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();
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->in_retryable_allocation()) {
126 // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError support
127 report_java_out_of_memory(message);
128
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 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_retry(), 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_gc_active(), "Allocation during gc 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(Allocation& allocation) const {
253 assert(UseTLAB, "should use UseTLAB");
254
255 // Try allocating from an existing TLAB.
256 HeapWord* mem = mem_allocate_inside_tlab_fast();
257 if (mem != nullptr) {
258 return mem;
259 }
260
261 // Try refilling the TLAB and allocating the object in it.
262 return mem_allocate_inside_tlab_slow(allocation);
263 }
264
265 HeapWord* MemAllocator::mem_allocate_inside_tlab_fast() const {
266 return _thread->tlab().allocate(_word_size);
267 }
268
269 HeapWord* MemAllocator::mem_allocate_inside_tlab_slow(Allocation& allocation) const {
270 HeapWord* mem = nullptr;
271 ThreadLocalAllocBuffer& tlab = _thread->tlab();
272
273 if (JvmtiExport::should_post_sampled_object_alloc()) {
274 tlab.set_back_allocation_end();
275 mem = tlab.allocate(_word_size);
276
277 // We set back the allocation sample point to try to allocate this, reset it
278 // when done.
279 allocation._tlab_end_reset_for_sample = true;
280
281 if (mem != nullptr) {
282 return mem;
283 }
284 }
285
286 // Retain tlab and allocate object in shared space if
287 // the amount free in the tlab is too large to discard.
288 if (tlab.free() > tlab.refill_waste_limit()) {
289 tlab.record_slow_allocation(_word_size);
290 return nullptr;
291 }
292
293 // Discard tlab and allocate a new one.
294 // To minimize fragmentation, the last TLAB may be smaller than the rest.
295 size_t new_tlab_size = tlab.compute_size(_word_size);
296
297 tlab.retire_before_allocation();
298
299 if (new_tlab_size == 0) {
300 return nullptr;
301 }
302
303 // Allocate a new TLAB requesting new_tlab_size. Any size
304 // between minimal and new_tlab_size is accepted.
305 size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size);
306 mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size);
307 if (mem == nullptr) {
308 assert(allocation._allocated_tlab_size == 0,
309 "Allocation failed, but actual size was updated. min: " SIZE_FORMAT
310 ", desired: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
311 min_tlab_size, new_tlab_size, allocation._allocated_tlab_size);
312 return nullptr;
313 }
314 assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: "
315 PTR_FORMAT " min: " SIZE_FORMAT ", desired: " SIZE_FORMAT,
316 p2i(mem), min_tlab_size, new_tlab_size);
317
318 if (ZeroTLAB) {
319 // ..and clear it.
320 Copy::zero_to_words(mem, allocation._allocated_tlab_size);
321 } else {
322 // ...and zap just allocated object.
323 #ifdef ASSERT
324 // Skip mangling the space corresponding to the object header to
325 // ensure that the returned space is not considered parsable by
326 // any concurrent GC thread.
327 size_t hdr_size = oopDesc::header_size();
328 Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal);
329 #endif // ASSERT
330 }
331
332 tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size);
333 return mem;
334 }
335
336
337 HeapWord* MemAllocator::mem_allocate_slow(Allocation& allocation) const {
338 // Allocation of an oop can always invoke a safepoint.
339 debug_only(allocation._thread->check_for_valid_safepoint_state());
340
341 if (UseTLAB) {
342 // Try refilling the TLAB and allocating the object in it.
343 HeapWord* mem = mem_allocate_inside_tlab_slow(allocation);
344 if (mem != nullptr) {
345 return mem;
346 }
347 }
348
349 return mem_allocate_outside_tlab(allocation);
350 }
351
352 HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const {
353 if (UseTLAB) {
354 // Try allocating from an existing TLAB.
355 HeapWord* mem = mem_allocate_inside_tlab_fast();
356 if (mem != nullptr) {
357 return mem;
358 }
359 }
360
361 return mem_allocate_slow(allocation);
362 }
363
364 oop MemAllocator::allocate() const {
365 oop obj = nullptr;
366 {
367 Allocation allocation(*this, &obj);
368 HeapWord* mem = mem_allocate(allocation);
369 if (mem != nullptr) {
370 obj = initialize(mem);
371 } else {
372 // The unhandled oop detector will poison local variable obj,
373 // so reset it to null if mem is null.
374 obj = nullptr;
375 }
376 }
377 return obj;
378 }
379
380 void MemAllocator::mem_clear(HeapWord* mem) const {
381 assert(mem != nullptr, "cannot initialize null object");
382 const size_t hs = oopDesc::header_size();
383 assert(_word_size >= hs, "unexpected object size");
384 oopDesc::set_klass_gap(mem, 0);
385 Copy::fill_to_aligned_words(mem + hs, _word_size - hs);
386 }
387
388 oop MemAllocator::finish(HeapWord* mem) const {
389 assert(mem != nullptr, "null object pointer");
390 // May be bootstrapping
391 oopDesc::set_mark(mem, markWord::prototype());
392 // Need a release store to ensure array/class length, mark word, and
393 // object zeroing are visible before setting the klass non-null, for
394 // concurrent collectors.
395 oopDesc::release_set_klass(mem, _klass);
396 return cast_to_oop(mem);
397 }
398
399 oop ObjAllocator::initialize(HeapWord* mem) const {
400 mem_clear(mem);
401 return finish(mem);
402 }
403
404 oop ObjArrayAllocator::initialize(HeapWord* mem) const {
405 // Set array length before setting the _klass field because a
406 // non-null klass field indicates that the object is parsable by
407 // concurrent GC.
408 assert(_length >= 0, "length should be non-negative");
409 if (_do_zero) {
410 mem_clear(mem);
411 }
412 arrayOopDesc::set_length(mem, _length);
413 return finish(mem);
414 }
415
416 oop ClassAllocator::initialize(HeapWord* mem) const {
417 // Set oop_size field before setting the _klass field because a
418 // non-null _klass field indicates that the object is parsable by
419 // concurrent GC.
420 assert(_word_size > 0, "oop_size must be positive.");
421 mem_clear(mem);
422 java_lang_Class::set_oop_size(mem, _word_size);
423 return finish(mem);
424 }