1 /*
  2  * Copyright (c) 2018, 2021, 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 "gc/shared/allocTracer.hpp"
 28 #include "gc/shared/collectedHeap.hpp"
 29 #include "gc/shared/memAllocator.hpp"
 30 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
 31 #include "gc/shared/tlab_globals.hpp"
 32 #include "memory/universe.hpp"
 33 #include "oops/arrayOop.hpp"
 34 #include "oops/oop.inline.hpp"
 35 #include "prims/jvmtiExport.hpp"
 36 #include "runtime/sharedRuntime.hpp"
 37 #include "runtime/handles.inline.hpp"
 38 #include "runtime/thread.inline.hpp"
 39 #include "services/lowMemoryDetector.hpp"
 40 #include "utilities/align.hpp"
 41 #include "utilities/copy.hpp"
 42 
 43 class MemAllocator::Allocation: StackObj {
 44   friend class MemAllocator;
 45 
 46   const MemAllocator& _allocator;
 47   JavaThread*         _thread;
 48   oop*                _obj_ptr;
 49   bool                _overhead_limit_exceeded;
 50   bool                _allocated_outside_tlab;
 51   size_t              _allocated_tlab_size;
 52   bool                _tlab_end_reset_for_sample;
 53 
 54   bool check_out_of_memory();
 55   void verify_before();
 56   void verify_after();
 57   void notify_allocation();
 58   void notify_allocation_jvmti_sampler();
 59   void notify_allocation_low_memory_detector();
 60   void notify_allocation_jfr_sampler();
 61   void notify_allocation_dtrace_sampler();
 62   void check_for_bad_heap_word_value() const;
 63 #ifdef ASSERT
 64   void check_for_valid_allocation_state() const;
 65 #endif
 66 
 67   class PreserveObj;
 68 
 69 public:
 70   Allocation(const MemAllocator& allocator, oop* obj_ptr)
 71     : _allocator(allocator),
 72       _thread(JavaThread::current()),
 73       _obj_ptr(obj_ptr),
 74       _overhead_limit_exceeded(false),
 75       _allocated_outside_tlab(false),
 76       _allocated_tlab_size(0),
 77       _tlab_end_reset_for_sample(false)
 78   {
 79     verify_before();
 80   }
 81 
 82   ~Allocation() {
 83     if (!check_out_of_memory()) {
 84       verify_after();
 85       notify_allocation();
 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 = NULL;
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() != NULL) {
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 void MemAllocator::Allocation::verify_after() {
152   NOT_PRODUCT(check_for_bad_heap_word_value();)
153 }
154 
155 void MemAllocator::Allocation::check_for_bad_heap_word_value() const {
156   MemRegion obj_range = _allocator.obj_memory_range(obj());
157   HeapWord* addr = obj_range.start();
158   size_t size = obj_range.word_size();
159   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
160     for (size_t slot = 0; slot < size; slot += 1) {
161       assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
162              "Found badHeapWordValue in post-allocation check");
163     }
164   }
165 }
166 
167 #ifdef ASSERT
168 void MemAllocator::Allocation::check_for_valid_allocation_state() const {
169   // How to choose between a pending exception and a potential
170   // OutOfMemoryError?  Don't allow pending exceptions.
171   // This is a VM policy failure, so how do we exhaustively test it?
172   assert(!_thread->has_pending_exception(),
173          "shouldn't be allocating with pending exception");
174   // Allocation of an oop can always invoke a safepoint.
175   JavaThread::cast(_thread)->check_for_valid_safepoint_state();
176 }
177 #endif
178 
179 void MemAllocator::Allocation::notify_allocation_jvmti_sampler() {
180   // support for JVMTI VMObjectAlloc event (no-op if not enabled)
181   JvmtiExport::vm_object_alloc_event_collector(obj());
182 
183   if (!JvmtiExport::should_post_sampled_object_alloc()) {
184     // Sampling disabled
185     return;
186   }
187 
188   if (!_allocated_outside_tlab && _allocated_tlab_size == 0 && !_tlab_end_reset_for_sample) {
189     // Sample if it's a non-TLAB allocation, or a TLAB allocation that either refills the TLAB
190     // or expands it due to taking a sampler induced slow path.
191     return;
192   }
193 
194   // If we want to be sampling, protect the allocated object with a Handle
195   // before doing the callback. The callback is done in the destructor of
196   // the JvmtiSampledObjectAllocEventCollector.
197   size_t bytes_since_last = 0;
198 
199   {
200     PreserveObj obj_h(_thread, _obj_ptr);
201     JvmtiSampledObjectAllocEventCollector collector;
202     size_t size_in_bytes = _allocator._word_size * HeapWordSize;
203     ThreadLocalAllocBuffer& tlab = _thread->tlab();
204 
205     if (!_allocated_outside_tlab) {
206       bytes_since_last = tlab.bytes_since_last_sample_point();
207     }
208 
209     _thread->heap_sampler().check_for_sampling(obj_h(), size_in_bytes, bytes_since_last);
210   }
211 
212   if (_tlab_end_reset_for_sample || _allocated_tlab_size != 0) {
213     // Tell tlab to forget bytes_since_last if we passed it to the heap sampler.
214     _thread->tlab().set_sample_end(bytes_since_last != 0);
215   }
216 }
217 
218 void MemAllocator::Allocation::notify_allocation_low_memory_detector() {
219   // support low memory notifications (no-op if not enabled)
220   LowMemoryDetector::detect_low_memory_for_collected_pools();
221 }
222 
223 void MemAllocator::Allocation::notify_allocation_jfr_sampler() {
224   HeapWord* mem = cast_from_oop<HeapWord*>(obj());
225   size_t size_in_bytes = _allocator._word_size * HeapWordSize;
226 
227   if (_allocated_outside_tlab) {
228     AllocTracer::send_allocation_outside_tlab(obj()->klass(), mem, size_in_bytes, _thread);
229   } else if (_allocated_tlab_size != 0) {
230     // TLAB was refilled
231     AllocTracer::send_allocation_in_new_tlab(obj()->klass(), mem, _allocated_tlab_size * HeapWordSize,
232                                              size_in_bytes, _thread);
233   }
234 }
235 
236 void MemAllocator::Allocation::notify_allocation_dtrace_sampler() {
237   if (DTraceAllocProbes) {
238     // support for Dtrace object alloc event (no-op most of the time)
239     Klass* klass = obj()->klass();
240     size_t word_size = _allocator._word_size;
241     if (klass != NULL && klass->name() != NULL) {
242       SharedRuntime::dtrace_object_alloc(Thread::current(), obj(), word_size);
243     }
244   }
245 }
246 
247 void MemAllocator::Allocation::notify_allocation() {
248   notify_allocation_low_memory_detector();
249   notify_allocation_jfr_sampler();
250   notify_allocation_dtrace_sampler();
251   notify_allocation_jvmti_sampler();
252 }
253 
254 HeapWord* MemAllocator::allocate_outside_tlab(Allocation& allocation) const {
255   allocation._allocated_outside_tlab = true;
256   HeapWord* mem = Universe::heap()->mem_allocate(_word_size, &allocation._overhead_limit_exceeded);
257   if (mem == NULL) {
258     return mem;
259   }
260 
261   NOT_PRODUCT(Universe::heap()->check_for_non_bad_heap_word_value(mem, _word_size));
262   size_t size_in_bytes = _word_size * HeapWordSize;
263   _thread->incr_allocated_bytes(size_in_bytes);
264 
265   return mem;
266 }
267 
268 HeapWord* MemAllocator::allocate_inside_tlab(Allocation& allocation) const {
269   assert(UseTLAB, "should use UseTLAB");
270 
271   // Try allocating from an existing TLAB.
272   HeapWord* mem = _thread->tlab().allocate(_word_size);
273   if (mem != NULL) {
274     return mem;
275   }
276 
277   // Try refilling the TLAB and allocating the object in it.
278   return allocate_inside_tlab_slow(allocation);
279 }
280 
281 HeapWord* MemAllocator::allocate_inside_tlab_slow(Allocation& allocation) const {
282   HeapWord* mem = NULL;
283   ThreadLocalAllocBuffer& tlab = _thread->tlab();
284 
285   if (JvmtiExport::should_post_sampled_object_alloc()) {
286     tlab.set_back_allocation_end();
287     mem = tlab.allocate(_word_size);
288 
289     // We set back the allocation sample point to try to allocate this, reset it
290     // when done.
291     allocation._tlab_end_reset_for_sample = true;
292 
293     if (mem != NULL) {
294       return mem;
295     }
296   }
297 
298   // Retain tlab and allocate object in shared space if
299   // the amount free in the tlab is too large to discard.
300   if (tlab.free() > tlab.refill_waste_limit()) {
301     tlab.record_slow_allocation(_word_size);
302     return NULL;
303   }
304 
305   // Discard tlab and allocate a new one.
306   // To minimize fragmentation, the last TLAB may be smaller than the rest.
307   size_t new_tlab_size = tlab.compute_size(_word_size);
308 
309   tlab.retire_before_allocation();
310 
311   if (new_tlab_size == 0) {
312     return NULL;
313   }
314 
315   // Allocate a new TLAB requesting new_tlab_size. Any size
316   // between minimal and new_tlab_size is accepted.
317   size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size);
318   mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size);
319   if (mem == NULL) {
320     assert(allocation._allocated_tlab_size == 0,
321            "Allocation failed, but actual size was updated. min: " SIZE_FORMAT
322            ", desired: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
323            min_tlab_size, new_tlab_size, allocation._allocated_tlab_size);
324     return NULL;
325   }
326   assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: "
327          PTR_FORMAT " min: " SIZE_FORMAT ", desired: " SIZE_FORMAT,
328          p2i(mem), min_tlab_size, new_tlab_size);
329 
330   if (ZeroTLAB) {
331     // ..and clear it.
332     Copy::zero_to_words(mem, allocation._allocated_tlab_size);
333   } else {
334     // ...and zap just allocated object.
335 #ifdef ASSERT
336     // Skip mangling the space corresponding to the object header to
337     // ensure that the returned space is not considered parsable by
338     // any concurrent GC thread.
339     size_t hdr_size = oopDesc::header_size();
340     Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal);
341 #endif // ASSERT
342   }
343 
344   tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size);
345   return mem;
346 }
347 
348 HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const {
349   if (UseTLAB) {
350     HeapWord* result = allocate_inside_tlab(allocation);
351     if (result != NULL) {
352       return result;
353     }
354   }
355 
356   return allocate_outside_tlab(allocation);
357 }
358 
359 oop MemAllocator::allocate() const {
360   oop obj = NULL;
361   {
362     Allocation allocation(*this, &obj);
363     HeapWord* mem = mem_allocate(allocation);
364     if (mem != NULL) {
365       obj = initialize(mem);
366     } else {
367       // The unhandled oop detector will poison local variable obj,
368       // so reset it to NULL if mem is NULL.
369       obj = NULL;
370     }
371   }
372   return obj;
373 }
374 
375 void MemAllocator::mem_clear(HeapWord* mem) const {
376   assert(mem != NULL, "cannot initialize NULL object");
377   const size_t hs = oopDesc::header_size();
378   assert(_word_size >= hs, "unexpected object size");
379   oopDesc::set_klass_gap(mem, 0);
380   Copy::fill_to_aligned_words(mem + hs, _word_size - hs);
381 }
382 
383 oop MemAllocator::finish(HeapWord* mem) const {
384   assert(mem != NULL, "NULL object pointer");
385   // May be bootstrapping
386   oopDesc::set_mark(mem, markWord::prototype());
387   // Need a release store to ensure array/class length, mark word, and
388   // object zeroing are visible before setting the klass non-NULL, for
389   // concurrent collectors.
390   oopDesc::release_set_klass(mem, _klass);
391   return cast_to_oop(mem);
392 }
393 
394 oop ObjAllocator::initialize(HeapWord* mem) const {
395   mem_clear(mem);
396   return finish(mem);
397 }
398 
399 MemRegion ObjArrayAllocator::obj_memory_range(oop obj) const {
400   if (_do_zero) {
401     return MemAllocator::obj_memory_range(obj);
402   }
403   ArrayKlass* array_klass = ArrayKlass::cast(_klass);
404   const size_t hs = arrayOopDesc::header_size(array_klass->element_type());
405   return MemRegion(cast_from_oop<HeapWord*>(obj) + hs, _word_size - hs);
406 }
407 
408 oop ObjArrayAllocator::initialize(HeapWord* mem) const {
409   // Set array length before setting the _klass field because a
410   // non-NULL klass field indicates that the object is parsable by
411   // concurrent GC.
412   assert(_length >= 0, "length should be non-negative");
413   if (_do_zero) {
414     mem_clear(mem);
415   }
416   arrayOopDesc::set_length(mem, _length);
417   return finish(mem);
418 }
419 
420 oop ClassAllocator::initialize(HeapWord* mem) const {
421   // Set oop_size field before setting the _klass field because a
422   // non-NULL _klass field indicates that the object is parsable by
423   // concurrent GC.
424   assert(_word_size > 0, "oop_size must be positive.");
425   mem_clear(mem);
426   java_lang_Class::set_oop_size(mem, _word_size);
427   return finish(mem);
428 }