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Java example source code file (psPromotionLAB.cpp)

This example Java source code file (psPromotionLAB.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

assert, attempt, collectedheap\:\:parallelscavengeheap, heapword, heapwordsize\/sizeof, memregion, null, parallelscavengeheap, parallelscavengeheap\*, plab, psoldgen, pspromotionlab\:\:flush, pspromotionlab\:\:initialize, sanity

The psPromotionLAB.cpp Java example source code

/*
 * Copyright (c) 2002, 2010, 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 "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
#include "gc_implementation/parallelScavenge/psPromotionLAB.hpp"
#include "gc_implementation/shared/mutableSpace.hpp"
#include "oops/oop.inline.hpp"

size_t PSPromotionLAB::filler_header_size;

// This is the shared initialization code. It sets up the basic pointers,
// and allows enough extra space for a filler object. We call a virtual
// method, "lab_is_valid()" to handle the different asserts the old/young
// labs require.
void PSPromotionLAB::initialize(MemRegion lab) {
  assert(lab_is_valid(lab), "Sanity");

  HeapWord* bottom = lab.start();
  HeapWord* end    = lab.end();

  set_bottom(bottom);
  set_end(end);
  set_top(bottom);

  // Initialize after VM starts up because header_size depends on compressed
  // oops.
  filler_header_size = align_object_size(typeArrayOopDesc::header_size(T_INT));

  // We can be initialized to a zero size!
  if (free() > 0) {
    if (ZapUnusedHeapArea) {
      debug_only(Copy::fill_to_words(top(), free()/HeapWordSize, badHeapWord));
    }

    // NOTE! We need to allow space for a filler object.
    assert(lab.word_size() >= filler_header_size, "lab is too small");
    end = end - filler_header_size;
    set_end(end);

    _state = needs_flush;
  } else {
    _state = zero_size;
  }

  assert(this->top() <= this->end(), "pointers out of order");
}

// Fill all remaining lab space with an unreachable object.
// The goal is to leave a contiguous parseable span of objects.
void PSPromotionLAB::flush() {
  assert(_state != flushed, "Attempt to flush PLAB twice");
  assert(top() <= end(), "pointers out of order");

  // If we were initialized to a zero sized lab, there is
  // nothing to flush
  if (_state == zero_size)
    return;

  // PLAB's never allocate the last aligned_header_size
  // so they can always fill with an array.
  HeapWord* tlab_end = end() + filler_header_size;
  typeArrayOop filler_oop = (typeArrayOop) top();
  filler_oop->set_mark(markOopDesc::prototype());
  filler_oop->set_klass(Universe::intArrayKlassObj());
  const size_t array_length =
    pointer_delta(tlab_end, top()) - typeArrayOopDesc::header_size(T_INT);
  assert( (array_length * (HeapWordSize/sizeof(jint))) < (size_t)max_jint, "array too big in PSPromotionLAB");
  filler_oop->set_length((int)(array_length * (HeapWordSize/sizeof(jint))));

#ifdef ASSERT
  // Note that we actually DO NOT want to use the aligned header size!
  HeapWord* elt_words = ((HeapWord*)filler_oop) + typeArrayOopDesc::header_size(T_INT);
  Copy::fill_to_words(elt_words, array_length, 0xDEAABABE);
#endif

  set_bottom(NULL);
  set_end(NULL);
  set_top(NULL);

  _state = flushed;
}

bool PSPromotionLAB::unallocate_object(HeapWord* obj, size_t obj_size) {
  assert(Universe::heap()->is_in(obj), "Object outside heap");

  if (contains(obj)) {
    HeapWord* object_end = obj + obj_size;
    assert(object_end == top(), "Not matching last allocation");

    set_top(obj);
    return true;
  }

  return false;
}

// Fill all remaining lab space with an unreachable object.
// The goal is to leave a contiguous parseable span of objects.
void PSOldPromotionLAB::flush() {
  assert(_state != flushed, "Attempt to flush PLAB twice");
  assert(top() <= end(), "pointers out of order");

  if (_state == zero_size)
    return;

  HeapWord* obj = top();

  PSPromotionLAB::flush();

  assert(_start_array != NULL, "Sanity");

  _start_array->allocate_block(obj);
}

#ifdef ASSERT

bool PSYoungPromotionLAB::lab_is_valid(MemRegion lab) {
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  MutableSpace* to_space = heap->young_gen()->to_space();
  MemRegion used = to_space->used_region();
  if (used.contains(lab)) {
    return true;
  }

  return false;
}

bool PSOldPromotionLAB::lab_is_valid(MemRegion lab) {
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  assert(_start_array->covered_region().contains(lab), "Sanity");

  PSOldGen* old_gen = heap->old_gen();
  MemRegion used = old_gen->object_space()->used_region();

  if (used.contains(lab)) {
    return true;
  }

  return false;
}

#endif /* ASSERT */

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