Quelle memAllocator.cpp Sprache: C

/*
* Copyright (c) 2018, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/

#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/vmClasses.hpp"
#include "gc/shared/allocTracer.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/memAllocator.hpp"
#include "gc/shared/threadLocalAllocBuffer.inline.hpp"
#include "gc/shared/tlab_globals.hpp"
#include "memory/universe.hpp"
#include "oops/arrayOop.hpp"
#include "oops/oop.inline.hpp"
#include "prims/jvmtiExport.hpp"
#include "runtime/continuationJavaClasses.inline.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/javaThread.hpp"
#include "services/lowMemoryDetector.hpp"
#include "utilities/align.hpp"
#include "utilities/copy.hpp"

class MemAllocator::Allocation: StackObj {
  friend class MemAllocator;

  const MemAllocator& _allocator;
  JavaThread*         _thread;
  oop*                _obj_ptr;
  bool                _overhead_limit_exceeded;
  bool                _allocated_outside_tlab;
  size_t              _allocated_tlab_size;
  bool                _tlab_end_reset_for_sample;

  bool check_out_of_memory();
  void verify_before();
  void verify_after();
  void notify_allocation(JavaThread* thread);
  void notify_allocation_jvmti_sampler();
  void notify_allocation_low_memory_detector();
  void notify_allocation_jfr_sampler();
  void notify_allocation_dtrace_sampler(JavaThread* thread);
  void check_for_bad_heap_word_value() const;
#ifdef ASSERT
  void check_for_valid_allocation_state() const;
#endif

  class PreserveObj;

public:
  Allocation(const MemAllocator& allocator, oop* obj_ptr)
    : _allocator(allocator),
      _thread(JavaThread::current()),
      _obj_ptr(obj_ptr),
      _overhead_limit_exceeded(false),
      _allocated_outside_tlab(false),
      _allocated_tlab_size(0),
      _tlab_end_reset_for_sample(false)
  {
    verify_before();
  }

  ~Allocation() {
    if (!check_out_of_memory()) {
      verify_after();
      notify_allocation(_thread);
    }
  }

  oop obj() const { return *_obj_ptr; }
};

class MemAllocator::Allocation::PreserveObj: StackObj {
  HandleMark _handle_mark;
  Handle     _handle;
  oop* const _obj_ptr;

public:
  PreserveObj(JavaThread* thread, oop* obj_ptr)
    : _handle_mark(thread),
      _handle(thread, *obj_ptr),
      _obj_ptr(obj_ptr)
  {
    *obj_ptr = NULL;
  }

  ~PreserveObj() {
    *_obj_ptr = _handle();
  }

  oop operator()() const {
    return _handle();
  }
};

bool MemAllocator::Allocation::check_out_of_memory() {
  JavaThread* THREAD = _thread; // For exception macros.
  assert(!HAS_PENDING_EXCEPTION, "Unexpected exception, will result in uninitialized storage");

  if (obj() != NULL) {
    return false;
  }

  const char* message = _overhead_limit_exceeded ? "GC overhead limit exceeded" : "Java heap space";
  if (!_thread->in_retryable_allocation()) {
    // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError support
    report_java_out_of_memory(message);

    if (JvmtiExport::should_post_resource_exhausted()) {
      JvmtiExport::post_resource_exhausted(
        JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR | JVMTI_RESOURCE_EXHAUSTED_JAVA_HEAP,
        message);
    }
    oop exception = _overhead_limit_exceeded ?
        Universe::out_of_memory_error_gc_overhead_limit() :
        Universe::out_of_memory_error_java_heap();
    THROW_OOP_(exception, true);
  } else {
    THROW_OOP_(Universe::out_of_memory_error_retry(), true);
  }
}

void MemAllocator::Allocation::verify_before() {
  // Clear unhandled oops for memory allocation.  Memory allocation might
  // not take out a lock if from tlab, so clear here.
  JavaThread* THREAD = _thread; // For exception macros.
  assert(!HAS_PENDING_EXCEPTION, "Should not allocate with exception pending");
  debug_only(check_for_valid_allocation_state());
  assert(!Universe::heap()->is_gc_active(), "Allocation during gc not allowed");
}

void MemAllocator::Allocation::verify_after() {
  NOT_PRODUCT(check_for_bad_heap_word_value();)
}

void MemAllocator::Allocation::check_for_bad_heap_word_value() const {
  MemRegion obj_range = _allocator.obj_memory_range(obj());
  HeapWord* addr = obj_range.start();
  size_t size = obj_range.word_size();
  if (CheckMemoryInitialization && ZapUnusedHeapArea) {
    for (size_t slot = 0; slot < size; slot += 1) {
      assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
             "Found badHeapWordValue in post-allocation check");
    }
  }
}

#ifdef ASSERT
void MemAllocator::Allocation::check_for_valid_allocation_state() const {
  // How to choose between a pending exception and a potential
  // OutOfMemoryError?  Don't allow pending exceptions.
  // This is a VM policy failure, so how do we exhaustively test it?
  assert(!_thread->has_pending_exception(),
         "shouldn't be allocating with pending exception");
  // Allocation of an oop can always invoke a safepoint.
  JavaThread::cast(_thread)->check_for_valid_safepoint_state();
}
#endif

void MemAllocator::Allocation::notify_allocation_jvmti_sampler() {
  // support for JVMTI VMObjectAlloc event (no-op if not enabled)
  JvmtiExport::vm_object_alloc_event_collector(obj());

  if (!JvmtiExport::should_post_sampled_object_alloc()) {
    // Sampling disabled
    return;
  }

  if (!_allocated_outside_tlab && _allocated_tlab_size == 0 && !_tlab_end_reset_for_sample) {
    // Sample if it's a non-TLAB allocation, or a TLAB allocation that either refills the TLAB
    // or expands it due to taking a sampler induced slow path.
    return;
  }

  // If we want to be sampling, protect the allocated object with a Handle
  // before doing the callback. The callback is done in the destructor of
  // the JvmtiSampledObjectAllocEventCollector.
  size_t bytes_since_last = 0;

  {
    PreserveObj obj_h(_thread, _obj_ptr);
    JvmtiSampledObjectAllocEventCollector collector;
    size_t size_in_bytes = _allocator._word_size * HeapWordSize;
    ThreadLocalAllocBuffer& tlab = _thread->tlab();

    if (!_allocated_outside_tlab) {
      bytes_since_last = tlab.bytes_since_last_sample_point();
    }

    _thread->heap_sampler().check_for_sampling(obj_h(), size_in_bytes, bytes_since_last);
  }

  if (_tlab_end_reset_for_sample || _allocated_tlab_size != 0) {
    // Tell tlab to forget bytes_since_last if we passed it to the heap sampler.
    _thread->tlab().set_sample_end(bytes_since_last != 0);
  }
}

void MemAllocator::Allocation::notify_allocation_low_memory_detector() {
  // support low memory notifications (no-op if not enabled)
  LowMemoryDetector::detect_low_memory_for_collected_pools();
}

void MemAllocator::Allocation::notify_allocation_jfr_sampler() {
  HeapWord* mem = cast_from_oop<HeapWord*>(obj());
  size_t size_in_bytes = _allocator._word_size * HeapWordSize;

  if (_allocated_outside_tlab) {
    AllocTracer::send_allocation_outside_tlab(obj()->klass(), mem, size_in_bytes, _thread);
  } else if (_allocated_tlab_size != 0) {
    // TLAB was refilled
    AllocTracer::send_allocation_in_new_tlab(obj()->klass(), mem, _allocated_tlab_size * HeapWordSize,
                                             size_in_bytes, _thread);
  }
}

void MemAllocator::Allocation::notify_allocation_dtrace_sampler(JavaThread* thread) {
  if (DTraceAllocProbes) {
    // support for Dtrace object alloc event (no-op most of the time)
    Klass* klass = obj()->klass();
    size_t word_size = _allocator._word_size;
    if (klass != NULL && klass->name() != NULL) {
      SharedRuntime::dtrace_object_alloc(thread, obj(), word_size);
    }
  }
}

void MemAllocator::Allocation::notify_allocation(JavaThread* thread) {
  notify_allocation_low_memory_detector();
  notify_allocation_jfr_sampler();
  notify_allocation_dtrace_sampler(thread);
  notify_allocation_jvmti_sampler();
}

HeapWord* MemAllocator::mem_allocate_outside_tlab(Allocation& allocation) const {
  allocation._allocated_outside_tlab = true;
  HeapWord* mem = Universe::heap()->mem_allocate(_word_size, &allocation._overhead_limit_exceeded);
  if (mem == NULL) {
    return mem;
  }

  NOT_PRODUCT(Universe::heap()->check_for_non_bad_heap_word_value(mem, _word_size));
  size_t size_in_bytes = _word_size * HeapWordSize;
  _thread->incr_allocated_bytes(size_in_bytes);

  return mem;
}

HeapWord* MemAllocator::mem_allocate_inside_tlab(Allocation& allocation) const {
  assert(UseTLAB, "should use UseTLAB");

  // Try allocating from an existing TLAB.
  HeapWord* mem = mem_allocate_inside_tlab_fast();
  if (mem != NULL) {
    return mem;
  }

  // Try refilling the TLAB and allocating the object in it.
  return mem_allocate_inside_tlab_slow(allocation);
}

HeapWord* MemAllocator::mem_allocate_inside_tlab_fast() const {
  return _thread->tlab().allocate(_word_size);
}

HeapWord* MemAllocator::mem_allocate_inside_tlab_slow(Allocation& allocation) const {
  HeapWord* mem = NULL;
  ThreadLocalAllocBuffer& tlab = _thread->tlab();

  if (JvmtiExport::should_post_sampled_object_alloc()) {
    tlab.set_back_allocation_end();
    mem = tlab.allocate(_word_size);

    // We set back the allocation sample point to try to allocate this, reset it
    // when done.
    allocation._tlab_end_reset_for_sample = true;

    if (mem != NULL) {
      return mem;
    }
  }

  // Retain tlab and allocate object in shared space if
  // the amount free in the tlab is too large to discard.
  if (tlab.free() > tlab.refill_waste_limit()) {
    tlab.record_slow_allocation(_word_size);
    return NULL;
  }

  // Discard tlab and allocate a new one.
  // To minimize fragmentation, the last TLAB may be smaller than the rest.
  size_t new_tlab_size = tlab.compute_size(_word_size);

  tlab.retire_before_allocation();

  if (new_tlab_size == 0) {
    return NULL;
  }

  // Allocate a new TLAB requesting new_tlab_size. Any size
  // between minimal and new_tlab_size is accepted.
  size_t min_tlab_size = ThreadLocalAllocBuffer::compute_min_size(_word_size);
  mem = Universe::heap()->allocate_new_tlab(min_tlab_size, new_tlab_size, &allocation._allocated_tlab_size);
  if (mem == NULL) {
    assert(allocation._allocated_tlab_size == 0,
           "Allocation failed, but actual size was updated. min: " SIZE_FORMAT
           ", desired: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
           min_tlab_size, new_tlab_size, allocation._allocated_tlab_size);
    return NULL;
  }
  assert(allocation._allocated_tlab_size != 0, "Allocation succeeded but actual size not updated. mem at: "
         PTR_FORMAT " min: " SIZE_FORMAT ", desired: " SIZE_FORMAT,
         p2i(mem), min_tlab_size, new_tlab_size);

  if (ZeroTLAB) {
    // ..and clear it.
    Copy::zero_to_words(mem, allocation._allocated_tlab_size);
  } else {
    // ...and zap just allocated object.
#ifdef ASSERT
    // Skip mangling the space corresponding to the object header to
    // ensure that the returned space is not considered parsable by
    // any concurrent GC thread.
    size_t hdr_size = oopDesc::header_size();
    Copy::fill_to_words(mem + hdr_size, allocation._allocated_tlab_size - hdr_size, badHeapWordVal);
#endif // ASSERT
  }

  tlab.fill(mem, mem + _word_size, allocation._allocated_tlab_size);
  return mem;
}

HeapWord* MemAllocator::mem_allocate_slow(Allocation& allocation) const {
  // Allocation of an oop can always invoke a safepoint.
  debug_only(JavaThread::cast(_thread)->check_for_valid_safepoint_state());

  if (UseTLAB) {
    // Try refilling the TLAB and allocating the object in it.
    HeapWord* mem = mem_allocate_inside_tlab_slow(allocation);
    if (mem != NULL) {
      return mem;
    }
  }

  return mem_allocate_outside_tlab(allocation);
}

HeapWord* MemAllocator::mem_allocate(Allocation& allocation) const {
  if (UseTLAB) {
    // Try allocating from an existing TLAB.
    HeapWord* mem = mem_allocate_inside_tlab_fast();
    if (mem != NULL) {
      return mem;
    }
  }

  return mem_allocate_slow(allocation);
}

oop MemAllocator::allocate() const {
  oop obj = NULL;
  {
    Allocation allocation(*this, &obj);
    HeapWord* mem = mem_allocate(allocation);
    if (mem != NULL) {
      obj = initialize(mem);
    } else {
      // The unhandled oop detector will poison local variable obj,
      // so reset it to NULL if mem is NULL.
      obj = NULL;
    }
  }
  return obj;
}

void MemAllocator::mem_clear(HeapWord* mem) const {
  assert(mem != NULL, "cannot initialize NULL object");
  const size_t hs = oopDesc::header_size();
  assert(_word_size >= hs, "unexpected object size");
  oopDesc::set_klass_gap(mem, 0);
  Copy::fill_to_aligned_words(mem + hs, _word_size - hs);
}

oop MemAllocator::finish(HeapWord* mem) const {
  assert(mem != NULL, "NULL object pointer");
  // May be bootstrapping
  oopDesc::set_mark(mem, markWord::prototype());
  // Need a release store to ensure array/class length, mark word, and
  // object zeroing are visible before setting the klass non-NULL, for
  // concurrent collectors.
  oopDesc::release_set_klass(mem, _klass);
  return cast_to_oop(mem);
}

oop ObjAllocator::initialize(HeapWord* mem) const {
  mem_clear(mem);
  return finish(mem);
}

MemRegion ObjArrayAllocator::obj_memory_range(oop obj) const {
  if (_do_zero) {
    return MemAllocator::obj_memory_range(obj);
  }
  ArrayKlass* array_klass = ArrayKlass::cast(_klass);
  const size_t hs = arrayOopDesc::header_size(array_klass->element_type());
  return MemRegion(cast_from_oop<HeapWord*>(obj) + hs, _word_size - hs);
}

oop ObjArrayAllocator::initialize(HeapWord* mem) const {
  // Set array length before setting the _klass field because a
  // non-NULL klass field indicates that the object is parsable by
  // concurrent GC.
  assert(_length >= 0, "length should be non-negative");
  if (_do_zero) {
    mem_clear(mem);
  }
  arrayOopDesc::set_length(mem, _length);
  return finish(mem);
}

oop ClassAllocator::initialize(HeapWord* mem) const {
  // Set oop_size field before setting the _klass field because a
  // non-NULL _klass field indicates that the object is parsable by
  // concurrent GC.
  assert(_word_size > 0, "oop_size must be positive.");
  mem_clear(mem);
  java_lang_Class::set_oop_size(mem, _word_size);
  return finish(mem);
}

quality94%

¤ Dauer der Verarbeitung: 0.6 Sekunden ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.