jmasa@4196: /*
jmasa@4196:  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
jmasa@4196:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jmasa@4196:  *
jmasa@4196:  * This code is free software; you can redistribute it and/or modify it
jmasa@4196:  * under the terms of the GNU General Public License version 2 only, as
jmasa@4196:  * published by the Free Software Foundation.
jmasa@4196:  *
jmasa@4196:  * This code is distributed in the hope that it will be useful, but WITHOUT
jmasa@4196:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jmasa@4196:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jmasa@4196:  * version 2 for more details (a copy is included in the LICENSE file that
jmasa@4196:  * accompanied this code).
jmasa@4196:  *
jmasa@4196:  * You should have received a copy of the GNU General Public License version
jmasa@4196:  * 2 along with this work; if not, write to the Free Software Foundation,
jmasa@4196:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jmasa@4196:  *
jmasa@4196:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
jmasa@4196:  * or visit www.oracle.com if you need additional information or have any
jmasa@4196:  * questions.
jmasa@4196:  *
jmasa@4196:  */
jmasa@4196: #ifndef SHARE_VM_MEMORY_METABLOCK_HPP
jmasa@4196: #define SHARE_VM_MEMORY_METABLOCK_HPP
jmasa@4196: 
jmasa@4196: // Metablock are the unit of allocation from a Chunk.  It is initialized
jmasa@4196: // with the size of the requested allocation.  That size is overwritten
jmasa@4196: // once the allocation returns.
jmasa@4196: //
jmasa@4196: // A Metablock may be reused by its SpaceManager but are never moved between
jmasa@4196: // SpaceManagers.  There is no explicit link to the Metachunk
jmasa@4196: // from which it was allocated.  Metablock may be deallocated and
jmasa@4196: // put on a freelist but the space is never freed, rather
jmasa@4196: // the Metachunk it is a part of will be deallocated when it's
jmasa@4196: // associated class loader is collected.
jmasa@4196: 
jmasa@4196: class Metablock VALUE_OBJ_CLASS_SPEC {
jmasa@4196:   friend class VMStructs;
jmasa@4196:  private:
jmasa@4196:   // Used to align the allocation (see below).
jmasa@4196:   union block_t {
jmasa@4196:     void* _data[3];
jmasa@4196:     struct header_t {
jmasa@4196:       size_t _word_size;
jmasa@4196:       Metablock* _next;
jmasa@4196:       Metablock* _prev;
jmasa@4196:     } _header;
jmasa@4196:   } _block;
jmasa@4196:   static size_t _min_block_byte_size;
jmasa@4196:   static size_t _overhead;
jmasa@4196: 
jmasa@4196:   typedef union block_t Block;
jmasa@4196:   typedef struct header_t Header;
jmasa@4196:   const Block* block() const { return &_block; }
jmasa@4196:   const Block::header_t* header() const { return &(block()->_header); }
jmasa@4196:  public:
jmasa@4196: 
jmasa@4196:   static Metablock* initialize(MetaWord* p, size_t word_size);
jmasa@4196: 
jmasa@4196:   // This places the body of the block at a 2 word boundary
jmasa@4196:   // because every block starts on a 2 word boundary.  Work out
jmasa@4196:   // how to make the body on a 2 word boundary if the block
jmasa@4196:   // starts on a arbitrary boundary.  JJJ
jmasa@4196: 
jmasa@4196:   size_t word_size() const  { return header()->_word_size; }
jmasa@4196:   void set_word_size(size_t v) { _block._header._word_size = v; }
jmasa@4196:   size_t size() const volatile { return _block._header._word_size; }
jmasa@4196:   void set_size(size_t v) { _block._header._word_size = v; }
jmasa@4196:   Metablock* next() const { return header()->_next; }
jmasa@4196:   void set_next(Metablock* v) { _block._header._next = v; }
jmasa@4196:   Metablock* prev() const { return header()->_prev; }
jmasa@4196:   void set_prev(Metablock* v) { _block._header._prev = v; }
jmasa@4196: 
jmasa@4196:   static size_t min_block_byte_size() { return _min_block_byte_size; }
jmasa@4196:   static size_t overhead() { return _overhead; }
jmasa@4196: 
jmasa@4196:   bool is_free()                 { return header()->_word_size != 0; }
jmasa@4196:   void clear_next()              { set_next(NULL); }
jmasa@4196:   void link_prev(Metablock* ptr) { set_prev(ptr); }
jmasa@4196:   uintptr_t* end()              { return ((uintptr_t*) this) + size(); }
jmasa@4196:   bool cantCoalesce() const     { return false; }
jmasa@4196:   void link_next(Metablock* ptr) { set_next(ptr); }
jmasa@4196:   void link_after(Metablock* ptr){
jmasa@4196:     link_next(ptr);
jmasa@4196:     if (ptr != NULL) ptr->link_prev(this);
jmasa@4196:   }
jmasa@4196: 
jmasa@4196:   // Should not be needed in a free list of Metablocks
jmasa@4196:   void markNotFree()            { ShouldNotReachHere(); }
jmasa@4196: 
jmasa@4196:   // Debug support
jmasa@4196: #ifdef ASSERT
jmasa@4196:   void* prev_addr() const { return (void*)&_block._header._prev; }
jmasa@4196:   void* next_addr() const { return (void*)&_block._header._next; }
jmasa@4196:   void* size_addr() const { return (void*)&_block._header._word_size; }
jmasa@4196: #endif
jmasa@4196:   bool verify_chunk_in_free_list(Metablock* tc) const { return true; }
jmasa@4196:   bool verify_par_locked() { return true; }
jmasa@4196: 
jmasa@4196:   void assert_is_mangled() const {/* Don't check "\*/}
jmasa@4196: };
jmasa@4196: #endif // SHARE_VM_MEMORY_METABLOCK_HPP