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