1 /* 2 * Copyright (c) 2018, 2023, 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 "classfile/vmClasses.hpp" 28 #include "gc/shared/allocTracer.hpp" 29 #include "gc/shared/collectedHeap.hpp" 30 #include "gc/shared/memAllocator.hpp" 31 #include "gc/shared/threadLocalAllocBuffer.inline.hpp" 32 #include "gc/shared/tlab_globals.hpp" 33 #include "memory/universe.hpp" 34 #include "oops/arrayOop.hpp" 35 #include "oops/oop.inline.hpp" 36 #include "prims/jvmtiExport.hpp" 37 #include "runtime/continuationJavaClasses.inline.hpp" 38 #include "runtime/handles.inline.hpp" 39 #include "runtime/sharedRuntime.hpp" 40 #include "runtime/javaThread.hpp" 41 #include "services/lowMemoryDetector.hpp" 42 #include "utilities/align.hpp" 43 #include "utilities/copy.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(JavaThread* thread); 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(JavaThread* thread); 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::current()), 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 verify_before(); 81 } 82 83 ~Allocation() { 84 if (!check_out_of_memory()) { 85 notify_allocation(_thread); 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 = nullptr; 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() != nullptr) { 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 #ifdef ASSERT 152 void MemAllocator::Allocation::check_for_valid_allocation_state() const { 153 // How to choose between a pending exception and a potential 154 // OutOfMemoryError? Don't allow pending exceptions. 155 // This is a VM policy failure, so how do we exhaustively test it? 156 assert(!_thread->has_pending_exception(), 157 "shouldn't be allocating with pending exception"); 158 // Allocation of an oop can always invoke a safepoint. 159 JavaThread::cast(_thread)->check_for_valid_safepoint_state(); 160 } 161 #endif 162 163 void MemAllocator::Allocation::notify_allocation_jvmti_sampler() { 164 // support for JVMTI VMObjectAlloc event (no-op if not enabled) 165 JvmtiExport::vm_object_alloc_event_collector(obj()); 166 167 if (!JvmtiExport::should_post_sampled_object_alloc()) { 168 // Sampling disabled 169 return; 170 } 171 172 if (!_allocated_outside_tlab && _allocated_tlab_size == 0 && !_tlab_end_reset_for_sample) { 173 // Sample if it's a non-TLAB allocation, or a TLAB allocation that either refills the TLAB 174 // or expands it due to taking a sampler induced slow path. 175 return; 176 } 177 178 // If we want to be sampling, protect the allocated object with a Handle 179 // before doing the callback. The callback is done in the destructor of 180 // the JvmtiSampledObjectAllocEventCollector. 181 size_t bytes_since_last = 0; 182 183 { 184 PreserveObj obj_h(_thread, _obj_ptr); 185 JvmtiSampledObjectAllocEventCollector collector; 186 size_t size_in_bytes = _allocator._word_size * HeapWordSize; 187 ThreadLocalAllocBuffer& tlab = _thread->tlab(); 188 189 if (!_allocated_outside_tlab) { 190 bytes_since_last = tlab.bytes_since_last_sample_point(); 191 } 192 193 _thread->heap_sampler().check_for_sampling(obj_h(), size_in_bytes, bytes_since_last); 194 } 195 196 if (_tlab_end_reset_for_sample || _allocated_tlab_size != 0) { 197 // Tell tlab to forget bytes_since_last if we passed it to the heap sampler. 198 _thread->tlab().set_sample_end(bytes_since_last != 0); 199 } 200 } 201 202 void MemAllocator::Allocation::notify_allocation_low_memory_detector() { 203 // support low memory notifications (no-op if not enabled) 204 LowMemoryDetector::detect_low_memory_for_collected_pools(); 205 } 206 207 void MemAllocator::Allocation::notify_allocation_jfr_sampler() { 208 HeapWord* mem = cast_from_oop<HeapWord*>(obj()); 209 size_t size_in_bytes = _allocator._word_size * HeapWordSize; 210 211 if (_allocated_outside_tlab) { 212 AllocTracer::send_allocation_outside_tlab(obj()->klass(), mem, size_in_bytes, _thread); 213 } else if (_allocated_tlab_size != 0) { 214 // TLAB was refilled 215 AllocTracer::send_allocation_in_new_tlab(obj()->klass(), mem, _allocated_tlab_size * HeapWordSize, 216 size_in_bytes, _thread); 217 } 218 } 219 220 void MemAllocator::Allocation::notify_allocation_dtrace_sampler(JavaThread* thread) { 221 if (DTraceAllocProbes) { 222 // support for Dtrace object alloc event (no-op most of the time) 223 Klass* klass = obj()->klass(); 224 size_t word_size = _allocator._word_size; 225 if (klass != nullptr && klass->name() != nullptr) { 226 SharedRuntime::dtrace_object_alloc(thread, obj(), word_size); 227 } 228 } 229 } 230 231 void MemAllocator::Allocation::notify_allocation(JavaThread* thread) { 232 notify_allocation_low_memory_detector(); 233 notify_allocation_jfr_sampler(); 234 notify_allocation_dtrace_sampler(thread); 235 notify_allocation_jvmti_sampler(); 236 } 237 238 HeapWord* MemAllocator::mem_allocate_outside_tlab(Allocation& allocation) const { 239 allocation._allocated_outside_tlab = true; 240 HeapWord* mem = Universe::heap()->mem_allocate(_word_size, &allocation._overhead_limit_exceeded); 241 if (mem == nullptr) { 242 return mem; 243 } 244 245 size_t size_in_bytes = _word_size * HeapWordSize; 246 _thread->incr_allocated_bytes(size_in_bytes); 247 248 return mem; 249 } 250 251 HeapWord* MemAllocator::mem_allocate_inside_tlab(Allocation& allocation) const { 252 assert(UseTLAB, "should use UseTLAB"); 253 254 // Try allocating from an existing TLAB. 255 HeapWord* mem = mem_allocate_inside_tlab_fast(); 256 if (mem != nullptr) { 257 return mem; 258 } 259 260 // Try refilling the TLAB and allocating the object in it. 261 return mem_allocate_inside_tlab_slow(allocation); 262 } 263 264 HeapWord* MemAllocator::mem_allocate_inside_tlab_fast() const { 265 return _thread->tlab().allocate(_word_size); 266 } 267 268 HeapWord* MemAllocator::mem_allocate_inside_tlab_slow(Allocation& allocation) const { 269 HeapWord* mem = nullptr; 270 ThreadLocalAllocBuffer& tlab = _thread->tlab(); 271 272 if (JvmtiExport::should_post_sampled_object_alloc()) { 273 tlab.set_back_allocation_end(); 274 mem = tlab.allocate(_word_size); 275 276 // We set back the allocation sample point to try to allocate this, reset it 277 // when done. 278 allocation._tlab_end_reset_for_sample = true; 279 280 if (mem != nullptr) { 281 return mem; 282 } 283 } 284 285 // Retain tlab and allocate object in shared space if 286 // the amount free in the tlab is too large to discard. 287 if (tlab.free() > tlab.refill_waste_limit()) { 288 tlab.record_slow_allocation(_word_size); 289 return nullptr; 290 } 291 292 // Discard tlab and allocate a new one. 293 // To minimize fragmentation, the last TLAB may be smaller than the rest. 294 size_t new_tlab_size = tlab.compute_size(_word_size); 295 296 tlab.retire_before_allocation(); 297 298 if (new_tlab_size == 0) { 299 return nullptr; 300 } 301 302 // Allocate a new TLAB requesting new_tlab_size. Any size 303 // between minimal and new_tlab_size is accepted. 304 size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size); 305 mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size); 306 if (mem == nullptr) { 307 assert(allocation._allocated_tlab_size == 0, 308 "Allocation failed, but actual size was updated. min: " SIZE_FORMAT 309 ", desired: " SIZE_FORMAT ", actual: " SIZE_FORMAT, 310 min_tlab_size, new_tlab_size, allocation._allocated_tlab_size); 311 return nullptr; 312 } 313 assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: " 314 PTR_FORMAT " min: " SIZE_FORMAT ", desired: " SIZE_FORMAT, 315 p2i(mem), min_tlab_size, new_tlab_size); 316 317 if (ZeroTLAB) { 318 // ..and clear it. 319 Copy::zero_to_words(mem, allocation._allocated_tlab_size); 320 } else { 321 // ...and zap just allocated object. 322 #ifdef ASSERT 323 // Skip mangling the space corresponding to the object header to 324 // ensure that the returned space is not considered parsable by 325 // any concurrent GC thread. 326 size_t hdr_size = oopDesc::header_size(); 327 Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal); 328 #endif // ASSERT 329 } 330 331 tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size); 332 return mem; 333 } 334 335 336 HeapWord* MemAllocator::mem_allocate_slow(Allocation& allocation) const { 337 // Allocation of an oop can always invoke a safepoint. 338 debug_only(JavaThread::cast(_thread)->check_for_valid_safepoint_state()); 339 340 if (UseTLAB) { 341 // Try refilling the TLAB and allocating the object in it. 342 HeapWord* mem = mem_allocate_inside_tlab_slow(allocation); 343 if (mem != nullptr) { 344 return mem; 345 } 346 } 347 348 return mem_allocate_outside_tlab(allocation); 349 } 350 351 HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const { 352 if (UseTLAB) { 353 // Try allocating from an existing TLAB. 354 HeapWord* mem = mem_allocate_inside_tlab_fast(); 355 if (mem != nullptr) { 356 return mem; 357 } 358 } 359 360 return mem_allocate_slow(allocation); 361 } 362 363 oop MemAllocator::allocate() const { 364 oop obj = nullptr; 365 { 366 Allocation allocation(*this, &obj); 367 HeapWord* mem = mem_allocate(allocation); 368 if (mem != nullptr) { 369 obj = initialize(mem); 370 } else { 371 // The unhandled oop detector will poison local variable obj, 372 // so reset it to null if mem is null. 373 obj = nullptr; 374 } 375 } 376 return obj; 377 } 378 379 void MemAllocator::mem_clear(HeapWord* mem) const { 380 assert(mem != nullptr, "cannot initialize null object"); 381 const size_t hs = oopDesc::header_size(); 382 assert(_word_size >= hs, "unexpected object size"); 383 oopDesc::set_klass_gap(mem, 0); 384 Copy::fill_to_aligned_words(mem + hs, _word_size - hs); 385 } 386 387 oop MemAllocator::finish(HeapWord* mem) const { 388 assert(mem != nullptr, "null object pointer"); 389 // May be bootstrapping 390 oopDesc::set_mark(mem, markWord::prototype()); 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 oop ObjArrayAllocator::initialize(HeapWord* mem) const { 404 // Set array length before setting the _klass field because a 405 // non-null klass field indicates that the object is parsable by 406 // concurrent GC. 407 assert(_length >= 0, "length should be non-negative"); 408 if (_do_zero) { 409 mem_clear(mem); 410 } 411 arrayOopDesc::set_length(mem, _length); 412 return finish(mem); 413 } 414 415 oop ClassAllocator::initialize(HeapWord* mem) const { 416 // Set oop_size field before setting the _klass field because a 417 // non-null _klass field indicates that the object is parsable by 418 // concurrent GC. 419 assert(_word_size > 0, "oop_size must be positive."); 420 mem_clear(mem); 421 java_lang_Class::set_oop_size(mem, _word_size); 422 return finish(mem); 423 } --- EOF ---