1 /*
2 * Copyright (c) 2018, 2024, 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 #include "utilities/globalDefinitions.hpp"
45
46 class MemAllocator::Allocation: StackObj {
47 friend class MemAllocator;
48
49 const MemAllocator& _allocator;
50 JavaThread* _thread;
51 oop* _obj_ptr;
52 bool _overhead_limit_exceeded;
53 bool _allocated_outside_tlab;
54 size_t _allocated_tlab_size;
55 bool _tlab_end_reset_for_sample;
56
57 bool check_out_of_memory();
58 void verify_before();
59 void verify_after();
60 void notify_allocation();
61 void notify_allocation_jvmti_sampler();
62 void notify_allocation_low_memory_detector();
63 void notify_allocation_jfr_sampler();
64 void notify_allocation_dtrace_sampler();
65 #ifdef ASSERT
66 void check_for_valid_allocation_state() const;
67 #endif
68
69 class PreserveObj;
70
71 public:
72 Allocation(const MemAllocator& allocator, oop* obj_ptr)
73 : _allocator(allocator),
74 _thread(JavaThread::cast(allocator._thread)), // Do not use Allocation in non-JavaThreads.
75 _obj_ptr(obj_ptr),
76 _overhead_limit_exceeded(false),
77 _allocated_outside_tlab(false),
78 _allocated_tlab_size(0),
79 _tlab_end_reset_for_sample(false)
80 {
81 assert(Thread::current() == allocator._thread, "do not pass MemAllocator across threads");
82 verify_before();
83 }
84
85 ~Allocation() {
86 if (!check_out_of_memory()) {
87 notify_allocation();
88 }
89 }
90
91 oop obj() const { return *_obj_ptr; }
92 };
93
94 class MemAllocator::Allocation::PreserveObj: StackObj {
95 HandleMark _handle_mark;
96 Handle _handle;
97 oop* const _obj_ptr;
98
99 public:
100 PreserveObj(JavaThread* thread, oop* obj_ptr)
101 : _handle_mark(thread),
102 _handle(thread, *obj_ptr),
103 _obj_ptr(obj_ptr)
104 {
105 *obj_ptr = nullptr;
106 }
107
108 ~PreserveObj() {
109 *_obj_ptr = _handle();
110 }
111
112 oop operator()() const {
113 return _handle();
114 }
115 };
116
117 bool MemAllocator::Allocation::check_out_of_memory() {
118 JavaThread* THREAD = _thread; // For exception macros.
119 assert(!HAS_PENDING_EXCEPTION, "Unexpected exception, will result in uninitialized storage");
120
121 if (obj() != nullptr) {
122 return false;
123 }
124
125 const char* message = _overhead_limit_exceeded ? "GC overhead limit exceeded" : "Java heap space";
126 if (!_thread->is_in_internal_oome_mark()) {
127 // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError support
128 report_java_out_of_memory(message);
129 if (JvmtiExport::should_post_resource_exhausted()) {
130 JvmtiExport::post_resource_exhausted(
131 JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR | JVMTI_RESOURCE_EXHAUSTED_JAVA_HEAP,
132 message);
133 }
134
135 oop exception = _overhead_limit_exceeded ?
136 Universe::out_of_memory_error_gc_overhead_limit() :
137 Universe::out_of_memory_error_java_heap();
138 THROW_OOP_(exception, true);
139 } else {
140 THROW_OOP_(Universe::out_of_memory_error_java_heap_without_backtrace(), true);
141 }
142 }
143
144 void MemAllocator::Allocation::verify_before() {
145 // Clear unhandled oops for memory allocation. Memory allocation might
146 // not take out a lock if from tlab, so clear here.
147 JavaThread* THREAD = _thread; // For exception macros.
148 assert(!HAS_PENDING_EXCEPTION, "Should not allocate with exception pending");
149 debug_only(check_for_valid_allocation_state());
150 assert(!Universe::heap()->is_stw_gc_active(), "Allocation during GC pause not allowed");
151 }
152
153 #ifdef ASSERT
154 void MemAllocator::Allocation::check_for_valid_allocation_state() const {
155 // How to choose between a pending exception and a potential
156 // OutOfMemoryError? Don't allow pending exceptions.
157 // This is a VM policy failure, so how do we exhaustively test it?
158 assert(!_thread->has_pending_exception(),
159 "shouldn't be allocating with pending exception");
160 // Allocation of an oop can always invoke a safepoint.
161 _thread->check_for_valid_safepoint_state();
162 }
163 #endif
164
165 void MemAllocator::Allocation::notify_allocation_jvmti_sampler() {
166 // support for JVMTI VMObjectAlloc event (no-op if not enabled)
167 JvmtiExport::vm_object_alloc_event_collector(obj());
168
169 if (!JvmtiExport::should_post_sampled_object_alloc()) {
170 // Sampling disabled
171 return;
172 }
173
174 if (!_allocated_outside_tlab && _allocated_tlab_size == 0 && !_tlab_end_reset_for_sample) {
175 // Sample if it's a non-TLAB allocation, or a TLAB allocation that either refills the TLAB
176 // or expands it due to taking a sampler induced slow path.
177 return;
178 }
179
180 // If we want to be sampling, protect the allocated object with a Handle
181 // before doing the callback. The callback is done in the destructor of
182 // the JvmtiSampledObjectAllocEventCollector.
183 size_t bytes_since_last = 0;
184
185 {
186 PreserveObj obj_h(_thread, _obj_ptr);
187 JvmtiSampledObjectAllocEventCollector collector;
188 size_t size_in_bytes = _allocator._word_size * HeapWordSize;
189 ThreadLocalAllocBuffer& tlab = _thread->tlab();
190
191 if (!_allocated_outside_tlab) {
192 bytes_since_last = tlab.bytes_since_last_sample_point();
193 }
194
195 _thread->heap_sampler().check_for_sampling(obj_h(), size_in_bytes, bytes_since_last);
196 }
197
198 if (_tlab_end_reset_for_sample || _allocated_tlab_size != 0) {
199 // Tell tlab to forget bytes_since_last if we passed it to the heap sampler.
200 _thread->tlab().set_sample_end(bytes_since_last != 0);
201 }
202 }
203
204 void MemAllocator::Allocation::notify_allocation_low_memory_detector() {
205 // support low memory notifications (no-op if not enabled)
206 LowMemoryDetector::detect_low_memory_for_collected_pools();
207 }
208
209 void MemAllocator::Allocation::notify_allocation_jfr_sampler() {
210 HeapWord* mem = cast_from_oop<HeapWord*>(obj());
211 size_t size_in_bytes = _allocator._word_size * HeapWordSize;
212
213 if (_allocated_outside_tlab) {
214 AllocTracer::send_allocation_outside_tlab(obj()->klass(), mem, size_in_bytes, _thread);
215 } else if (_allocated_tlab_size != 0) {
216 // TLAB was refilled
217 AllocTracer::send_allocation_in_new_tlab(obj()->klass(), mem, _allocated_tlab_size * HeapWordSize,
218 size_in_bytes, _thread);
219 }
220 }
221
222 void MemAllocator::Allocation::notify_allocation_dtrace_sampler() {
223 if (DTraceAllocProbes) {
224 // support for Dtrace object alloc event (no-op most of the time)
225 Klass* klass = obj()->klass();
226 size_t word_size = _allocator._word_size;
227 if (klass != nullptr && klass->name() != nullptr) {
228 SharedRuntime::dtrace_object_alloc(_thread, obj(), word_size);
229 }
230 }
231 }
232
233 void MemAllocator::Allocation::notify_allocation() {
234 notify_allocation_low_memory_detector();
235 notify_allocation_jfr_sampler();
236 notify_allocation_dtrace_sampler();
237 notify_allocation_jvmti_sampler();
238 }
239
240 HeapWord* MemAllocator::mem_allocate_outside_tlab(Allocation& allocation) const {
241 allocation._allocated_outside_tlab = true;
242 HeapWord* mem = Universe::heap()->mem_allocate(_word_size, &allocation._overhead_limit_exceeded);
243 if (mem == nullptr) {
244 return mem;
245 }
246
247 size_t size_in_bytes = _word_size * HeapWordSize;
248 _thread->incr_allocated_bytes(size_in_bytes);
249
250 return mem;
251 }
252
253 HeapWord* MemAllocator::mem_allocate_inside_tlab_fast() const {
254 return _thread->tlab().allocate(_word_size);
255 }
256
257 HeapWord* MemAllocator::mem_allocate_inside_tlab_slow(Allocation& allocation) const {
258 HeapWord* mem = nullptr;
259 ThreadLocalAllocBuffer& tlab = _thread->tlab();
260
261 if (JvmtiExport::should_post_sampled_object_alloc()) {
262 tlab.set_back_allocation_end();
263 mem = tlab.allocate(_word_size);
264
265 // We set back the allocation sample point to try to allocate this, reset it
266 // when done.
267 allocation._tlab_end_reset_for_sample = true;
268
269 if (mem != nullptr) {
270 return mem;
271 }
272 }
273
274 // Retain tlab and allocate object in shared space if
275 // the amount free in the tlab is too large to discard.
276 if (tlab.free() > tlab.refill_waste_limit()) {
277 tlab.record_slow_allocation(_word_size);
278 return nullptr;
279 }
280
281 // Discard tlab and allocate a new one.
282 // To minimize fragmentation, the last TLAB may be smaller than the rest.
283 size_t new_tlab_size = tlab.compute_size(_word_size);
284
285 tlab.retire_before_allocation();
286
287 if (new_tlab_size == 0) {
288 return nullptr;
289 }
290
291 // Allocate a new TLAB requesting new_tlab_size. Any size
292 // between minimal and new_tlab_size is accepted.
293 size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size);
294 mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size);
295 if (mem == nullptr) {
296 assert(allocation._allocated_tlab_size == 0,
297 "Allocation failed, but actual size was updated. min: " SIZE_FORMAT
298 ", desired: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
299 min_tlab_size, new_tlab_size, allocation._allocated_tlab_size);
300 return nullptr;
301 }
302 assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: "
303 PTR_FORMAT " min: " SIZE_FORMAT ", desired: " SIZE_FORMAT,
304 p2i(mem), min_tlab_size, new_tlab_size);
305
306 // ...and clear or zap just allocated TLAB, if needed.
307 if (ZeroTLAB) {
308 Copy::zero_to_words(mem, allocation._allocated_tlab_size);
309 } else if (ZapTLAB) {
310 // Skip mangling the space corresponding to the object header to
311 // ensure that the returned space is not considered parsable by
312 // any concurrent GC thread.
313 size_t hdr_size = oopDesc::header_size();
314 Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal);
315 }
316
317 tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size);
318 return mem;
319 }
320
321 HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const {
322 if (UseTLAB) {
323 // Try allocating from an existing TLAB.
324 HeapWord* mem = mem_allocate_inside_tlab_fast();
325 if (mem != nullptr) {
326 return mem;
327 }
328 }
329
330 // Allocation of an oop can always invoke a safepoint.
331 debug_only(allocation._thread->check_for_valid_safepoint_state());
332
333 if (UseTLAB) {
334 // Try refilling the TLAB and allocating the object in it.
335 HeapWord* mem = mem_allocate_inside_tlab_slow(allocation);
336 if (mem != nullptr) {
337 return mem;
338 }
339 }
340
341 return mem_allocate_outside_tlab(allocation);
342 }
343
344 oop MemAllocator::allocate() const {
345 oop obj = nullptr;
346 {
347 Allocation allocation(*this, &obj);
348 HeapWord* mem = mem_allocate(allocation);
349 if (mem != nullptr) {
350 obj = initialize(mem);
351 } else {
352 // The unhandled oop detector will poison local variable obj,
353 // so reset it to null if mem is null.
354 obj = nullptr;
355 }
356 }
357 return obj;
358 }
359
360 void MemAllocator::mem_clear(HeapWord* mem) const {
361 assert(mem != nullptr, "cannot initialize null object");
362 const size_t hs = oopDesc::header_size();
363 assert(_word_size >= hs, "unexpected object size");
364 oopDesc::set_klass_gap(mem, 0);
365 Copy::fill_to_aligned_words(mem + hs, _word_size - hs);
366 }
367
368 oop MemAllocator::finish(HeapWord* mem) const {
369 assert(mem != nullptr, "null object pointer");
370 oopDesc::set_mark(mem, Klass::default_prototype_header(_klass));
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 oopDesc::release_set_klass(mem, _klass);
375 return cast_to_oop(mem);
376 }
377
378 oop ObjAllocator::initialize(HeapWord* mem) const {
379 mem_clear(mem);
380 return finish(mem);
381 }
382
383 oop ObjBufferAllocator::initialize(HeapWord* mem) const {
384 oopDesc::set_klass_gap(mem, 0);
385 return finish(mem);
386 }
387
388
389 oop ObjArrayAllocator::initialize(HeapWord* mem) const {
390 // Set array length before setting the _klass field because a
391 // non-null klass field indicates that the object is parsable by
392 // concurrent GC.
393 assert(_length >= 0, "length should be non-negative");
394 if (_do_zero) {
395 mem_clear(mem);
396 mem_zap_start_padding(mem);
397 mem_zap_end_padding(mem);
398 }
399 arrayOopDesc::set_length(mem, _length);
400 return finish(mem);
401 }
402
403 #ifndef PRODUCT
404 void ObjArrayAllocator::mem_zap_start_padding(HeapWord* mem) const {
405 const BasicType element_type = ArrayKlass::cast(_klass)->element_type();
406 const size_t base_offset_in_bytes = arrayOopDesc::base_offset_in_bytes(element_type);
407 const size_t header_size_in_bytes = arrayOopDesc::header_size_in_bytes();
408
409 const address base = reinterpret_cast<address>(mem) + base_offset_in_bytes;
410 const address header_end = reinterpret_cast<address>(mem) + header_size_in_bytes;
411
412 if (header_end < base) {
413 const size_t padding_in_bytes = base - header_end;
414 Copy::fill_to_bytes(header_end, padding_in_bytes, heapPaddingByteVal);
415 }
416 }
417
418 void ObjArrayAllocator::mem_zap_end_padding(HeapWord* mem) const {
419 const size_t length_in_bytes = static_cast<size_t>(_length) << ArrayKlass::cast(_klass)->log2_element_size();
420 const BasicType element_type = ArrayKlass::cast(_klass)->element_type();
421 const size_t base_offset_in_bytes = arrayOopDesc::base_offset_in_bytes(element_type);
422 const size_t size_in_bytes = _word_size * BytesPerWord;
423
424 const address obj_end = reinterpret_cast<address>(mem) + size_in_bytes;
425 const address base = reinterpret_cast<address>(mem) + base_offset_in_bytes;
426 const address elements_end = base + length_in_bytes;
427 assert(elements_end <= obj_end, "payload must fit in object");
428 if (elements_end < obj_end) {
429 const size_t padding_in_bytes = obj_end - elements_end;
430 Copy::fill_to_bytes(elements_end, padding_in_bytes, heapPaddingByteVal);
431 }
432 }
433 #endif
434
435 oop ClassAllocator::initialize(HeapWord* mem) const {
436 // Set oop_size field before setting the _klass field because a
437 // non-null _klass field indicates that the object is parsable by
438 // concurrent GC.
439 assert(_word_size > 0, "oop_size must be positive.");
440 mem_clear(mem);
441 java_lang_Class::set_oop_size(mem, _word_size);
442 return finish(mem);
443 }