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 void check_for_bad_heap_word_value() const;
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::current()),
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 verify_before();
82 }
83
84 ~Allocation() {
85 if (!check_out_of_memory()) {
86 verify_after();
87 notify_allocation(_thread);
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->in_retryable_allocation()) {
127 // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError support
128 report_java_out_of_memory(message);
129
130 if (JvmtiExport::should_post_resource_exhausted()) {
131 JvmtiExport::post_resource_exhausted(
132 JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR | JVMTI_RESOURCE_EXHAUSTED_JAVA_HEAP,
133 message);
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_retry(), 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_gc_active(), "Allocation during gc not allowed");
151 }
152
153 void MemAllocator::Allocation::verify_after() {
154 NOT_PRODUCT(check_for_bad_heap_word_value();)
155 }
156
157 void MemAllocator::Allocation::check_for_bad_heap_word_value() const {
158 MemRegion obj_range = _allocator.obj_memory_range(obj());
159 HeapWord* addr = obj_range.start();
160 size_t size = obj_range.word_size();
161 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
162 for (size_t slot = 0; slot < size; slot += 1) {
163 assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
164 "Found badHeapWordValue in post-allocation check");
165 }
166 }
167 }
168
169 #ifdef ASSERT
170 void MemAllocator::Allocation::check_for_valid_allocation_state() const {
171 // How to choose between a pending exception and a potential
172 // OutOfMemoryError? Don't allow pending exceptions.
173 // This is a VM policy failure, so how do we exhaustively test it?
174 assert(!_thread->has_pending_exception(),
175 "shouldn't be allocating with pending exception");
176 // Allocation of an oop can always invoke a safepoint.
177 JavaThread::cast(_thread)->check_for_valid_safepoint_state();
178 }
179 #endif
180
181 void MemAllocator::Allocation::notify_allocation_jvmti_sampler() {
182 // support for JVMTI VMObjectAlloc event (no-op if not enabled)
183 JvmtiExport::vm_object_alloc_event_collector(obj());
184
185 if (!JvmtiExport::should_post_sampled_object_alloc()) {
186 // Sampling disabled
187 return;
188 }
189
190 if (!_allocated_outside_tlab && _allocated_tlab_size == 0 && !_tlab_end_reset_for_sample) {
191 // Sample if it's a non-TLAB allocation, or a TLAB allocation that either refills the TLAB
192 // or expands it due to taking a sampler induced slow path.
193 return;
194 }
195
196 // If we want to be sampling, protect the allocated object with a Handle
197 // before doing the callback. The callback is done in the destructor of
198 // the JvmtiSampledObjectAllocEventCollector.
199 size_t bytes_since_last = 0;
200
201 {
202 PreserveObj obj_h(_thread, _obj_ptr);
203 JvmtiSampledObjectAllocEventCollector collector;
204 size_t size_in_bytes = _allocator._word_size * HeapWordSize;
205 ThreadLocalAllocBuffer& tlab = _thread->tlab();
206
207 if (!_allocated_outside_tlab) {
208 bytes_since_last = tlab.bytes_since_last_sample_point();
209 }
210
211 _thread->heap_sampler().check_for_sampling(obj_h(), size_in_bytes, bytes_since_last);
212 }
213
214 if (_tlab_end_reset_for_sample || _allocated_tlab_size != 0) {
215 // Tell tlab to forget bytes_since_last if we passed it to the heap sampler.
216 _thread->tlab().set_sample_end(bytes_since_last != 0);
217 }
218 }
219
220 void MemAllocator::Allocation::notify_allocation_low_memory_detector() {
221 // support low memory notifications (no-op if not enabled)
222 LowMemoryDetector::detect_low_memory_for_collected_pools();
223 }
224
225 void MemAllocator::Allocation::notify_allocation_jfr_sampler() {
226 HeapWord* mem = cast_from_oop<HeapWord*>(obj());
227 size_t size_in_bytes = _allocator._word_size * HeapWordSize;
228
229 if (_allocated_outside_tlab) {
230 AllocTracer::send_allocation_outside_tlab(obj()->klass(), mem, size_in_bytes, _thread);
231 } else if (_allocated_tlab_size != 0) {
232 // TLAB was refilled
233 AllocTracer::send_allocation_in_new_tlab(obj()->klass(), mem, _allocated_tlab_size * HeapWordSize,
234 size_in_bytes, _thread);
235 }
236 }
237
238 void MemAllocator::Allocation::notify_allocation_dtrace_sampler(JavaThread* thread) {
239 if (DTraceAllocProbes) {
240 // support for Dtrace object alloc event (no-op most of the time)
241 Klass* klass = obj()->klass();
242 size_t word_size = _allocator._word_size;
243 if (klass != nullptr && klass->name() != nullptr) {
244 SharedRuntime::dtrace_object_alloc(thread, obj(), word_size);
245 }
246 }
247 }
248
249 void MemAllocator::Allocation::notify_allocation(JavaThread* thread) {
250 notify_allocation_low_memory_detector();
251 notify_allocation_jfr_sampler();
252 notify_allocation_dtrace_sampler(thread);
253 notify_allocation_jvmti_sampler();
254 }
255
256 HeapWord* MemAllocator::mem_allocate_outside_tlab(Allocation& allocation) const {
257 allocation._allocated_outside_tlab = true;
258 HeapWord* mem = Universe::heap()->mem_allocate(_word_size, &allocation._overhead_limit_exceeded);
259 if (mem == nullptr) {
260 return mem;
261 }
262
263 NOT_PRODUCT(Universe::heap()->check_for_non_bad_heap_word_value(mem, _word_size));
264 size_t size_in_bytes = _word_size * HeapWordSize;
265 _thread->incr_allocated_bytes(size_in_bytes);
266
267 return mem;
268 }
269
270 HeapWord* MemAllocator::mem_allocate_inside_tlab(Allocation& allocation) const {
271 assert(UseTLAB, "should use UseTLAB");
272
273 // Try allocating from an existing TLAB.
274 HeapWord* mem = mem_allocate_inside_tlab_fast();
275 if (mem != nullptr) {
276 return mem;
277 }
278
279 // Try refilling the TLAB and allocating the object in it.
280 return mem_allocate_inside_tlab_slow(allocation);
281 }
282
283 HeapWord* MemAllocator::mem_allocate_inside_tlab_fast() const {
284 return _thread->tlab().allocate(_word_size);
285 }
286
287 HeapWord* MemAllocator::mem_allocate_inside_tlab_slow(Allocation& allocation) const {
288 HeapWord* mem = nullptr;
289 ThreadLocalAllocBuffer& tlab = _thread->tlab();
290
291 if (JvmtiExport::should_post_sampled_object_alloc()) {
292 tlab.set_back_allocation_end();
293 mem = tlab.allocate(_word_size);
294
295 // We set back the allocation sample point to try to allocate this, reset it
296 // when done.
297 allocation._tlab_end_reset_for_sample = true;
298
299 if (mem != nullptr) {
300 return mem;
301 }
302 }
303
304 // Retain tlab and allocate object in shared space if
305 // the amount free in the tlab is too large to discard.
306 if (tlab.free() > tlab.refill_waste_limit()) {
307 tlab.record_slow_allocation(_word_size);
308 return nullptr;
309 }
310
311 // Discard tlab and allocate a new one.
312 // To minimize fragmentation, the last TLAB may be smaller than the rest.
313 size_t new_tlab_size = tlab.compute_size(_word_size);
314
315 tlab.retire_before_allocation();
316
317 if (new_tlab_size == 0) {
318 return nullptr;
319 }
320
321 // Allocate a new TLAB requesting new_tlab_size. Any size
322 // between minimal and new_tlab_size is accepted.
323 size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size);
324 mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size);
325 if (mem == nullptr) {
326 assert(allocation._allocated_tlab_size == 0,
327 "Allocation failed, but actual size was updated. min: " SIZE_FORMAT
328 ", desired: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
329 min_tlab_size, new_tlab_size, allocation._allocated_tlab_size);
330 return nullptr;
331 }
332 assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: "
333 PTR_FORMAT " min: " SIZE_FORMAT ", desired: " SIZE_FORMAT,
334 p2i(mem), min_tlab_size, new_tlab_size);
335
336 if (ZeroTLAB) {
337 // ..and clear it.
338 Copy::zero_to_words(mem, allocation._allocated_tlab_size);
339 } else {
340 // ...and zap just allocated object.
341 #ifdef ASSERT
342 // Skip mangling the space corresponding to the object header to
343 // ensure that the returned space is not considered parsable by
344 // any concurrent GC thread.
345 size_t hdr_size = oopDesc::header_size();
346 Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal);
347 #endif // ASSERT
348 }
349
350 tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size);
351 return mem;
352 }
353
354
355 HeapWord* MemAllocator::mem_allocate_slow(Allocation& allocation) const {
356 // Allocation of an oop can always invoke a safepoint.
357 debug_only(JavaThread::cast(_thread)->check_for_valid_safepoint_state());
358
359 if (UseTLAB) {
360 // Try refilling the TLAB and allocating the object in it.
361 HeapWord* mem = mem_allocate_inside_tlab_slow(allocation);
362 if (mem != nullptr) {
363 return mem;
364 }
365 }
366
367 return mem_allocate_outside_tlab(allocation);
368 }
369
370 HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const {
371 if (UseTLAB) {
372 // Try allocating from an existing TLAB.
373 HeapWord* mem = mem_allocate_inside_tlab_fast();
374 if (mem != nullptr) {
375 return mem;
376 }
377 }
378
379 return mem_allocate_slow(allocation);
380 }
381
382 oop MemAllocator::allocate() const {
383 oop obj = nullptr;
384 {
385 Allocation allocation(*this, &obj);
386 HeapWord* mem = mem_allocate(allocation);
387 if (mem != nullptr) {
388 obj = initialize(mem);
389 } else {
390 // The unhandled oop detector will poison local variable obj,
391 // so reset it to null if mem is null.
392 obj = nullptr;
393 }
394 }
395 return obj;
396 }
397
398 void MemAllocator::mem_clear(HeapWord* mem) const {
399 assert(mem != nullptr, "cannot initialize null object");
400 const size_t hs = oopDesc::header_size();
401 assert(_word_size >= hs, "unexpected object size");
402 if (!UseCompactObjectHeaders) {
403 oopDesc::set_klass_gap(mem, 0);
404 }
405 Copy::fill_to_aligned_words(mem + hs, _word_size - hs);
406 }
407
408 oop MemAllocator::finish(HeapWord* mem) const {
409 assert(mem != nullptr, "null object pointer");
410 // Need a release store to ensure array/class length, mark word, and
411 // object zeroing are visible before setting the klass non-null, for
412 // concurrent collectors.
413 if (UseCompactObjectHeaders) {
414 oopDesc::release_set_mark(mem, _klass->prototype_header());
415 } else {
416 oopDesc::set_mark(mem, markWord::prototype());
417 oopDesc::release_set_klass(mem, _klass);
418 }
419 return cast_to_oop(mem);
420 }
421
422 oop ObjAllocator::initialize(HeapWord* mem) const {
423 mem_clear(mem);
424 return finish(mem);
425 }
426
427 MemRegion ObjArrayAllocator::obj_memory_range(oop obj) const {
428 if (_do_zero) {
429 return MemAllocator::obj_memory_range(obj);
430 }
431 ArrayKlass* array_klass = ArrayKlass::cast(_klass);
432 const size_t hs = align_up(arrayOopDesc::base_offset_in_bytes(array_klass->element_type()), HeapWordSize) / HeapWordSize;
433 return MemRegion(cast_from_oop<HeapWord*>(obj) + hs, _word_size - hs);
434 }
435
436 oop ObjArrayAllocator::initialize(HeapWord* mem) const {
437 // Set array length before setting the _klass field because a
438 // non-null klass field indicates that the object is parsable by
439 // concurrent GC.
440 assert(_length >= 0, "length should be non-negative");
441 if (_do_zero) {
442 mem_clear(mem);
443 }
444 arrayOopDesc::set_length(mem, _length);
445 return finish(mem);
446 }
447
448 oop ClassAllocator::initialize(HeapWord* mem) const {
449 // Set oop_size field before setting the _klass field because a
450 // non-null _klass field indicates that the object is parsable by
451 // concurrent GC.
452 assert(_word_size > 0, "oop_size must be positive.");
453 mem_clear(mem);
454 java_lang_Class::set_oop_size(mem, _word_size);
455 return finish(mem);
456 }