 379 oopDesc::set_klass_gap(mem, 0); 380 Copy::fill_to_aligned_words(mem + hs, _word_size - hs); 381 } 382 383 oop MemAllocator::finish(HeapWord* mem) const { 384 assert(mem != NULL, "NULL object pointer"); 385 if (UseBiasedLocking) { 386 oopDesc::set_mark(mem, _klass->prototype_header()); 387 } else { 388 // May be bootstrapping 389 oopDesc::set_mark(mem, markWord::prototype()); 390 } 391 // Need a release store to ensure array/class length, mark word, and 392 // object zeroing are visible before setting the klass non-NULL, for 393 // concurrent collectors. 394 oopDesc::release_set_klass(mem, _klass); 395 return cast_to_oop(mem); 396 } 397 398 oop ObjAllocator::initialize(HeapWord* mem) const { 399 mem_clear(mem); 400 return finish(mem); 401 } 402 403 MemRegion ObjArrayAllocator::obj_memory_range(oop obj) const { 404 if (_do_zero) { 405 return MemAllocator::obj_memory_range(obj); 406 } 407 ArrayKlass* array_klass = ArrayKlass::cast(_klass); 408 const size_t hs = arrayOopDesc::header_size(array_klass->element_type()); 409 return MemRegion(cast_from_oop<HeapWord*>(obj) + hs, _word_size - hs); 410 } 411 412 oop ObjArrayAllocator::initialize(HeapWord* mem) const { 413 // Set array length before setting the _klass field because a 414 // non-NULL klass field indicates that the object is parsable by 415 // concurrent GC. 416 assert(_length >= 0, "length should be non-negative"); 417 if (_do_zero) { 418 mem_clear(mem); 419 } 420 arrayOopDesc::set_length(mem, _length); 421 return finish(mem); 422 } 423 424 oop ClassAllocator::initialize(HeapWord* mem) const { 425 // Set oop_size field before setting the _klass field because a 426 // non-NULL _klass field indicates that the object is parsable by 427 // concurrent GC. 428 assert(_word_size > 0, "oop_size must be positive."); 429 mem_clear(mem); 430 java_lang_Class::set_oop_size(mem, (int)_word_size); 431 return finish(mem); 432 }