1 /* 2 * Copyright (c) 2018, 2025, 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 "classfile/javaClasses.hpp" 26 #include "classfile/vmClasses.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/continuationJavaClasses.inline.hpp" 37 #include "runtime/handles.inline.hpp" 38 #include "runtime/sharedRuntime.hpp" 39 #include "runtime/javaThread.hpp" 40 #include "services/lowMemoryDetector.hpp" 41 #include "utilities/align.hpp" 42 #include "utilities/copy.hpp" 43 #include "utilities/globalDefinitions.hpp" 44 45 class MemAllocator::Allocation: StackObj { 46 friend class MemAllocator; 47 48 const MemAllocator& _allocator; 49 JavaThread* _thread; 50 oop* _obj_ptr; 51 bool _overhead_limit_exceeded; 52 bool _allocated_outside_tlab; 53 size_t _allocated_tlab_size; 54 bool _tlab_end_reset_for_sample; 55 56 bool check_out_of_memory(); 57 void verify_before(); 58 void verify_after(); 59 void notify_allocation(); 60 void notify_allocation_jvmti_sampler(); 61 void notify_allocation_low_memory_detector(); 62 void notify_allocation_jfr_sampler(); 63 void notify_allocation_dtrace_sampler(); 64 #ifdef ASSERT 65 void check_for_valid_allocation_state() const; 66 #endif 67 68 class PreserveObj; 69 70 public: 71 Allocation(const MemAllocator& allocator, oop* obj_ptr) 72 : _allocator(allocator), 73 _thread(JavaThread::cast(allocator._thread)), // Do not use Allocation in non-JavaThreads. 74 _obj_ptr(obj_ptr), 75 _overhead_limit_exceeded(false), 76 _allocated_outside_tlab(false), 77 _allocated_tlab_size(0), 78 _tlab_end_reset_for_sample(false) 79 { 80 assert(Thread::current() == allocator._thread, "do not pass MemAllocator across threads"); 81 verify_before(); 82 } 83 84 ~Allocation() { 85 if (!check_out_of_memory()) { 86 notify_allocation(); 87 } 88 } 89 90 oop obj() const { return *_obj_ptr; } 91 }; 92 93 class MemAllocator::Allocation::PreserveObj: StackObj { 94 HandleMark _handle_mark; 95 Handle _handle; 96 oop* const _obj_ptr; 97 98 public: 99 PreserveObj(JavaThread* thread, oop* obj_ptr) 100 : _handle_mark(thread), 101 _handle(thread, *obj_ptr), 102 _obj_ptr(obj_ptr) 103 { 104 *obj_ptr = nullptr; 105 } 106 107 ~PreserveObj() { 108 *_obj_ptr = _handle(); 109 } 110 111 oop operator()() const { 112 return _handle(); 113 } 114 }; 115 116 bool MemAllocator::Allocation::check_out_of_memory() { 117 JavaThread* THREAD = _thread; // For exception macros. 118 assert(!HAS_PENDING_EXCEPTION, "Unexpected exception, will result in uninitialized storage"); 119 120 if (obj() != nullptr) { 121 return false; 122 } 123 124 const char* message = _overhead_limit_exceeded ? "GC overhead limit exceeded" : "Java heap space"; 125 if (!_thread->is_in_internal_oome_mark()) { 126 // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError support 127 report_java_out_of_memory(message); 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 } 133 134 oop exception = _overhead_limit_exceeded ? 135 Universe::out_of_memory_error_gc_overhead_limit() : 136 Universe::out_of_memory_error_java_heap(); 137 THROW_OOP_(exception, true); 138 } else { 139 THROW_OOP_(Universe::out_of_memory_error_java_heap_without_backtrace(), true); 140 } 141 } 142 143 void MemAllocator::Allocation::verify_before() { 144 // Clear unhandled oops for memory allocation. Memory allocation might 145 // not take out a lock if from tlab, so clear here. 146 JavaThread* THREAD = _thread; // For exception macros. 147 assert(!HAS_PENDING_EXCEPTION, "Should not allocate with exception pending"); 148 debug_only(check_for_valid_allocation_state()); 149 assert(!Universe::heap()->is_stw_gc_active(), "Allocation during GC pause not allowed"); 150 } 151 152 #ifdef ASSERT 153 void MemAllocator::Allocation::check_for_valid_allocation_state() const { 154 // How to choose between a pending exception and a potential 155 // OutOfMemoryError? Don't allow pending exceptions. 156 // This is a VM policy failure, so how do we exhaustively test it? 157 assert(!_thread->has_pending_exception(), 158 "shouldn't be allocating with pending exception"); 159 // Allocation of an oop can always invoke a safepoint. 160 _thread->check_for_valid_safepoint_state(); 161 } 162 #endif 163 164 void MemAllocator::Allocation::notify_allocation_jvmti_sampler() { 165 // support for JVMTI VMObjectAlloc event (no-op if not enabled) 166 JvmtiExport::vm_object_alloc_event_collector(obj()); 167 168 if (!JvmtiExport::should_post_sampled_object_alloc()) { 169 // Sampling disabled 170 return; 171 } 172 173 if (!_allocated_outside_tlab && _allocated_tlab_size == 0 && !_tlab_end_reset_for_sample) { 174 // Sample if it's a non-TLAB allocation, or a TLAB allocation that either refills the TLAB 175 // or expands it due to taking a sampler induced slow path. 176 return; 177 } 178 179 // If we want to be sampling, protect the allocated object with a Handle 180 // before doing the callback. The callback is done in the destructor of 181 // the JvmtiSampledObjectAllocEventCollector. 182 size_t bytes_since_last = 0; 183 184 { 185 PreserveObj obj_h(_thread, _obj_ptr); 186 JvmtiSampledObjectAllocEventCollector collector; 187 size_t size_in_bytes = _allocator._word_size * HeapWordSize; 188 ThreadLocalAllocBuffer& tlab = _thread->tlab(); 189 190 if (!_allocated_outside_tlab) { 191 bytes_since_last = tlab.bytes_since_last_sample_point(); 192 } 193 194 _thread->heap_sampler().check_for_sampling(obj_h(), size_in_bytes, bytes_since_last); 195 } 196 197 if (_tlab_end_reset_for_sample || _allocated_tlab_size != 0) { 198 // Tell tlab to forget bytes_since_last if we passed it to the heap sampler. 199 _thread->tlab().set_sample_end(bytes_since_last != 0); 200 } 201 } 202 203 void MemAllocator::Allocation::notify_allocation_low_memory_detector() { 204 // support low memory notifications (no-op if not enabled) 205 LowMemoryDetector::detect_low_memory_for_collected_pools(); 206 } 207 208 void MemAllocator::Allocation::notify_allocation_jfr_sampler() { 209 HeapWord* mem = cast_from_oop<HeapWord*>(obj()); 210 size_t size_in_bytes = _allocator._word_size * HeapWordSize; 211 212 if (_allocated_outside_tlab) { 213 AllocTracer::send_allocation_outside_tlab(obj()->klass(), mem, size_in_bytes, _thread); 214 } else if (_allocated_tlab_size != 0) { 215 // TLAB was refilled 216 AllocTracer::send_allocation_in_new_tlab(obj()->klass(), mem, _allocated_tlab_size * HeapWordSize, 217 size_in_bytes, _thread); 218 } 219 } 220 221 void MemAllocator::Allocation::notify_allocation_dtrace_sampler() { 222 if (DTraceAllocProbes) { 223 // support for Dtrace object alloc event (no-op most of the time) 224 Klass* klass = obj()->klass(); 225 size_t word_size = _allocator._word_size; 226 if (klass != nullptr && klass->name() != nullptr) { 227 SharedRuntime::dtrace_object_alloc(_thread, obj(), word_size); 228 } 229 } 230 } 231 232 void MemAllocator::Allocation::notify_allocation() { 233 notify_allocation_low_memory_detector(); 234 notify_allocation_jfr_sampler(); 235 notify_allocation_dtrace_sampler(); 236 notify_allocation_jvmti_sampler(); 237 } 238 239 HeapWord* MemAllocator::mem_allocate_outside_tlab(Allocation& allocation) const { 240 allocation._allocated_outside_tlab = true; 241 HeapWord* mem = Universe::heap()->mem_allocate(_word_size, &allocation._overhead_limit_exceeded); 242 if (mem == nullptr) { 243 return mem; 244 } 245 246 size_t size_in_bytes = _word_size * HeapWordSize; 247 _thread->incr_allocated_bytes(size_in_bytes); 248 249 return mem; 250 } 251 252 HeapWord* MemAllocator::mem_allocate_inside_tlab_fast() const { 253 return _thread->tlab().allocate(_word_size); 254 } 255 256 HeapWord* MemAllocator::mem_allocate_inside_tlab_slow(Allocation& allocation) const { 257 HeapWord* mem = nullptr; 258 ThreadLocalAllocBuffer& tlab = _thread->tlab(); 259 260 if (JvmtiExport::should_post_sampled_object_alloc()) { 261 tlab.set_back_allocation_end(); 262 mem = tlab.allocate(_word_size); 263 264 // We set back the allocation sample point to try to allocate this, reset it 265 // when done. 266 allocation._tlab_end_reset_for_sample = true; 267 268 if (mem != nullptr) { 269 return mem; 270 } 271 } 272 273 // Retain tlab and allocate object in shared space if 274 // the amount free in the tlab is too large to discard. 275 if (tlab.free() > tlab.refill_waste_limit()) { 276 tlab.record_slow_allocation(_word_size); 277 return nullptr; 278 } 279 280 // Discard tlab and allocate a new one. 281 // To minimize fragmentation, the last TLAB may be smaller than the rest. 282 size_t new_tlab_size = tlab.compute_size(_word_size); 283 284 tlab.retire_before_allocation(); 285 286 if (new_tlab_size == 0) { 287 return nullptr; 288 } 289 290 // Allocate a new TLAB requesting new_tlab_size. Any size 291 // between minimal and new_tlab_size is accepted. 292 size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size); 293 mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size); 294 if (mem == nullptr) { 295 assert(allocation._allocated_tlab_size == 0, 296 "Allocation failed, but actual size was updated. min: %zu" 297 ", desired: %zu, actual: %zu", 298 min_tlab_size, new_tlab_size, allocation._allocated_tlab_size); 299 return nullptr; 300 } 301 assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: " 302 PTR_FORMAT " min: %zu, desired: %zu", 303 p2i(mem), min_tlab_size, new_tlab_size); 304 305 // ...and clear or zap just allocated TLAB, if needed. 306 if (ZeroTLAB) { 307 Copy::zero_to_words(mem, allocation._allocated_tlab_size); 308 } else if (ZapTLAB) { 309 // Skip mangling the space corresponding to the object header to 310 // ensure that the returned space is not considered parsable by 311 // any concurrent GC thread. 312 size_t hdr_size = oopDesc::header_size(); 313 Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal); 314 } 315 316 tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size); 317 return mem; 318 } 319 320 HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const { 321 if (UseTLAB) { 322 // Try allocating from an existing TLAB. 323 HeapWord* mem = mem_allocate_inside_tlab_fast(); 324 if (mem != nullptr) { 325 return mem; 326 } 327 } 328 329 // Allocation of an oop can always invoke a safepoint. 330 debug_only(allocation._thread->check_for_valid_safepoint_state()); 331 332 if (UseTLAB) { 333 // Try refilling the TLAB and allocating the object in it. 334 HeapWord* mem = mem_allocate_inside_tlab_slow(allocation); 335 if (mem != nullptr) { 336 return mem; 337 } 338 } 339 340 return mem_allocate_outside_tlab(allocation); 341 } 342 343 oop MemAllocator::allocate() const { 344 oop obj = nullptr; 345 { 346 Allocation allocation(*this, &obj); 347 HeapWord* mem = mem_allocate(allocation); 348 if (mem != nullptr) { 349 obj = initialize(mem); 350 } else { 351 // The unhandled oop detector will poison local variable obj, 352 // so reset it to null if mem is null. 353 obj = nullptr; 354 } 355 } 356 return obj; 357 } 358 359 void MemAllocator::mem_clear(HeapWord* mem) const { 360 assert(mem != nullptr, "cannot initialize null object"); 361 const size_t hs = oopDesc::header_size(); 362 assert(_word_size >= hs, "unexpected object size"); 363 if (oopDesc::has_klass_gap()) { 364 oopDesc::set_klass_gap(mem, 0); 365 } 366 Copy::fill_to_aligned_words(mem + hs, _word_size - hs); 367 } 368 369 oop MemAllocator::finish(HeapWord* mem) const { 370 assert(mem != nullptr, "null object pointer"); 371 // Need a release store to ensure array/class length, mark word, and 372 // object zeroing are visible before setting the klass non-null, for 373 // concurrent collectors. 374 if (UseCompactObjectHeaders) { 375 oopDesc::release_set_mark(mem, _klass->prototype_header()); 376 } else { 377 oopDesc::set_mark(mem, markWord::prototype()); 378 oopDesc::release_set_klass(mem, _klass); 379 } 380 return cast_to_oop(mem); 381 } 382 383 oop ObjAllocator::initialize(HeapWord* mem) const { 384 mem_clear(mem); 385 return finish(mem); 386 } 387 388 oop ObjArrayAllocator::initialize(HeapWord* mem) const { 389 // Set array length before setting the _klass field because a 390 // non-null klass field indicates that the object is parsable by 391 // concurrent GC. 392 assert(_length >= 0, "length should be non-negative"); 393 if (_do_zero) { 394 mem_clear(mem); 395 mem_zap_start_padding(mem); 396 mem_zap_end_padding(mem); 397 } 398 arrayOopDesc::set_length(mem, _length); 399 return finish(mem); 400 } 401 402 #ifndef PRODUCT 403 void ObjArrayAllocator::mem_zap_start_padding(HeapWord* mem) const { 404 const BasicType element_type = ArrayKlass::cast(_klass)->element_type(); 405 const size_t base_offset_in_bytes = arrayOopDesc::base_offset_in_bytes(element_type); 406 const size_t header_size_in_bytes = arrayOopDesc::header_size_in_bytes(); 407 408 const address base = reinterpret_cast<address>(mem) + base_offset_in_bytes; 409 const address header_end = reinterpret_cast<address>(mem) + header_size_in_bytes; 410 411 if (header_end < base) { 412 const size_t padding_in_bytes = base - header_end; 413 Copy::fill_to_bytes(header_end, padding_in_bytes, heapPaddingByteVal); 414 } 415 } 416 417 void ObjArrayAllocator::mem_zap_end_padding(HeapWord* mem) const { 418 const size_t length_in_bytes = static_cast<size_t>(_length) << ArrayKlass::cast(_klass)->log2_element_size(); 419 const BasicType element_type = ArrayKlass::cast(_klass)->element_type(); 420 const size_t base_offset_in_bytes = arrayOopDesc::base_offset_in_bytes(element_type); 421 const size_t size_in_bytes = _word_size * BytesPerWord; 422 423 const address obj_end = reinterpret_cast<address>(mem) + size_in_bytes; 424 const address base = reinterpret_cast<address>(mem) + base_offset_in_bytes; 425 const address elements_end = base + length_in_bytes; 426 assert(elements_end <= obj_end, "payload must fit in object"); 427 if (elements_end < obj_end) { 428 const size_t padding_in_bytes = obj_end - elements_end; 429 Copy::fill_to_bytes(elements_end, padding_in_bytes, heapPaddingByteVal); 430 } 431 } 432 #endif 433 434 oop ClassAllocator::initialize(HeapWord* mem) const { 435 // Set oop_size field before setting the _klass field because a 436 // non-null _klass field indicates that the object is parsable by 437 // concurrent GC. 438 assert(_base_size > 0, "oop_size must be positive."); 439 mem_clear(mem); 440 java_lang_Class::set_oop_size(mem, _base_size); 441 return finish(mem); 442 }