1 /*
   2  * Copyright (c) 2012, 2016, 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 "memory/allocation.hpp"
  27 #include "memory/metachunk.hpp"
  28 #include "utilities/align.hpp"
  29 #include "utilities/copy.hpp"
  30 #include "utilities/debug.hpp"
  31 
  32 class VirtualSpaceNode;
  33 
  34 size_t Metachunk::object_alignment() {
  35   // Must align pointers and sizes to 8,
  36   // so that 64 bit types get correctly aligned.
  37   const size_t alignment = 8;
  38 
  39   // Make sure that the Klass alignment also agree.
  40   STATIC_ASSERT(alignment == (size_t)KlassAlignmentInBytes);
  41 
  42   return alignment;
  43 }
  44 
  45 size_t Metachunk::overhead() {
  46   return align_up(sizeof(Metachunk), object_alignment()) / BytesPerWord;
  47 }
  48 
  49 // Metachunk methods
  50 
  51 Metachunk::Metachunk(size_t word_size,
  52                      VirtualSpaceNode* container)
  53     : Metabase<Metachunk>(word_size),
  54     _top(NULL),
  55     _container(container)
  56 {
  57   _top = initial_top();
  58 #ifdef ASSERT
  59   set_is_tagged_free(false);
  60   mangle(uninitMetaWordVal);
  61 #endif
  62 }
  63 
  64 MetaWord* Metachunk::allocate(size_t word_size) {
  65   MetaWord* result = NULL;
  66   // If available, bump the pointer to allocate.
  67   if (free_word_size() >= word_size) {
  68     result = _top;
  69     _top = _top + word_size;
  70   }
  71   return result;
  72 }
  73 
  74 // _bottom points to the start of the chunk including the overhead.
  75 size_t Metachunk::used_word_size() const {
  76   return pointer_delta(_top, bottom(), sizeof(MetaWord));
  77 }
  78 
  79 size_t Metachunk::free_word_size() const {
  80   return pointer_delta(end(), _top, sizeof(MetaWord));
  81 }
  82 
  83 void Metachunk::print_on(outputStream* st) const {
  84   st->print_cr("Metachunk:"
  85                " bottom " PTR_FORMAT " top " PTR_FORMAT
  86                " end " PTR_FORMAT " size " SIZE_FORMAT,
  87                p2i(bottom()), p2i(_top), p2i(end()), word_size());
  88   if (Verbose) {
  89     st->print_cr("    used " SIZE_FORMAT " free " SIZE_FORMAT,
  90                  used_word_size(), free_word_size());
  91   }
  92 }
  93 
  94 #ifndef PRODUCT
  95 void Metachunk::mangle(juint word_value) {
  96   // Overwrite the payload of the chunk and not the links that
  97   // maintain list of chunks.
  98   HeapWord* start = (HeapWord*)initial_top();
  99   size_t size = word_size() - overhead();
 100   Copy::fill_to_words(start, size, word_value);
 101 }
 102 #endif // PRODUCT
 103 
 104 void Metachunk::verify() {
 105 #ifdef ASSERT
 106   // Cannot walk through the blocks unless the blocks have
 107   // headers with sizes.
 108   assert(bottom() <= _top &&
 109          _top <= (MetaWord*)end(),
 110          "Chunk has been smashed");
 111 #endif
 112   return;
 113 }
 114