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 }